Decoding OBD2 Live Data: A Comprehensive Guide to Parameter Identifiers for Vehicle Diagnostics

Understanding your vehicle’s health is becoming increasingly accessible thanks to On-Board Diagnostics II (OBD2) systems. At the heart of this system is Obd2 Live Data, a stream of real-time information that your car’s computer broadcasts about its operating conditions. This invaluable data, accessed through an OBD2 scanner, empowers car enthusiasts and professionals alike to monitor performance, diagnose issues, and ensure optimal vehicle maintenance.

This comprehensive guide dives deep into the world of OBD2 Parameter Identifiers (PIDs), the specific data points that constitute live data. We will break down each PID, explaining what it measures, why it’s important, and how understanding these parameters can transform your approach to vehicle diagnostics.

Vehicle Operation Parameters

These PIDs provide insights into the fundamental operational aspects of your vehicle’s engine and driving dynamics.

Engine RPM (Revolutions Per Minute)

Engine RPM measures how many revolutions the engine crankshaft completes in a minute. It’s a fundamental indicator of engine speed and is crucial for understanding:

Engine Load: Higher RPM generally indicates higher engine load.
Gear Selection: RPM changes with gear shifts, indicating proper transmission function.
Idle Stability: A steady RPM at idle is essential for smooth engine operation.
Performance Issues: Unusual RPM fluctuations or readings can point to problems in the fuel system, ignition, or engine control.

Vehicle Speed

This PID simply reports the current speed of your vehicle. While seemingly straightforward, it’s vital for:

Speedometer Verification: Comparing OBD2 speed with your speedometer reading can identify discrepancies.
Cruise Control Diagnostics: Monitoring speed stability during cruise control operation.
ABS/Traction Control Analysis: Speed data is essential for these systems to function correctly, and discrepancies can indicate sensor issues.

Engine Coolant Temperature

Measured by a sensor in the engine, coolant temperature is critical for regulating engine heat and preventing overheating. Monitoring this PID helps to:

Warm-up Monitoring: Track how quickly your engine reaches its optimal operating temperature.
Overheating Detection: High coolant temperatures are a primary indicator of potential overheating issues.
Thermostat Function: Consistent temperature readings within the normal range suggest a properly functioning thermostat.
Cooling System Diagnosis: Problems with radiators, fans, or water pumps can be identified through abnormal coolant temperature readings.

Engine Oil Temperature

Oil temperature sensors, often thermocouples, thermistors, or RTDs, monitor the temperature of the engine oil. Maintaining optimal oil temperature is crucial because:

Lubrication Efficiency: Oil viscosity and lubrication properties are temperature-dependent. Too hot or too cold oil can reduce engine protection.
Engine Wear: Excessive oil temperature can accelerate engine wear and tear.
Performance Optimization: Monitoring oil temperature can be important for high-performance driving and towing applications.

Ambient Air Temperature

This PID reflects the outside air temperature, measured by a sensor typically located in the front of the vehicle. It’s relevant for:

Engine Performance Adjustment: The engine control unit (ECU) uses ambient temperature to adjust air-fuel mixture and ignition timing for optimal performance in varying conditions.
Climate Control System: Ambient temperature is a key input for automatic climate control systems.

Barometric Pressure

Also known as atmospheric pressure, barometric pressure is measured by a BARO sensor. The ECU uses this information to:

Altitude Compensation: Air density changes with altitude, affecting air-fuel ratios. The BARO sensor helps the ECU adjust for these changes.
Fuel Trim and Timing Adjustment: Accurate barometric pressure readings are essential for precise fuel and ignition timing control.
Performance Diagnostics: Unexpectedly low barometric pressure readings might suggest sensor malfunctions. Note: Average sea level barometric pressure is 14.7 PSI.

