Malfunction Indicator Lamp: Testing and Inspection
MIL Circuit Troubleshooting1. Connect the HDS.
2. Turn the ignition switch ON (II), and read the HDS.
Does the HDS communicate with the PCM?
YES - Go to step 3.
NO - Go to troubleshooting "DLC Circuit Troubleshooting".
3. Check for DTCs with the HDS.
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 (II).
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 (B54) and the data link connector (DLC) connector.
- An intermittent short in the wire between the PCM (B5) 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 No.46 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 B5.
- An intermittent open in the GRN/ORN wire between the PCM (B5) and the gauge assembly.
- An intermittent short in the wire between the PCM (A7) and the manifold absolute pressure (MAP) sensor, the output shaft (countershaft) speed sensor.
- An intermittent short in the wire between the PCM (A27) and the exhaust gas recirculation (EGR) valve position sensor, the input shaft (mainshaft) speed sensor, or the intake manifold runner control actuator.
- An intermittent short in the wire between the PCM (B43) and the APP sensor.
- An intermittent short in the wire between the PCM (B29) and the APP sensor.
- An intermittent short in the wire between the PCM (B46) and 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 12.
8. Turn the ignition switch OFF.
9. Disconnect PCM connector B (56P).
10. Connect PCM connector terminal B5 to body ground with a jumper wire.
11. 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 wire between the PCM (B5) and the gauge assembly. Also check for a blown MIL bulb.
12. Turn the ignition switch OFF.
13. Inspect the No.46 ACGS (15 A) fuse in the under-hood 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.46 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, CKP sensors or CMP sensor.
14. Inspect the No.1 FUEL PUMP (15 A) fuse in the under-dash fuse/relay box.
Is the fuse OK?
YES - Go to step 15.
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.
15. Disconnect PCM connectors A (73P) and B (56P).
16. Check for continuity between body ground and PCM connector terminals A7, A27, B29, B43, and B46 individually.
Is there continuity?
YES - Go to step 17.
NO - Go to step 18.
17. Disconnect the connector from each of these sensors, one at a time, and check for continuity between body ground and PCM connector terminal A7, A27, B29, B43, and B46 individually.
- Manifold absolute pressure (MAP) sensor
- Output shaft (countershaft) speed sensor
- Exhaust gas recirculation (EGR) valve position sensor
- Accelerator pedal position (APP) sensor
- Fuel tank pressure (FTP) sensor
- Input shaft (mainshaft) speed sensor
- IMRC actuator
Is there continuity?
YES - Repair short to ground in the wire between PCM and the following sensors.
- MAP sensor (A7)
- APP sensor (sensor 1) (B43)
- Output shaft (countershaft) speed sensor (A7)
- Input shaft (mainshaft) speed sensor (A27)
- EGR valve position sensor (A27)
- APP sensor (sensor 2) (B29)
- FTP sensor (B46)
- IMRC actuator
NO - Replace the sensor that made continuity to body ground go away when disconnected.
18. Reconnect the PCM connector B (56P).
19. Turn the ignition switch ON (II).
20. Measure voltage between body ground and the PCM connector terminal A18.
Is there battery voltage?
YES - Go to step 21.
NO - Check for these problems:
- An open in the wire(s) between the PGM-FI main relay and PCM connector terminals A18.
- Poor connections at the PGM-FI main relay.
- A faulty PGM-FI main relay. If necessary, repair or replace the part.
21. Check for continuity between PCM connector terminals A39, A40, and A73.
Is there continuity?
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 PCM (A39, A40, A73,) and body ground (G101).
22. Reconnect the PCM connectors.
23. Turn the ignition switch OFF, then turn it back ON (II) and measure voltage between DLC connector terminal No.9 and body ground.
Is there about 5 V (or battery voltage)?
YES - Go to step 27.
NO - Go to step 24.
24. Turn the ignition switch OFF.
25. Disconnect PCM connector B (56P).
26. Check for continuity between PCM connector terminal B54 and body ground.
Is there continuity?
YES - Repair short in the wire between the data link connector and the PCM (B54).
NO - Substitute a known-good PCM and recheck. If symptom/indication goes away, replace the original PCM.
27. Turn the ignition switch OFF.
28. Disconnect PCM connector A (32P).
29. Turn the ignition switch ON (II).
Does the MIL stay on?
YES - Repair short in the wire between the gauge assembly and the PCM (B5).
NO - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.