Civic2Fast

I've been searching and read many threads on troubleshooting code 43. I've read everything from change 02 sensor, to fuel pump, to fuel pressure. I will be posting the step-by-step procedure based on an OBD1 1995 Civic Coupe

Key:
MIL = Malfunction Indicator Lamp (CEL)
H02S = Heated Oxygen Sensor
ECM = Engine control module
VDC = Volts (direct currect)

1. - The MIL has been reported on.
- With the service check connector jumped, code 43 is indicated.

2. - Is the code 43 accompanied by the MIL and poor driveability? If yes, then troubleshoot Fuel Supply system (not covered in this thread) If no, continue to step three.

3. -Do the ECM Reset procedure

4. -Warm up engine to normal operating temperature (the radiator fan comes on)

5. -Connect the jumper wire to the service check connector.

6. -Hold engine at 3,000 RPM for two minutes. (A/T: Transmission in neutral or park position)

7. -Is the MIL on and does it indicate code 43? If yes, continue to step 8. If no, you have an intermittent failure, the system is OK at this time (test drive may be necessary) Check for poor connections or loose wires at C213 (connector located at the right shock tower), C111 (the connector from the H02S to the ECM)

8. - This step is also starts the beginning of a MIL code 1 (heated oxygen sensor).

FROM HERE FORWARD YOU WILL NEED A DIGITAL MULTIMETER SET AT THE 2V DC RANGE.

9. -Turn the ignition switch to the OFF position and wait at least 2 minutes

10. -Install a jumper wire from pin A6 to A26 (wish I could post an ECU pinout, but I don't have picture posting abilities at the moment)

11. -turn the ignition switch to ON

12. -Measure the voltage between D14 (+) terminal and A26 (-) terminal as soon as the ignition switch is turned on. Voltage should start at .4-.5 VDC and decrease to less than .1 VDC in less than 2 minutes.

13. -Is there .1 VDC or less when the ignition switch is first turned on? If yes, go to step 16. If no, continue to step 14.

14. -Disconnect the 4P connector from the H02S

15. -Measure voltage at the engine wire harness side of the H02S connector between the green/white wire (-) and the white wire (+). Is there more than .1 VDC? If yes, then replace H02S. If no, check for an open in the white wire between ECM (D14) and H02S. If that wire checks ok, repair is necessary in open for GRN/WHT wire between ECM (D22) and H02S.

16. -Disconnect the 4P connector from the H02S.

17. -Measure voltage between D14 (+) and A26 (-) terminal.

18. -Is there more than .1 VDC? If yes, then replace H02S. If no, continue to step 19.

19. -Turn the ignition switch to OFF.

20. -Disconnect the "D" connector from the main wire harness.

21. -Turn the ignition switch to ON

22. -Measure voltage between D14 (+) terminal and A26 (-) terminal. is there more than .1 VDC? If yes, repair the short in the white wire between ECM (D14) and H02S. If no, substitute a known-good ECM and recheck. If symptom/indication goes away, replace your ECM.


I typed this really fast and if anyone has anything to add, please do.

Thanks!!!