Accelerator Pedal Position

Sensors on the accelerator pedal track its position, indicating driver demand for power. This PID is crucial for:

Throttle Control Analysis: Correlating accelerator pedal position with throttle position helps diagnose issues in the electronic throttle control system.
Driver Input Monitoring: Understanding how the driver is interacting with the vehicle.
Performance Diagnostics: Lagging or inconsistent accelerator pedal readings can point to sensor or wiring problems.

Relative Accelerator Pedal Position

This PID refines the accelerator pedal position reading by considering sensor output voltages. It’s important to note that:

Sensor Calibration: Due to sensor tolerances and calibration, the reading may not always reach 100% even when the pedal is fully depressed.
Multiple Sensor Averaging: Some vehicles use multiple sensors, and this PID may display an average value.

Commanded Throttle Actuator

This PID shows the throttle position requested by the ECU based on the accelerator pedal input and other factors. It’s a key parameter for:

Electronic Throttle Control (ETC) Diagnostics: Comparing commanded throttle position with actual throttle position (see below) can reveal issues with the ETC system, such as actuator problems or control module faults.
Engine Load Management: The ECU uses throttle control to manage engine load and optimize fuel efficiency.

Relative Throttle Position

Relative throttle position compares the current throttle position to a learned closed position. This is important because:

Carbon Buildup Compensation: Carbon deposits in the throttle body can affect throttle behavior over time. This PID reflects adjustments made to compensate for these changes.
Throttle Body Health: Significant deviations in relative throttle position from expected values can indicate the need for throttle body cleaning or maintenance.

Absolute Throttle Position

This PID represents the actual physical opening of the throttle valve, ranging from 0% (fully closed) to 100% (fully open). It’s essential for:

Verifying Throttle Operation: Ensuring the throttle body is responding correctly to ECU commands.
Performance Diagnostics: Restricted throttle opening can limit engine power and performance.

Control Module Voltage

This PID monitors the voltage supplied to the engine control unit (ECU). It’s crucial because:

Power Supply Integrity: The ECU requires a stable and adequate voltage supply to function correctly.
Electrical System Diagnostics: Low or fluctuating control module voltage can indicate issues with the battery, alternator, or wiring. Note: This is not the same as battery voltage directly.

Hybrid Battery Pack Remaining Life

For hybrid vehicles, this PID indicates the remaining charge percentage in the high-voltage hybrid battery pack. It’s important for:

Hybrid System Monitoring: Tracking battery health and charge status.
Range Estimation: While not a direct range indicator, battery percentage is a contributing factor.
Battery Health Assessment: Significant degradation in remaining life over time can suggest battery aging or problems. Note: Standard OBD2 typically doesn’t provide individual cell data.

Hybrid/EV Vehicle System Status

This comprehensive PID provides status information for various aspects of hybrid and electric vehicle (EV) systems, including:

HEV Charging State:
- Charge Sustaining Mode (CSM): Maintaining a constant state of charge, typical for non-plug-in hybrids (HEVs).
- Charge Depletion Mode (CDM): Targeting lower states of charge, common in plug-in hybrid electric vehicles (PHEVs).
- Non-PHEVs permanent Charge Sustaining Mode: HEVs generally operate in CSM.
HEV Battery Voltage: Voltage of the high-voltage battery pack, ranging from 0V to 1024V.
HEV Battery Current: Current flow in or out of the battery pack. Negative values indicate charging; positive values indicate discharging. Range: -3300 Amps to 3300 Amps.

Calculated Engine Load Value

This PID represents the calculated engine load as a percentage. It’s derived from the Mass Air Flow (MAF) sensor reading and peak airflow potential. Understanding engine load is crucial for:

Engine Stress Assessment: Higher load values indicate greater stress on engine components.
Fuel Efficiency Analysis: Engine load is a significant factor in fuel consumption.
Performance Tuning: Load data is essential for optimizing engine performance and efficiency. Note: Altitude correction is applied to peak airflow calculations.

