OBD1 ECU (P75) and OBD1 distributor with OBD0-to-OBD1 conversion harness

OBD1 ECU (P75) and OBD1 distributor with OBD0-to-OBD1 conversion harness

Electrical Engine management (OBD0 to OBD1 conversion) Verified Modification Required

Compatibility Overview

Source Vehicle

Integra VTi-R

Generation: DC2 (OBD1 era)

Target Vehicle

CR-X SiR

Generation: EF8 (OBD0; procedure applies to any OBD0 Civic/CR-X)

Years: 1989-1991

Installation Difficulty

Easy Basic tools
Moderate Some experience
Difficult Skilled work
Expert Professional

Reference

B16A specs → B18C specs → F20C specs → H22A specs → K20A specs → K24A specs → C20AT specs → D17A specs → LEB-H5 specs → R20A6 specs → R18Z6 specs → B18A specs → D15A1 specs → EW5 specs → J25A specs → B20B specs → K20Z2 specs → B18C-00-Spec-R specs → B18B specs → B18C-96-Spec-R specs → B18C-98-Spec-R specs → B18C-SiR-G specs → K20A-RAA specs → K24A-RBB specs → C32B specs → C30A specs → L15ZF specs → L15BU specs → L13B specs → ZC SOHC specs → ZC SOHC Carb specs → ZC DOHC Gen2 specs → ZC SOHC VTEC specs → B16A SiRII specs → F18B specs → F20B-CF4 specs → F20B specs → ZC DOHC specs → P75 Cylinder Head → PLE Cylinder Head → PR3 Cylinder Head → RNE ECU →
Documented conversion of an OBD0 EF8 CR-X to OBD1 using a P75 ECU and an OBD1 distributor from an Integra VTi-R; a DC2 distributor bolted up and worked well. The car ran Crome with a stock 203 ROM for an OBD1 JDM B16A and started on the first attempt. The original single-wire O2 sensor works fine with the heater circuits disabled in the ROM. With this harness the blue 2-pin connector formerly used for setting timing (under the LH dash near the heater blower on EF8/EF9) becomes the SCS connector for OBD1 diagnostics and base-timing adjustment. Base ignition timing must be set with a timing light after conversion. A follow-up member completed the same conversion successfully with the car starting first go.
The OBD1 ECU connects through an OBD0-to-OBD1 jumper harness (Boomslang Fabrications harness used) - no cutting of the car loom for the ECU itself. The harness sub-harness wires must be joined to the car: on an already-VTEC OBD0 car, the green (VTEC solenoid) wire goes to car-loom pin A8 (green/white) and the white (O2 signal) wire to C16 (white with silver dots), with optional VTP/heated-O2 wiring; on a non-VTEC chassis receiving a VTEC engine, the green, pink (IAB), red (knock) and four O2 wires are run directly to the engine-bay sensors, with the IAB solenoid's yellow/black wire fed from a switched 12 V source (available at the EACV). The distributor swap requires de-pinning the OBD0 connectors from the old distributor and transferring the OBD1 distributor wires into them per a specific pin map (ICM pin 7 to pin 7; OBD1 pins 1-6 to OBD0 pins 4, 3, 6, 5, 2, 1 respectively); the spade terminals on the power/tacho wires may need to be cut from the OBD0 distributor and soldered onto the OBD1 wires. Unused inputs (knock, ELD, O2 heater, VTP) are disabled in the ROM (Crome).

Important Caveats

  • • Only works on OBD0 cars with non-vacuum-advance distributors; pre-OBD0 cars with vacuum-advance distributors share the same ECU connectors but are wired differently.
  • • If using a chipped P28 ECU, disable the knock sensor in Crome - the P28 does not use one.
  • • Mark the ICM wire (pin 7) before de-pinning the distributor connector so it is not confused with the other white wire, and note the orientation of the blue and black/yellow wires on the power/tacho connector.
  • • Get the firing order right (1-3-4-2) when refitting the leads.

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Community Verification

1
user verified this swap
By ECU-MAN via OzHonda
Added 7 hours ago

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