I found an old manual that had Engine Control System schematics for the '90 and '91 Integra, which is the OBD0 PR4 ECU.

Unfortunately, it didn't have pinouts for the ECU, but it did have wire colors and showed all the things the ECU is connected to. I went back to all my other OBD0 documentation for other cars and mapped the pin numbers to most of the wires using the colors and funtions.

There are two wires (RED/BLU & ORG/BLK) that go nowhere in the schematics.

I didn't bother to figure out the pin numbers for the Automatic Transmission signals, I'll let someone with AT interest do that. I was unable to find the OBD0 pins for the Data Link Connector (Lt BLU).

From what I have learned, it appears that only California Automatic Transmission Integras have an EGR valve. In that case pin A10 is the EGR Control (RED) and pin C8 is the valve lift sensor ((YEL).

In the case of all other Integras, it seems that pin A10 is the Pressure Regulator Cutoff Solenoid Valve (GRN/YEL) signal.

The Power Steering Pressure Switch (RED) is Pin C9. From what I have learned, it appears that only California Automatic Transmission Integras have an EGR valve. In that case pin A10 is the EGR Control (RED) and pin C8 is the valve lift sensor ((YEL). In the case of all other Integras, it seems that pin A10 is the Pressure Regulator Cutoff Solenoid Valve (GRN/YEL) signal.

The Power Steering Pressure Switch (RED) is Pin C9. From what I have learned, it appears that only California Automatic Transmission Integras have an EGR valve. In that case pin A10 is the EGR Control (RED) and pin C8 is the valve lift sensor ((YEL). In the case of all other Integras, it seems that pin A10 is the Pressure Regulator Cutoff Solenoid Valve (GRN/YEL) signal.

Find the OBD0 PR4 pinout and schematics here: http://forum.pgmfi.org/viewtopic.php?p=39477#39477

-- markolson - 25 May 2005