Absolute Load Value

Similar to Calculated Engine Load, Absolute Load Value is a normalized percentage representing air mass per intake stroke relative to the maximum air mass at 100% throttle. Key points include:

Air Intake Efficiency: Reflects how efficiently the engine is drawing in air.
Engine Condition Indication: Deviations from expected values can suggest issues with air intake restrictions or engine breathing. Note: Values vary based on vehicle state (idle, parking, accessories).

Driver’s Demand Engine – Percent Torque

This PID represents the percentage of maximum available engine torque requested by the driver, based on accelerator pedal input, cruise control, and transmission demands. It reflects:

Driver Intent: How much power the driver is requesting from the engine.
Torque Management System: Indicates how the engine control system is interpreting driver input and translating it into torque output. Note: External factors like traction control and ABS do not directly affect this value.

Actual Engine – Percent Torque

Also known as Indicated Torque, this PID shows the current percentage of the total available engine torque. It considers:

Net Brake Torque: Torque available at the wheels after drivetrain losses.
Friction Torque: Torque required to overcome internal engine friction.
Real-time Torque Output: Reflects the engine’s actual torque production at any given moment.

Engine Friction – Percent Torque

This PID represents the percentage of maximum engine torque required to overcome internal engine friction and operate the engine without any external load. It’s useful for:

Engine Health Assessment: Increased friction torque over time might indicate engine wear.
Efficiency Analysis: Understanding the proportion of engine torque being used to overcome internal losses.
Baseline Performance Measurement: Provides a reference point for engine performance analysis.

Engine Reference Torque

This PID represents a fixed torque rating considered as 100% for Actual Engine Percentage Torque and other torque-related parameters. Key characteristics:

Constant Value: Engine Reference Torque is a static value that doesn’t change over time.
Normalization Baseline: Serves as a reference point for interpreting percentage-based torque PIDs.

Engine Percent Torque Data

This PID is a broader parameter used when vehicle condition changes can affect the torque reference point. It provides a more dynamic perspective on engine torque behavior.

Auxiliary Input/Output

This composite PID provides status details for various vehicle systems, including:

Power Take Off (PTO) and Glow Plug Lamp Status (On/Off): For vehicles equipped with PTO systems and diesel engines.
Automatic Transmission Status (Park/Neutral or Drive/Reverse): Gear selector position for automatic transmissions.
Manual Transmission Status (Neutral/Clutch In or In Gear): Gear and clutch status for manual transmissions.
Recommended Transmission Gear (1 to 15 Status): Suggests the optimal gear for current driving conditions (if supported).

Exhaust Gas Temperature (EGT)

EGT sensors are strategically placed in the exhaust system to monitor temperature and protect components from overheating. Critical locations include:

Turbocharger: Preventing turbocharger damage from excessive heat.
Catalytic Converter: Ensuring optimal catalytic converter operating temperature and preventing thermal damage.
Diesel Particulate Filter (DPF): Monitoring DPF temperature during regeneration cycles.
NOx Reduction System Components: Protecting components in advanced emissions control systems.

Engine Exhaust Flow Rate

This PID calculates the flow rate of the exhaust gases, reflecting the volume of the air-fuel mixture being combusted. Calculation factors include:

Exhaust Temperature: Temperature of the exhaust gases.
Volumetric Efficiency: Engine’s efficiency in filling cylinders with air-fuel mixture.
Engine Size: Displacement of the engine.
Flywheel RPM: Engine speed.

Exhaust Pressure

This PID measures exhaust pressure, typically displayed as an absolute pressure value when the engine is running. It’s useful for:

Exhaust System Diagnostics: High exhaust pressure can indicate restrictions in the exhaust system, such as a clogged catalytic converter or muffler.
Turbocharger System Analysis: Exhaust pressure is relevant to turbocharger performance. Note: Data may be reported from one or two exhausts depending on vehicle configuration.

Manifold Surface Temperature

This PID measures the temperature of the exhaust manifold’s outer surface. It provides an additional temperature reading point in the exhaust system, useful for thermal analysis.

