MIL Circuit Troubleshooting (Except KH)

1.Connect the HDS/scan tool.

2.Turn the ignition switch ON (II) and read the HDS/scan tool.

Does the the HDS/scan tool communicate with the ECM/PCM?


YES - Go to 3.


NO - Go to troubleshooting ‘‘DLC circuit''.


3.Check the HDS/scan tool for DTCs.

Are any DTCs indicated?


YES - Go to the DTC Troubleshooting.


NO - Go to 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?


YES - If the MIL always come on and stays on, go to 67. But if the MIL sometimes works normally, first check for these problems.

  • An intermittent short in the wire between the  ECM/ PCM (E29) and the  Data Link Connector (DLC).
  • An intermittent short in the wire between the  ECM/ PCM (E31) and the gauge assembly.

NO - If the MIL is always off, go to 6. But if the MIL sometimes works normally, first check for these problems.

  • A loose No. 10 METER (7.5 A) fuse in the under-dash fuse/relay box.
  • A loose No. 20 IG (50 A) fuse in the under-hood fuse/relay box.
  • A loose No. 2 ENG (30 A) fuse in the under-hood fuse/relay box.
  • A loose IGP (15 A) fuse in the under-hood subfuse/relay box A.
  • A loose No. 17 FUEL PUMP (15 A) fuse in the under-dash fuse/relay box.
  • A poor connection at  ECM/ PCM terminal E31.
  • An intermittent open in the GRN/WHT wire between the  ECM/ PCM (E31) and the gauge assembly.
  • An intermittent short in the wire between the  ECM/ PCM (A21) and the  manifold absolute pressure (MAP) sensor, countershaft speed sensor (KP, KT, KU, KZ models (A/T)).
  • An intermittent short in the wire between the  ECM/ PCM (A20) and the  throttle position (TP) sensor, mainshaft speed sensor (KP, KT, KU, KZ models (A/T)).
  • An intermittent short in the wire between the  ECM/ PCM (E5) and the idle mixture adjuster (IMA) (without TWC).

6.Turn the ignition switch OFF.

7.Turn the ignition switch ON (II).

Is the low oil pressure light on?


YES - Go to 10.


NO - Go to 8.


8.Inspect the No. 10 METER (7.5 A) fuse in the under-dash fuse/relay box.

Is the fuse OK?


YES - Go to 9.


NO - Repair short in the wire between No. 10 METER (7.5 A) fuse and the gauge assembly. Also replace the No. 10 METER (7.5 A) fuse.n


9.Inspect the No. 20 IG1 (50 A) fuse in the under-hood fuse/relay box.

Is the fuse OK?


YES - Repair open in the wire between the No. 20 IG (50 A) fuse and the gauge assembly. If the wires are OK, test the ignition switch.n


NO - Repair short in the wire between the No. 20 IG (50 A) fuse and the under-hood fuse/relay box. Also replace the No. 20 IG (50 A) fuse.n


10.Try to start the engine.

Does the engine start?


YES - Go to 11.


NO - Go to 13.

11.Turn the ignition switch OFF. Connect ECM/PCM connector terminal E31 to body ground with a jumper wire.

 

12.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.n


NO - Check for an open in the wires between the  ECM/ PCM (E31) and the gauge assembly. Also check for a blown MIL bulb. If the wires and the bulb are OK, replace the gauge assembly.n


13.Turn the ignition switch OFF.

14.Remove and inspect the IGP (15 A) fuse in the under-hood subfuse/relay box A.

Is the fuse OK?


YES - Go to 20.


NO - Go to 15.

15.Remove the glove box, PGM-FI main relay 1 (A).

 

16.Check for continuity between body ground and PGM-FI main relay 1 4P connector terminals No. 2 and No. 4 individually.

 

Is there continuity?


YES -

  • Repair short in the wire between the IGP ( 15 A) fuse and the  PGM-FI main relay 1. Also replace the IGP (15 A) fuse.n
  • Repair short in the wire between the IGP (15 A) fuse and the No. 2 ENG (30 A) fuse. Also replace the No. 2 ENG (30 A) fuse.n

NO - Go to 17.

17.Disconnect each of the component or the connector sensors below, one at a time, and check for continuity between the PGM-FI main relay 1 4P connector terminal No. 1 and body ground.

  • PGM-FI main relay 2
  • ECM/PCM connector A (31P)
  • Each injector 2P connector
  • Idle air control (IAC) valve 3P connector
  • Top dead center (TDC) sensor 2P connector
  • Crankshaft position (CKP) sensor 3P connector

 

Is there continuity?


YES - Go to 18.


