Malfunction Indicator Lamp: Testing and Inspection
MIL Circuit Troubleshooting1. Connect a scan tool/Honda PGM Tester.
2. Turn the ignition switch ON (II), and read the scan tool/Honda PGM Tester.
Does the scan tool/Honda PGM Tester communicate with the PCM?
YES - Go to step 3.
NO - Go to troubleshooting "DLC Circuit Troubleshooting".
3. Check for DTCs with the scan tool/Honda PGM Tester.
Are any DTCs indicated?
YES - Go to the DTC Troubleshooting Index Diagnostic Trouble Code Descriptions.
NO - Go to step 4,
4. Turn the ignition switch OFF.
5. Turn the ignition switch ON.
Does the MIL come on and stay on for more than 20 seconds after turning the ignition switch ON (II)?
YES - If the MIL always comes on and stays on, go to step 22. But if the MIL sometimes works normally, first check for these problems.
- An intermittent short in the wire between the PCM (A10) and the Data Link Connector (DLC) connector.
- An intermittent short in the wire between the PCM (A18) and the gauge assembly.
NO - If the MIL is always off, go to step 6. But if the MIL sometimes works normally, first check for these problems.
- A loose No.9 BACK UP LIGHT, INSTRUMENT LIGHT (10 A) fuse in the driver's under-dash fuse/relay box.
- A loose ACG S (15 A) fuse in the under-hood fuse/relay box.
- A loose No.1 FUEL PUMP (15 A) fuse in the driver's under-dash fuse/relay box.
- A poor connection at PCM terminal A18.
- An intermittent open in the PUR wire between the PCM (A18) and the gauge assembly.
- An intermittent short in the wire between the PCM (C19) and the manifold absolute pressure (MAP) sensor, the countershaft speed sensor.
- An intermittent short in the wire between the PCM (C28) and the throttle position (TP) sensor, Exhaust Gas Recirculation (EGR) valve position sensor, the mainshaft speed sensor, or the fuel tank pressure (FTP) sensor.
6. Turn the ignition switch OFF and then ON (II) again.
Is the low oil pressure light on?
YES - Go to step 7.
NO - Check for these problems:
- A blown No.9 BACK UP LIGHT, INSTRUMENT LIGHT (10 A) fuse in the driver's under-dash fuse/relay box.
- A short or open in the wire between No.9 BACK UP LIGHT, INSTRUMENT LIGHT (10 A) fuse and the gauge assembly.
7. Try to start the engine.
Does the engine start?
YES - Go to step 8.
NO - Go to step 11.
8. Turn the ignition switch OFF.
9. Connect PCM connector terminal A18 to body ground with a jumper wire.
10. Turn the ignition switch ON (II).
Is the MIL on?
YES - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.
NO - Check for an open in the wires between the PCM (A18) and the gauge assembly. Also check for a blown MIL bulb.
11. Turn the ignition switch OFF.
12. Inspect the ACGS (15 A) fuse in the under-hood fuse/relay box.
Is the fuse OK?
YES - Go to step 13.
NO - Check for these problems:
- A short in the wire between the ACGS (15 A) fuse and the PGM-FI main relay.
- A short in the wire between the PGM-FI main relay and the PCM, injectors, or IAC valve.
13. Inspect the No.1 FUEL PUMP (15 A) fuse in the under-dash fuse/relay box.
Is the fuse OK?
YES - Go to step 14.
NO - Check for these problems:
- A short in the wire between the No.1 FUEL PUMP (15 A) fuse and the PGM-FI main relay.
- A short in the wire between the PGM-FI main relay and the fuel pump.
- A faulty PGM-FI main relay or a faulty fuel pump.
14. Disconnect PCM connector C (31P).
15. Check for continuity between body ground and PCM connector terminals C19 and C28 individually.
Is there continuity?
YES - Go to step 16.
NO - Go to step 17.
16. Disconnect the 3P connector from each of these sensors, one at a time, and check for continuity between body ground and PCM connector terminal C19 and C28 individually.
- Manifold Absolute Pressure (MAP) sensor
- Countershaft speed sensor
- Exhaust Gas Recirculation (EGR) valve position sensor
- Throttle Position (TP) sensor
- Fuel Tank Pressure (FTP) sensor
- Mainshaft speed sensor
Is there continuity?
YES - Repair short to body ground in the wire between PCM (C19) and the MAP sensor or countershaft speed sensor, or PCM (C28) and the TP sensor, EGR valve position sensor, mainshaft speed sensor or FTP sensor.
NO - Replace the sensor that made continuity to body ground go away when disconnected.
17. Disconnect the injectors and IAC valve connectors.
18. Turn the ignition switch ON (II).
19. Measure voltage between body ground and the PCM connector terminals B1 and B9 individually.
Is there battery voltage?
YES - Go to step 20.
NO - Check for these problems:
- An open in the wire(s) between the PGM-FI main relay and PCM connector terminals B1 and B9.
- Poor connections at the PGM-FI main relay.
- A faulty PGM-FI main relay. If necessary, repair or replace the part.
20. Reconnect the connectors to the sensors, then reconnect PCM connector C (31P).
21. Turn the ignition switch ON (II), and measure voltage between body ground and PCM connector terminals B2, B10, B20 and B22 individually.
Is there less than 1.0 V ?
YES - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.
NO - Repair the open in the wire(s) between that had more than 1.0 V between G1O1 and the PCM (B2, B1O, B20, B22).
22. Turn the ignition switch OFF, then turn it back ON (II) and measure voltage between PCM connector terminal A10 and body ground.
Is there about 5 V (or battery voltage)?
YES - Go to step 26.
NO - Go to step 23.
23. Turn the ignition switch OFF.
24. Disconnect PCM connector A (32P).
25. Check for continuity between PCM connector terminal A10 and body ground.
Is there continuity?
YES - Repair short in the wire between the data link connector and the PCM (A10).
NO - Substitute a known-good PCM and recheck. If symptom/indication goes away, replace the original PCM.
26. Turn the ignition switch OFF.
27. Disconnect PCM connector A (32P).
28. Turn the ignition switch ON (II).
Does the MIL stay on?
YES - Repair short in the wire between the gauge assembly and the PCM (A18).
NO - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.