Timing Advance for #1 Cylinder

This PID indicates the ignition timing advance for cylinder #1, representing the angle of crankshaft rotation before Top Dead Center (TDC) when the spark plug fires. Understanding timing advance is crucial for:

Ignition System Diagnostics: Abnormal timing advance readings can point to issues with the ignition system or knock sensors.
Engine Performance Optimization: Ignition timing is a key factor in engine power and efficiency. Note: Positive value = delayed spark; negative value = spark before TDC.

Engine Run Time

This PID provides a comprehensive report of engine operating time, including:

Engine Run Time in Seconds: Total accumulated engine run time.
Engine Idle Time In Seconds: Time spent idling.
Engine Run Time when PTO is Engaged: Run time with Power Take-Off system active.

Run Time Since Engine Start

This PID simply measures the total run time in seconds since the engine was last started.

Time Run with MIL On

This PID tracks the total engine run time since the Malfunction Indicator Lamp (MIL), or check engine light, was activated. It’s distinct from total elapsed time and specifically measures:

Diagnostic Event Duration: How long the vehicle has been operated with an active fault code. Note: Value starts counting when the MIL illuminates.

Distance Traveled while MIL is Activated

This PID records the total distance traveled since the check engine light came on. It provides context for:

Fault Condition Mileage: How many miles the vehicle has been driven with an active fault. Note: Resets when codes are cleared or battery is disconnected.

Time since Trouble Codes Cleared

This PID measures the total engine run time since diagnostic trouble codes (DTCs) were last cleared, either by an OBD2 scan tool or battery disconnection.

Distance Traveled Since Codes Cleared

This PID tracks the total distance driven since DTCs were cleared. It’s useful for:

Post-Diagnostic Monitoring: Tracking vehicle behavior after code clearing to see if issues recur. Note: Doesn’t reset when non-engine codes are cleared.

Warm-ups Since Codes Cleared

This PID counts the number of engine warm-up cycles completed since codes were cleared. A warm-up cycle is defined as:

Coolant Temperature Increase: Coolant reaching at least 40°F after startup and then reaching at least 170°F.
Drive Cycle Tracking: Provides a measure of drive cycles since the last code reset.

Fuel & Air Parameters

These PIDs are crucial for understanding the engine’s air-fuel mixture, fuel delivery system, and overall combustion efficiency.

Fuel System Status

This PID reports the operating mode of the fuel system, which can be in:

Open Loop Mode: The ECU uses pre-programmed air-fuel ratios based on sensor inputs but without feedback from the oxygen sensors. Used during engine warm-up or high-load conditions.
Closed Loop Mode: The ECU actively adjusts the air-fuel ratio based on feedback from the oxygen sensors to maintain the ideal stoichiometric ratio. Used for normal operating conditions.

Oxygen Sensor Voltage

Oxygen sensors measure the amount of oxygen in the exhaust gas. Voltage readings indicate:

Air-Fuel Ratio: Voltage typically ranges from 0.1V to 0.9V.
Sensor Functionality: Readings outside this range or erratic fluctuations can indicate sensor problems.
Lean vs. Rich Mixture: Low voltage (around 0.1V) suggests a lean mixture (excess oxygen); high voltage (around 0.9V) suggests a rich mixture (low oxygen).

Oxygen Sensor Equivalence Ratio (Lambda)

Also known as the Lambda sensor, this PID provides a more direct measure of the air-fuel ratio relative to the stoichiometric ideal (Lambda = 1).

Closed Loop Feedback: In closed loop, this sensor provides crucial feedback for ECU fuel adjustments.
Open Loop Monitoring: In open loop, the sensor still provides readings, but the ECU doesn’t actively use them for fuel trim.

Oxygen Sensor Current

This PID measures the current flow within the oxygen sensor, which is directly related to the air-fuel ratio.