NO - Replace the item that made continuity to body ground go away when disconnected. If the item is the ECM/PCM, substitute a known-good ECM/PCM and recheck.
If the symptom/indication goes away, replace the original  ECM/ PCM.
Also replace the IGP (15 A) fuse or the No. 2 ENG (30 A) fuse.n


18.Disconnected the connectors of all following items.

  • PGM-FI main relay 2
  • ECM/PCM connector A (31P)
  • Injectors
  • Idle air control (IAC) valve
  • Top dead center (TDC) sensor
  • Crankshaft position (CKP) sensor

19.Check for continuity between PGM-FI main relay 1 4P connector terminals No. 1 and body ground.

 

Is there continuity?


YES - Repair short in the wire between  PGM-FI main relay 1 and each item. Also replace the IGP (15 A) fuse or the No. 2 ENG (30 A) fuse.n


NO - Replace the PGM-FI main relay 1. Also replace the IGP (15 A) fuse or the No. 2 ENG (30 A) fuse.n


20.Remove and inspect the No. 17 FUEL PUMP (15 A) fuse in the under-dash fuse/relay box.

Is the fuse OK?


YES - Go to 30.


NO - Go to 21.


21.Disconnect ECM/PCM connector E (31P).

22.Check for continuity between ECM/PCM connector terminal E9 and body ground.

 

Is there continuity?


YES - Go to 23.


NO - Replace the No. 17 FUEL PUMP (15 A) fuse, and substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original  ECM/ PCM.n


23.Remove the glove box, PGM-FI main relay 2 (A).

 

24.Check for continuity between ECM/PCM connector terminal E9 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the No. 17 FUEL PUMP (15 A) fuse and the  ECM/ PCM (E9), or the No. 17 FUEL PUMP (15 A) fuse and the  PGM-FI main relay 2. Also replace the No. 17 FUEL PUMP (15 A) fuse.n


NO - Go to 25.


25.Fold the rear seats forward, and pull back the carpet to expose the access panel.

26.Remove the access panel from the floor. Disconnect the fuel pump 5P connector.

27.Check for continuity between fuel pump 5P connector terminal No. 5 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the fuel pump and the  PGM-FI main relay 2. Also replace the No. 17 FUEL PUMP (15 A) fuse.n


NO - Go to 28.


28.Reinstall PGM-FI main relay 2 (A).

 

29.Check for continuity between fuel pump 5P connector terminal No. 5 and body ground.

 

Is there continuity?


YES - Replace  PGM-FI main relay 2. Also replace the No. 17 FUEL PUMP (15 A) fuse.n


NO - Check the fuel pump, and replace it if necessary. Also replace the No. 17 FUEL PUMP (15 A) fuse.n


30.Disconnect ECM/PCM connector E (31P).

31.Turn the ignition switch ON (II).

32.Measure voltage between ECM/PCM connector terminals E9 and body ground.

 

Is there battery voltage?


YES - Go to 33.


NO - Repair open in the wire between the No. 17 FUEL PUMP (15 A) fuse and the  ECM/ PCM (E9).n

33.Measure voltage between ECM/PCM connector terminal E7 and body ground.

 

Is there battery voltage?


YES - Go to 37.


NO - Go to 34.


34.Turn the ignition switch OFF and remove PGM-FI main relay 1 (A).

 

35.Measure voltage between PGM-FI main relay 1 4P connector terminal No. 4 and body ground.

 

Is there battery voltage?


YES - Go to 36.


NO -

  • Repair open in the wire between the IGP (15 A) fuse and  PGM-FI main relay 1.n
  • Repair open in the wire between the IGP (15 A) fuse and the No. 2 ENG (30 A) fuse.n

36.Check for continuity between PGM-FI main relay 1 4P connector terminal No. 3 and ECM/PCM connector terminal E7.

 

Is there continuity?


YES - Test PGM-FI main relay 1. If the relay is OK, substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original  ECM/ PCM.n


NO - Repair open in the wire between  PGM-FI main relay 1 and the  ECM/ PCM (E7).n

37.Reconnect ECM/PCM connector E (31P).

38.Turn the ignition switch ON (II).

39.Measure voltage between body ground and ECM/PCM connector terminals A2 and A3 individually.

 

Is there battery voltage?


YES - Go to 45.


NO - Go to 40.


40.Turn the ignition switch OFF and remove PGM-FI main relay 1 (A).

 

41.Turn the ignition switch ON (II).

42.Measure voltage between PGM-FI main relay 1 4P connector terminal No. 2 and body ground.

 

Is there battery voltage?


YES - Go to 43.


NO -

  • Repair open in the wire between the IGP (15 A) fuse and  PGM-FI main relay 1.n
  • Repair open in the wire between the IGP (15 A) fuse and the No. 2 ENG (30 A) fuse.n

43.Turn the ignition switch OFF.

