MIL Circuit Troubleshooting
2.3L Models:
MIL Circuit Troubleshooting
1. Connect an OBD II scan tool/Honda PGM Tester.
2. Turn the ignition switch ON (II), and read the OBD II scan tool/Honda PGM Tester.
Does the OBD II scan tool/Honda PGM Tester communicate with the ECM/PCM?
YES - Go to step 3.
NO - Go to troubleshooting "DLC Circuit Troubleshooting".
3. Check the OBD II scan tool/Honda PGM Tester for DTCs.
Are any DTCs indicated?
YES - Go to the DTC Troubleshooting index.
NO - Go to step 4.
4. Turn the ignition switch OFF.
5. Turn the ignition switch ON (II), and watch the Malfunction Indicator Lamp (MIL).
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 16. But if the MIL sometimes works normally, first check for these problems.
- An intermittent short in the wire between the ECM/PCM (A18) and the Data Link Connector (DLC).
- An intermittent open in the wire between the ECM/PCM (A21) and the DLC.
- An intermittent short in the wire between the ECM/PCM (A18) and the gauge assembly.
NO - If the ML 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 (7.5 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 ECM/PCM terminal A18.
- An intermittent open in the GRN/ORN wire between the ECM/PCM (A18) and the gauge assembly.
- An intermittent short in the wire between the ECM/PCM (C19) and the MAP sensor.
- An intermittent short in the wire between the ECM/PCM (C28) and the TP sensor, EGR valve position sensor, or Fuel Tank Pressure (FTP) Sensor.
6. Check the low oil pressure light.
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 (7.5 A) fuse in the driver's under-dash fuse/ relay box.
- A short or open in the wire between the No.9 BACK UP LIGHT, INSTRUMENT LIGHT (7.5 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 10.
8. Turn the ignition switch OFF, and connect ECM/PCM connector terminal A18 to body ground with a jumper wire.
9. Turn the ignition switch ON (II).
Is the MIL on?
YES - Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original ECM/PCM.
NO - Check for an open in the wires between the ECM/PCM (A18) and the gauge assembly. Also check for a blown MIL bulb.
10. Turn the ignition switch OFF, then disconnect ECM/PCM connector C (31P), and check for continuity between body ground and ECM/PCM connector terminals C19 and C28 individually.
Is there continuity?
YES - Go to step 11.
NO - Go to step 12.
11. Disconnect the 3P connector from each of these sensors, one at a time, and check for continuity between body ground and ECM/PCM connector terminal C19 and C28 individually.
- MAP Sensor
- EGR valve position sensor
- FTP sensor
- TP sensor
Is there continuity?
YES - Repair the short to body ground in the wire between the ECM/PCM (C19) and the MAP sensor, or the ECM/PCM (C28) and the TP sensor, EGR valve position sensor, or FTP sensor.
NO - Replace the sensor that made continuity to body ground go away when disconnected.
12. Disconnect the injectors and IAC valve connectors.
13. Turn the ignition switch ON (II), and measure voltage between body ground and ECM/PCM connector terminals B1 and B9 individually.
Is there battery voltage?
YES - Go to step 14.
NO - Check for these problems:
- An open in the wire(s) between the PGM-FI main relay and ECM/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 relay.
14. Reconnect the connectors to the sensors, then reconnect ECM/PCM connector C 131P).
15. Turn the ignition switch ON (II), and measure voltage between body ground and ECM/PCM connector terminals B2, B10, B20, and B22 individually.
Is there less than 1.0 V ?
YES - Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original ECM/PCM.
NO - Repair the open in the wire(s) that had more than 1.0 V between G101 and the ECM/PCM (B2, B10, B20, B22).
16. Turn the ignition switch OFF, then turn it back ON (II), and measure voltage between ECM/PCM connector terminal A10 and body ground.
Is there about 5V ?
YES - Go to step 17.
NO - Repair short in the wire between the DLC and the ECM/PCM (A10).
17. Turn the ignition switch OFF, disconnect ECM/PCM connector A (32P), then turn the ignition switch ON (II).
Does the MIL stay on?
YES - Repair short in the wire between the gauge assembly and the ECM/PCM (A18).
NO - Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original ECM/PCM.