Balanced Mixture (0 mA): Indicates a near-stoichiometric air-fuel ratio.
Lean Mixture (Positive Current): Excess air in the mixture.
Rich Mixture (Negative Current): Excess fuel in the mixture.

Short Term Fuel Trim (STFT)

STFT represents immediate, short-term adjustments the ECU makes to the air-fuel mixture based on oxygen sensor feedback.

Real-time Correction: Reflects the ECU’s instantaneous attempts to maintain the ideal air-fuel ratio.
Lean Correction (Positive STFT): ECU is adding fuel to compensate for a lean mixture.
Rich Correction (Negative STFT): ECU is reducing fuel to compensate for a rich mixture.

Long Term Fuel Trim (LTFT)

LTFT represents longer-term, learned adjustments to the base fuel delivery strategy. It compensates for gradual changes in engine components or operating conditions.

Adaptive Learning: LTFT values are stored in the ECU’s memory and adapt over time.
Underlying Issues: Consistently high or low LTFT values can indicate underlying problems like vacuum leaks, fuel pressure issues, or MAF sensor inaccuracies. Note: LTFT updates take seconds and are stored in ECM memory.

Commanded Equivalence Ratio (CER)

CER, also known as lambda, indicates the desired air-fuel ratio requested by the ECU.

Wide Range O2 Sensors: CER is displayed in both open and closed loop modes for vehicles with wideband oxygen sensors.
Conventional O2 Sensors: CER is typically displayed in open loop mode; in closed loop, it often reads 1.0 (stoichiometric).

Mass Air Flow (MAF) Rate

MAF rate measures the mass of air entering the engine per unit of time (grams per second). It’s a crucial input for calculating fuel delivery.

Air Intake Volume: Directly reflects the amount of air being drawn into the engine.
Engine Load and Performance: MAF readings increase with engine load and RPM.
MAF Sensor Diagnostics: Out-of-range or erratic MAF readings can indicate sensor problems. Note: Typical idle range: 2-7 g/s; 2500 rpm range: 15-25 g/s. Refer to manufacturer specs for your vehicle.

Intake Air Temperature (IAT)

IAT measures the temperature of the air entering the engine. Vehicles may have multiple IAT sensors for different purposes:

Engine Air Intake Measurement: Primary IAT sensor for air-fuel ratio calculations.
Climate Control System Input: IAT sensor for automatic climate control.
Ambient Air Temperature Measurement: Dedicated ambient temperature sensor.

Intake Manifold Absolute Pressure (MAP)

MAP sensor measures the absolute pressure within the intake manifold. It’s used to:

Air Density Measurement: MAP sensor readings, along with IAT, help determine air density for accurate fuel calculations.
Vacuum Indication: MAP readings reflect intake manifold vacuum, which is related to engine load and throttle position. Note: Running engine: 18-20 “Hg vacuum; Idle engine: 0-20 “Hg vacuum.

Fuel Pressure (Gauge)

This PID reports fuel pressure as a gauge pressure value. Gauge pressure measures pressure relative to atmospheric pressure.

Fuel Delivery System Monitoring: Ensuring adequate fuel pressure is essential for proper engine operation. Note: 0 gauge pressure indicates atmospheric pressure.

Fuel Rail Pressure

Similar to Fuel Pressure (Gauge), this PID reports fuel pressure in the fuel rail as a gauge pressure value.

Fuel Rail Pressure (Absolute)

This PID reports fuel rail pressure as an absolute pressure value. Absolute pressure is measured relative to a perfect vacuum.

True Pressure Reading: Provides a more fundamental pressure measurement. Note: 0 fuel rail pressure will read as ambient pressure (approx. 14.7 psi or 101.3 kPa).

Fuel Rail Pressure (relative to manifold vacuum)

This PID reports fuel pressure relative to the intake manifold vacuum. This can be useful for diagnosing fuel pressure regulators that are vacuum-referenced.

