Understanding your Honda Engine Control Unit (ECU) is crucial for diagnostics, upgrades, and ensuring your vehicle runs smoothly. Whether you’re dealing with an older OBD1 system or a more modern OBD2 setup, identifying your ECU correctly is the first step. While this article won’t provide a direct “Obd1 To Obd2 Distributor Wiring Diagram”, it will equip you with the knowledge to accurately identify your ECU type and generation, which is essential information when considering wiring diagrams or any ECU-related modifications, including potential OBD1 to OBD2 conversions involving distributor wiring.
Locating Your Honda ECU
Before diving into part numbers and diagrams, you need to find your ECU. The location varies depending on your Honda model and year:
- Early Models (Up to 1991): Check under a metal plate in the passenger’s side footwell.
- Mid-1990s Models (1992-1999): Look in the passenger’s footwell, behind a plastic panel.
- Later Models (2000+): For some models, the ECU is located by the driver’s footwell, again behind a plastic panel.
Once you’ve located the ECU, disconnect the three wiring connectors by pressing the plastic clips. Carefully remove the ECU unit.
Alt text: Location of a Honda ECU in the passenger footwell of a vehicle, showing the plastic panel that may need to be removed for access.
ECU Part Numbers: Your Key to Identification
The most reliable way to identify your Honda ECU is by its part number. This number is printed on the side of the ECU casing and also on the connector inside the ECU itself. A typical Honda ECU part number looks like this: 37820-P72-A01.
Let’s break down the components of this part number:
- 37820: This is Honda’s standard prefix for ECUs and remains consistent across all models.
- P72: These three characters are crucial. They loosely relate to the car model and engine type. For example, “P72” is commonly associated with Integra GSR models. Different ECU generations can use the same middle characters, so context is important. A “P72” OBD1 ECU is different from a “P72” OBD2 ECU.
- A01: These last three characters indicate the ECU’s revision or variant. The first letter often denotes the region (e.g., “A” for US, “G” for European, “J” for Japanese). The second digit typically represents the transmission type (“0” for manual, “5” for automatic). The last digit is a version number.
Alt text: Close-up view highlighting the location of the part number on the side of a Honda Engine Control Unit (ECU).
Decoding Common Honda ECU Part Numbers
Here’s a list of common Honda ECU codes to help you identify your ECU type and potentially its OBD generation. This list is not exhaustive, but covers many popular models:
OBD1 ECUs (Typically 1988-1995):
- PG7: 86-89 Integra (86-87 vacuum advance, 88-89 electronic advance)
- PM5: 88-91 Civic/CRX DX
- PM6: 88-91 Civic/CRX SOHC Si
- PM7: 89-91 DOHC ZC (JDM ‘EF’ ECU)
- PM8: 88-91 CRX HF
- PR2: 89-91 ZC (Euro)
- PR3: 89-91 JDM B16A EF8/9
- PR3 -J00 or J51: 92 JDM Integra B16A EF8/9
- PW0: 89-91 JDM B16A EF8/9 DA6-XSi
- PR4: 90-91 Integra LS/GS
- PS9: 88-91 4 door Civic EX Auto
- P05: 92-95 OBD-1 Civic CX
- P06: 92-95 OBD-1 Civic DX
- P07: 92-95 OBD-1 Civic VX
- P08: 92-95 OBD-1 Civic D15 JDM
- P0A: 94-95 OBD-1 Accord EX
- P13: 93-95 OBD-1 Prelude Vtec
- P14: 93-95 OBD-1 Prelude Si (non Vtec)
- P27: 92-95 OBD-1 EG JDM Civic 1600 sohc
- P28: 92-95 OBD-1 Civic Si/Ex
- P30: 92-95 OBD-1 DelSol DOHC Vtec Si/EG SiR
- P61: 92-93 OBD-1 Integra GSR
- P72: 94-95 OBD-1 Integra GSR
- P74/75: 92-95 OBD-1 Integra LS/GS
OBD2 ECUs (Typically 1996-2001+):
- P54-G31: 1997 Honda Accord 1.8 LS
- P72: 96-00 OBD-2 Integra GSR
- P73: 96-00 OBD-2 Integra Type-R (JDM & USDM)
- P75: 96-00 OBD-2 Integra LS/GS
- P2N: 96+ OBD-2 Civic HX Coupe
- P2P: 96+ OBD-2 Civic EX Coupe
- P2E: 96+ OBD-2 Civic DX Coupe
- P2M: 96+ OBD-2 NZ Civic SOHC VTEC
- P2T: 99+ OBD-? Civic Si Coupe
- P5P: 97-00 OBD-2 Prelude Type-S (JDM ECU)
- PBA: 97+ US Acura 1.6EL
- PCT: 98+ JDM ITR / CTR
- PCX: 99+ OBD-? S2000 ECU
Important Notes on OBD1 vs OBD2 and Distributor Wiring:
- OBD Generation Matters: OBD1 and OBD2 systems are fundamentally different in their diagnostic protocols and wiring. While this article doesn’t provide distributor wiring diagrams, understanding whether you have an OBD1 or OBD2 ECU is critical because the distributor wiring and ECU pinouts will be different between the two systems.
- “OBD1 to OBD2 Distributor Wiring Diagram” Context: Users searching for “OBD1 to OBD2 distributor wiring diagram” are often considering engine swaps or ECU upgrades and need to adapt the older OBD1 distributor wiring to a newer OBD2 ECU or vice-versa. Accurate ECU identification is the first step in finding the correct wiring diagrams and ensuring compatibility.
- ROM Numbers (Further Identification): For even more specific identification, Honda ECUs also have a software ROM revision number inside the ECU, usually a two or three-digit code stamped on the 28-pin ROM chip or main processor. Accord and Prelude ECUs might use a letter and number code. This level of detail is generally not necessary for basic identification related to OBD1/OBD2 and distributor wiring but can be helpful for advanced tuning or troubleshooting.
Conclusion: Identifying Your ECU for Wiring and Beyond
While a direct “OBD1 to OBD2 distributor wiring diagram” is highly specific to the exact vehicles and ECUs involved in a conversion, this guide provides the essential first step: accurately identifying your Honda ECU. By locating your ECU and deciphering its part number, you can determine its OBD generation (OBD1 or OBD2) and find the correct wiring diagrams and information needed for your specific project, whether it involves distributor wiring, engine swaps, or ECU upgrades. Always consult official repair manuals and wiring diagrams specific to your vehicle and ECU part numbers for any wiring modifications.