44.Check for continuity between PGM-FI main relay 1 4P connector terminal No. 1 and ECM/PCM connector terminals A2 and A3 individually.

 

Is there continuity?


YES - Replace the  PGM-FI main relay 1.n


NO - Repair open in the wire between  PGM-FI main relay 1 and the  ECM/ PCM (A2, A3).n

45.Measure voltage between body ground and ECM/PCM connector terminals A4, A5, A23 and A24 individually.

 

Is there less than 0.2 V?


YES - Repair open in the wire(s) that had more than 0.2 V between  G101 and  ECM/ PCM (A4, A5, A23, A24).n


NO - Go to 46.


46.Measure voltage between body ground and ECM/PCM connector terminals A21.

 

Is there about 5 V?


YES - Go to 53.


NO - Go to 47.

47.Turn the ignition switch OFF.

48.Disconnect the 3P connector from each of these sensors, one at a time, and measure voltage between body ground and ECM/PCM connector terminal A21 with the ignition switch ON (II).

  • Manifold absolute pressure (MAP) sensor
  • Countershaft speed sensor (KP, KT, KU, KZ models (A/T))

 

Is there about 5 V?


YES - Replace the sensor that restored 5 V when disconnected.n


NO - Go to 49.


49.Turn the ignition switch OFF.

50.Disconnect the 3P connectors from the following sensors.

  • Manifold absolute pressure (MAP) sensor
  • Countershaft speed sensor (KP, KT, KU, KZ models (A/T))

51.Disconnect ECM/PCM connector A (31P).

52.Check for continuity between ECM/PCM connector terminal A21 and body ground.

 

Is there continuity?


YES - Repair short in the wire between  ECM/ PCM (A21) and the  MAP sensor, countershaft speed sensor (KP, KT, KU, KZ models (A/T)).n


NO - Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original  ECM/ PCM.n


53.Measure voltage between body ground and ECM/PCM connector terminals A20.

 

Is there about 5 V?


YES - Go to 60.


NO - Go to 54.

54.Turn the ignition switch OFF.

55.Disconnect the 3P connector from each of these sensors, one at a time, and measure voltage between body ground and ECM/PCM connector terminal A20 with the ignition switch ON (II).

  • Throttle position (TP) sensor
  • Mainshaft speed sensor (KP, KT, KU, KZ models (A/T))

 

Is there about 5 V?


YES - Replace the sensor that restored 5 V when disconnected.n


NO - Go to 56.


56.Turn the ignition switch OFF.

57.Disconnect the 3P connector from the following sensors.

  • Throttle position (TP) sensor
  • Mainshaft speed sensor (KP, KT, KU, KZ models (A/T))

58.Disconnect ECM/PCM connector A (31P).

59.Check for continuity between ECM/PCM connector terminal A20 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the  ECM/ PCM (A20) and the  TP sensor, mainshaft speed sensor (KP, KT, KU, KZ models (A/T)).n


NO - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original  ECM/ PCM.n


60.Measure voltage between body ground and ECM/PCM connector terminals E5.

 

Is there about 5 V?


YES - Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original  ECM/ PCM.n


NO - Go to 61.


61.Turn the ignition switch OFF, and disconnect the idle mixture adjuster (IMA) 3P connector.

62.Turn the ignition switch ON (II).

63.Measure voltage between body ground and ECM/PCM connector terminal E5.

 

Is there about 5 V?


YES - Replace the IMA.n


NO - Go to 64.


64.Turn the ignition switch OFF.

65.Disconnect ECM/PCM connector E (31P).

66.Check for continuity between ECM/PCM connector terminal E5 and body ground.

 

Is there continuity?


YES - Repair short in the wire between  ECM/ PCM (E5) and the IMA.n


NO - Substitute a known-good ECM/PCM and recheck. If the symptom/indication goes away, replace the original  ECM/ PCM.n

67.Turn the ignition switch OFF.

68.Turn the ignition switch ON (II).

69.Measure voltage between ECM/PCM connector terminal E29 and body ground.

 

Is there about 5 V (or battery voltage)?


YES - Go to 73.


NO - Go to 70.


70.Turn the ignition switch OFF.

71.Disconnect the ECM/PCM connector E (31P).

72.Check for continuity between ECM/PCM connector terminal E29 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the  data link connector and the  ECM/ PCM (E29).n


NO - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original  ECM/ PCM.n


73.Turn the ignition switch OFF.

74.Disconnect the ECM/PCM connector E (31P).

75.Turn the ignition switch ON (II).

Is the MIL ON?


YES - Repair short in the wire between the gauge assembly and the  ECM/ PCM (E31). If the wires are OK, replace the gauge assembly.n


NO - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original  ECM/ PCM.n