Alcohol Fuel %

This PID indicates the percentage of ethanol or alcohol content in the fuel, as measured by the engine computer.

Flex-Fuel Vehicle Monitoring: Crucial for vehicles designed to run on varying blends of gasoline and ethanol (e.g., E85). Example: E85 blend will read approximately 85%.

Fuel Level Input

This PID reports the percentage of fuel remaining in the fuel tank, based on the fuel level sensor.

Engine Fuel Rate

This PID provides a near-instantaneous fuel consumption rate, typically in Liters or Gallons per hour.

Fuel Efficiency Monitoring: Real-time fuel consumption data. Note: Calculated by ECM over 1000ms intervals; excludes fuel used by diesel aftertreatment systems.

Cylinder Fuel Rate

This PID reports the calculated amount of fuel injected per cylinder during the most recent intake stroke, measured in mg/stroke. Provides cylinder-specific fuel delivery information.

Fuel System Percentage Use

This PID shows the percentage of total fuel usage for each cylinder bank (up to four banks). It can also display data for multiple fuel systems (e.g., diesel & CNG) if supported.

Fuel Injection Timing

This PID indicates the crankshaft angle (in degrees Before Top Dead Center – BTDC) at which fuel injection begins.

Injection Timing Control: Reflects the ECU’s control over fuel injection timing. Note: Positive angle = injection before TDC; negative angle = injection after TDC.

Fuel System Control

This PID reports status information for various fuel system control loops in diesel vehicles, including:

Fuel Pressure Control (Open/Closed Loop): Control strategy for fuel pressure regulation.
Fuel Injection Quantity (Open/Closed Loop): Control strategy for fuel injection amount.
Fuel Injection Timing (Open/Closed Loop): Control strategy for fuel injection timing.
Idle Fuel Balance/Contribution (Open/Closed Loop): Control strategy for balancing fuel delivery at idle. Note: Systems 1 & 2 refer to potentially separate fuel systems, system 2 may not always be in use.

Fuel Pressure Control System

This PID provides detailed data for up to two fuel rails, including:

Commanded Rail Pressure: Target fuel pressure set by the ECU.
Actual Rail Pressure: Measured fuel pressure in the rail.
Temperature: Fuel temperature in the rail. Note: Pressure is reported as gauge pressure.

Injection Pressure Control System

In some diesel engines with high-pressure oil injection (HEUI), this PID monitors the oil pressure side of the fuel system, reporting:

Commanded Control Pressure Rail A/B: Target oil pressure for injection control.
Actual Pressure Rail A/B: Measured oil pressure.

Boost Pressure Control

For turbocharged vehicles, this PID provides boost pressure information, including:

ECM Commanded Boost Pressure: Target boost pressure set by the ECU.
Actual Boost Pressure: Measured boost pressure. Note: All data is reported in absolute pressure. Gauge pressure is typically used when discussing boost levels (e.g., 10 psi of boost = 24.7 psi absolute pressure at sea level). Open/Closed Loop and Fault states are also reported.

Turbocharger RPM

This PID measures the rotational speed of the turbocharger turbine, either for one or both turbos.

Turbo Performance Monitoring: Track turbocharger speed and response. Note: Maximum value is 655,350 rpm.

Turbocharger Temperature

This PID reports various turbocharger temperatures:

Compressor Inlet Temperature: Air temperature before the turbocharger.
Compressor Outlet Temperature: Air temperature after the turbocharger (should be significantly higher).
Turbine Inlet Temperature: Exhaust temperature before the turbine.
Turbine Outlet Temperature: Exhaust temperature after the turbine. Note: Charge air temp range: -40 to 215 °C; Exhaust temp range: -40 to 6513.5 °C.

Turbocharger Compressor Inlet Pressure Sensor

This PID measures pressure at the turbocharger inlet, either for one or two turbos. Reported as absolute pressure.

