Experiencing OBD2 communication issues with your 1999 Dodge Ram 1500 can be a frustrating hurdle, especially when trying to diagnose other potential problems. This article delves into the common challenges faced when a ’99 Dodge Ram 1500 fails to communicate with an OBD2 scanner, offering a troubleshooting approach to pinpoint the root cause. We’ll explore potential culprits, from simple wiring issues to more complex PCM failures, providing insights to guide your diagnostic process.
Transmission Troubles and OBD2 Mystery
The owner of a 1999 Dodge Ram 1500 2500, equipped with an automatic transmission and boasting 370,000 miles, recently encountered a perplexing situation. After purchasing the truck with a faulty transmission and subsequently installing a remanufactured unit, initial driving revealed shifting problems – specifically, only 1st, 2nd, and 3rd gears were accessible, lacking overdrive (OD) and lockup.
Suspecting sensor discrepancies, the owner swapped the OD solenoid, pressure sensor, and wiring harness from the original transmission to the remanufactured one. This intervention successfully restored overdrive and lockup functionality. However, a new issue arose: the transmission now refused to downshift from 3rd gear without manual intervention.
Seeking professional diagnosis, the truck was taken to a transmission shop to read pressure values and identify the source of the shifting malfunction before resorting to parts replacement. It was during this diagnostic attempt that an entirely separate problem surfaced – the shop’s scanner failed to establish any communication with the OBD2 port.
Discovery of No OBD2 Communication
Despite the presence of power and ground at the OBD2 port, the diagnostic scanner remained unresponsive. Resistance checks were performed on the violet and black/white wires connecting the instrument cluster to the Powertrain Control Module (PCM), and these tests yielded satisfactory results, indicating wiring continuity.
This lack of OBD2 communication adds another layer of complexity to the initial transmission issue. The question arises: are these problems related, or are they independent faults? The owner suspects a potential PCM failure but is understandably hesitant to replace it without further diagnostic confirmation.
Troubleshooting Steps for OBD2 Communication Failure
When faced with a “99 Dodge Ram 1500 No Obd2 Communication” scenario, a systematic troubleshooting approach is crucial. Here are key areas to investigate:
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Verify OBD2 Port Power and Ground: As already checked, ensure that the OBD2 port is receiving power and ground. Use a multimeter to confirm 12V power on pin 16 and ground on pins 4 and 5.
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Inspect Wiring and Connectors: Thoroughly examine the wiring harness and connectors associated with the OBD2 port and PCM. Look for signs of damage, corrosion, or loose connections. Pay particular attention to the CAN bus wires (if applicable for this model year, though less common on ’99 Rams, but worth checking).
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Check Fuses: Inspect all relevant fuses related to the PCM and diagnostic system. A blown fuse can disrupt power supply and prevent OBD2 communication. Refer to your owner’s manual or a wiring diagram for fuse locations.
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PCM Power and Ground: Beyond the OBD2 port, verify that the PCM itself is receiving proper power and ground. Consult a wiring diagram for PCM power and ground pin locations and test with a multimeter.
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Instrument Cluster Issues: In some vehicles, the instrument cluster can be part of the communication pathway. While wiring to the cluster was checked, ensure the cluster itself is functioning correctly and not causing a communication breakdown.
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PCM Fault: While it’s a more costly component, a faulty PCM is a potential cause of no OBD2 communication. If all other troubleshooting steps are exhausted, PCM failure becomes a stronger possibility. However, consider professional PCM testing before replacement.
Could the PCM Be the Culprit?
Given the troubleshooting steps taken, a faulty PCM remains a plausible explanation for the “99 dodge ram 1500 no obd2 communication” issue. The fact that basic wiring and power to the port are confirmed good points towards a deeper internal problem within the PCM itself.
However, before concluding PCM replacement is necessary, further in-depth diagnostics are advisable. Consulting with a qualified mechanic or a specialist in automotive electronics can provide access to advanced diagnostic tools and expertise to definitively pinpoint the cause. They may be able to perform PCM testing or use more sophisticated scanners to attempt communication on different protocols.
Seeking Expert Insight
Diagnosing OBD2 communication problems, especially in conjunction with other vehicle issues, can be complex. If you are experiencing “99 dodge ram 1500 no OBD2 communication,” systematically working through the troubleshooting steps outlined above will help narrow down the potential causes. Don’t hesitate to seek expert advice from experienced mechanics or diagnostic specialists to ensure accurate diagnosis and effective resolution.
