A/T Model
MIL Circuit TroubleshootingA/T Model
1. Turn the ignition switch ON (II), and watch the Malfunction Indicator Lamp (MIL).
Does the MIL come on and stay on?
YES - If the MIL always come on and stays on, go to step 12. 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.
- An intermittent open in the wire between the PCM (A21) and the data link 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 2. 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 PCM terminal A18.
- An intermittent open in the GRN/ORN wire between the PCM (A18) and the gauge assembly.
- An intermittent short in the wire between the PCM (C19), the MAP sensor and the countershaft speed sensor.
- An intermittent short in the wire between the PCM (C28), the TP sensor, EGR valve position sensor, fuel tank pressure sensor and the mainshaft speed sensor.
2. Turn the ignition switch OFF and then ON (II) again.
Is the low oil pressure light on?
YES - Go to step 3.
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 No.9 BACK UP LIGHT, INSTRUMENT LIGHT (7.5 A) fuse and the gauge assembly.
3. Try to start the engine.
Does the engine start?
YES - Go to step 4.
NO - Go to step 6.
4. Turn the ignition switch OFF, and connect PCM connector terminal A18 and body ground with a jumper wire.
5. 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.
6. Turn the ignition switch OFF, then disconnect PCM connector C (31P) and check for continuity between body ground and PCM connector terminals C19 and C28 individually.
Is there continuity?
YES - Go to step 7.
NO - Go to step 8.
7. 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.
- MAP sensor
- EGR valve position sensor
- Fuel tank pressure sensor
- TP sensor
- Mainshaft speed sensor
- Countershaft speed sensor
Is there continuity?
YES - Repair the short to body ground in the wire between the PCM (19) and the MAP sensor, or countershaft speed sensor, or the PCM (C28) and the TP sensor, EGR valve position sensor, fuel tank pressure sensor or mainshaft speed sensor.
NO - Replace the sensor that made continuity to body ground go away when disconnected.
8. Disconnect the injectors and IAC valve connectors.
9. Turn the ignition switch ON (II), and measure voltage between body ground and PCM connector terminals B1 and B9 individually.
Is there battery voltage?
YES - Go to step 10.
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.
10. Reconnect the connectors to the sensors, then reconnect PCM connector C (31P).
11. 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) that had more than 1.0 V between G101 and the PCM (B2, B10, 620, or B22).
12. Turn the ignition switch OFF.
13. Connect an OBDII scan tool/Honda PGM Tester.
14. Turn the ignition switch ON (II), and read the OBDII scan tool/Honda PGM Tester.
Are any DTCs indicated?
YES - Go to step 15.
NO - Go to DLC Circuit Troubleshooting.
15. Turn the ignition switch OFF, then turn it back ON (II) and measure voltage between PCM connector terminal A10 and body ground.
Is there approx. 5 V?
YES - Go to step 16.
NO - Repair short in the wire between the DLC and the PCM (A10).
16. Turn the ignition switch OFF, disconnect PCM connector A (32P), and turn the ignition switch ON (II).
Is the MIL 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.