Variable Geometry Turbo (VGT) Control

For vehicles with VGTs, this PID reports vane position and control status:

Commanded VGT Position: Target vane position set by the ECU (0% = max bypass; 100% = max boost).
Actual VGT Vane Position: Measured vane position.
VGT Control Status (Open/Closed Loop/Fault): Indicates control mode and fault status.

Wastegate Control

For electronic wastegate systems, this PID reports wastegate position and control status:

Commanded Wastegate Position: Target wastegate position (0% = fully closed; 100% = max bypass).
Actual Wastegate Position: Measured wastegate position.

Charge Air Cooler Temperature (CACT)

This PID reports temperatures from up to four charge air cooler (intercooler) sensors:

Bank 1 Sensor 1/2, Bank 2 Sensor 1/2: Sensor locations may vary; refer to factory manual for specific mapping.

Emissions Control Parameters

These PIDs provide insights into the operation and performance of your vehicle’s emissions control systems, crucial for environmental compliance and vehicle health.

Commanded EGR

This PID indicates the desired opening percentage of the Exhaust Gas Recirculation (EGR) valve, as commanded by the ECU (0% = closed; 100% = open).

EGR Error

This PID reports the percentage difference between the commanded EGR opening and the actual EGR valve position.

EGR System Accuracy: Indicates how closely the EGR system is following ECU commands. Note: EGR error calculation and “undefined” behavior when commanded EGR is 0%.

Commanded Diesel Intake Air Flow Control

Also known as EGR Throttle, this PID reports the position of the intake air flow throttle plate used in some newer diesel engines for EGR control.

EGR Throttle Position: Commanded and actual positions of primary and secondary EGR throttles (if equipped).

Exhaust Gas Recirculation Temperature

This PID reports up to four EGR temperature values, often related to EGR cooler stages:

EGRTA – Bank 1 Pre-Cooler, EGRTB – Bank 1 Post-Cooler, EGRTC – Bank 2 Pre-Cooler, EGRTD – Bank 2 Post-Cooler.

EVAP System Vapor Pressure

This PID reports the gauge pressure within the Evaporative Emission Control (EVAP) system, measured from a sensor in the fuel tank or EVAP lines.

Absolute Evap System Vapor Pressure

This PID reports the absolute pressure in the EVAP system. Note: 14.7 psi or 101.3 kPa indicates 0 gauge pressure.

Commanded Evaporative Purge

This PID indicates the requested purge flow rate for the EVAP system, as commanded by the ECU (0% = closed; 100% = max flow).

Catalyst Temperature

This PID reports the temperature of the catalytic converter(s).

Bank # Sensor #: Bank 1 is typically the side with cylinder #1; Sensor #1 is pre-cat, Sensor #2 is post-cat.

Diesel Aftertreatment Status

This hybrid PID provides comprehensive status information about diesel aftertreatment systems, including:

DPF Regeneration Status (Active/Not Active): Indicates if DPF regeneration is currently in progress.
DPF Regeneration Type (Passive/Active): Type of regeneration being performed.
NOx Absorber Regen Status (Active/Not Active): Status of NOx absorber regeneration.
NOx Absorber Desulfurization Status (Active/Not Active): Status of NOx absorber desulfurization.
Normalized Trigger for DPF Regen (%): Percentage until the next DPF regeneration event.
Average Time Between DPF Regens: Average regeneration interval (time-based).
Average Distance Between DPF Regens: Average regeneration interval (distance-based).

Diesel Exhaust Fluid Sensor Data

This PID reports information from the Diesel Exhaust Fluid (DEF) system, including:

DEF Type (Urea too high/low, Straight diesel, Proper DEF, Sensor fault): Indicates DEF fluid quality.
DEF Concentration (%): Urea concentration (target ~32.5%).
DEF Tank Temperature: DEF tank temperature.
DEF Tank Level: DEF tank level percentage. Note: Tank level reporting may be discrete rather than progressive.

Diesel Particulate Filter (DPF)

This PID provides DPF pressure data:

Inlet Pressure, Outlet Pressure, Differential Pressure: Pressure readings at DPF inlet and outlet, and the pressure difference across the filter. Increased differential pressure indicates soot accumulation. Bank 1 vs. Bank 2 designation.

Diesel Particulate Filter (DPF) Temperature

This PID reports DPF temperatures:

Inlet Temperature, Outlet Temperature: Temperature readings at DPF inlet and outlet. Bank 1 vs. Bank 2 designation.

NOx Sensor

This hybrid PID reports NOx concentration levels (ppm) from up to four NOx sensors:

Bank # Sensor #: Bank 1 is typically the side with cylinder #1; Sensor #1 is pre-NOx adsorber, Sensor #2 is post-NOx adsorber.

NOx Control System

This hybrid PID provides data related to the NOx adsorption system:

Average Reagent Consumption Rate: Average DEF/reagent consumption rate.
Average Demanded Consumption Rate: Target reagent consumption rate.
Reagent Tank Level (%): DEF/reagent tank level. Note: Tank level reporting may be discrete.
NOx Warning Indicator Time: Engine run time since NOx warning light activation.

NOx Sensor Corrected Data

This PID reports NOx concentration in PPM, including learned adjustments and offsets for improved accuracy.

NOx NTE Control Area Status

This PID reports on the vehicle’s operating status relative to NOx “Not-to-Exceed” (NTE) emissions control areas:

Inside/Outside NOx Control Area: Indicates if vehicle operation is within the NTE testing zone.
Inside/Outside Manufacturer Exception/’Carve-out’ Region: Indicates if operation is within a manufacturer-defined exemption area.
NTE Related Deficiency: Indicates if an NTE-related emissions issue is detected.

PM Sensor Bank 1 & 2

This PID reports status data for Particulate Matter (PM) sensors on banks 1 and 2:

Particulate Matter Sensor Active (yes/no): Sensor status.
Particulate Matter Sensor Regenerating (yes/no): Sensor regeneration status.
Particulate Matter Sensor Value (%): Soot loading level (0% = clean; 100% = regen needed).

Particulate Matter (PM) Sensor

This PID reports soot concentration in mg/m3 as measured by PM sensors on banks 1 and 2.

PM NTE Control Area Status

Similar to NOx NTE Control Area Status, this PID reports on the vehicle’s operating status relative to PM “Not-to-Exceed” (NTE) emissions control areas.

SCR Inducement System

This PID reports on the status of the Selective Catalytic Reduction (SCR) inducement system, which alerts drivers to SCR system issues and may implement functional restrictions.

SCR Inducement Status (On/Off): Indicates if inducement is active.
Reasons for Activation: Details the triggers for inducement (low reagent, incorrect reagent, etc.).
Historical Inducement Data: Indicates if inducement conditions occurred within previous 10,000 km intervals.

NOx Warning And Inducement System

This PID provides detailed information on NOx warning and inducement levels, categorized into three severity levels (Level 1-3).

Warning/Inducement Level Status (Inactive, Enabled but not active, Active, Not supported): Status for each severity level.
Historical Data: Reports total engine hours with incorrect reagent, consumption rate issues, interrupted dosing, EGR DTCs, and NOx control equipment DTCs.

Engine Run Time for AECD

This PID reports the total run time for each Emissions Increasing Auxiliary Emissions Control Device (AECD) that may temporarily disable emissions control components under specific conditions (permitted under regulations but must be justified).

AECD Timer Data (TIME1, TIME2): Reports engine run time during AECD activation, potentially differentiating between different levels of emissions control inhibition. Note: Timers cannot be reset.

Understanding OBD2 live data and these Parameter Identifiers is a powerful tool for anyone involved in vehicle maintenance and repair. By learning to interpret these values, you can gain a deeper understanding of your vehicle’s inner workings, diagnose problems more effectively, and contribute to keeping your car running smoothly and efficiently for years to come.