MIL Circuit Troubleshooting
MIL Circuit Troubleshooting1. Connect the HDS.
2. Turn the ignition switch ON (II), and check the HDS.
Does the HDS communicate with the ECM?
YES - Go to step 3.
NO - Go to "DLC Circuit Troubleshooting".
3. Check for Temporary DTCs or DTCs with the HDS.
Are any Temporary DTCs or DTCs indicated?
YES - Go to the indicated DTC's troubleshooting.
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 81. But if the MIL sometimes works normally, first check for these problems:
- An intermittent short in the wire between the ECM (B17) and the data link connector (DLC).
- An intermittent short in the wire between the ECM (A18) and the gauge assembly.
- The readiness codes are not set. (This is indicated if the MIL blinks five times after you turn the ignition switch ON (II) and wait about 20 seconds.)
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.6 (7.5 A) fuse in the under-dash fuse/relay box.
- A loose No.1 (50 A) fuse in the under-hood fuse/relay box.
- A loose No. 7 (15 A) fuse in the under-hood fuse/relay box.
- A loose No.2 (15 A) fuse in the under-dash fuse/relay box.
- A poor connection at ECM terminal A18.
- An intermittent open in the GRN/ORN wire between the ECM (A18) and the gauge assembly.
- An intermittent short in the wire between the ECM (C19) and the manifold absolute pressure (MAP) sensor.
- An intermittent short in the wire between the ECM (C28) and the throttle position (TP) sensor, the brake booster pressure sensor, the fuel tank pressure (FTP) sensor, or the exhaust gas recirculation (EGR) valve position sensor.
- An intermittent short in the wire between the ECM (C23) and brake fluid pressure sensor B.
- An intermittent short in the wire between the ECM (B6) and the TCM (CVT model).
6. Turn the ignition switch OFF.
7. Turn the ignition switch ON (II).
Is the low oil pressure indicator on?
YES - Go to step 10.
NO - Go to step 8.
8. Inspect the No.6 (7.5 A) fuse in the under-dash fuse/relay box.
Is the fuse OK?
YES - Go to step 9.
NO - Repair short in the wire between the No.6 (7.5 A) fuse and the gauge assembly. Also replace the No.6 (7.5 A) fuse.
9. Inspect the No.1 (50 A) fuse in the under-hood fuse/relay box.
Is the fuse OK?
YES - Repair open in the wire between the No.1 (50 A) fuse and the gauge assembly. If the wires are OK, test the ignition switch.
NO - Repair short in the wire between the No.1 (50 A) fuse and the under-dash fuse/relay box. Also replace the No.1 (50 A) fuse.
10. Try to start the engine.
Does the engine start?
YES - Go to step 11.
NO - Go to step 14.
11. Turn the ignition switch OFF.
12. Connect ECM connector terminal A18 to body ground with a jumper wire.
13. Turn the ignition switch ON (II).
Is the MIL on?
YES - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
NO - Check for an open in the wire between the ECM (A18) and the gauge assembly. Also check for a blown MIL bulb. If the wires and the bulb are OK, replace the gauge assembly.
14. Turn the ignition switch OFF.
15. Inspect the No.7 (15 A) fuse in the under-hood fuse/relay box.
Is the fuse OK?
YES - Go to step 22.
NO - Go to step 16.
16. Remove the blown No.7 (15 A) fuse in the under-hood fuse/relay box.
17. Remove the PGM-FI main relay (IGP).
18. Check for continuity between body ground and PGM-FI main relay (IGP) 4P connector terminals No.2 and No.4 individually.
Is there continuity?
YES - Repair short in the wire between the No.7 (15 A) fuse and the PGM-FI main relay (IGP). Also replace the No.7 (15 A) fuse.
NO - Go to step 19.
19. Disconnect the connectors from these components:
- PGM-FI main relay (FUEL PUMP)
- ECM connector B (25P)
- Injectors
- Idle air control (IAC) valve
20. Check for continuity between PGM-FI main relay (IGP) 4P connector terminal No.1 and body ground.
Is there continuity?
YES - Repair short in YEL/BLK wire between the PGM-FI main relay (IGP) and each item. Also replace the No.7 (15 A) fuse.
NO - Go to step 21.
21. Reconnect each of the components of the connectors below, one at a time, and check for continuity between PGM-FI main relay (IGP) 4P connector terminal No.1 and body ground.
- PGM-FI main relay (FUEL PUMP)
- ECM connector B (25P)
- Each injector 2P connector
- Idle air control (IAC) valve 3P connector
Is there continuity?
YES - Replace the component that made continuity to body ground go away when disconnected. If the item is the ECM, update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM. Also replace the No.7 (15 A) fuse.
NO - Replace the PGM-FI main relay (IGP). Also replace the No.7 (15 A) fuse.
22. Inspect the No.2 (15 A) fuse in the under-dash fuse/relay box.
Is the fuse OK?
YES - Go to step 32.
NO - Go to step 23.
23. Remove the blown No.2 (15 A) fuse in the under-dash fuse/relay box.
24. Remove ECM connector A (32P).
25. Check for continuity between ECM connector terminal A26 and body ground.
Is there continuity?
YES - Go to step 26.
NO - Replace the No.2 (15 A) fuse, and update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
26. Remove PGM-FI main relay (FUEL PUMP).
27. Check for continuity between ECM connector terminal A26 and body ground.
Is there continuity?
YES - Repair short in the wire between the No.2 (15 A) fuse and the ECM (A26), or the No.2 (15 A) fuse and the PGM-FI main relay (FUEL PUMP). Also replace the No.2 (15 A) fuse.
NO - Go to step 28.
28. Remove the fuel tank.
29. 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 (FUEL PUMP). Also replace the No.2 (15 A) fuse.
NO - Go to step 30.
30. Reinstall the PGM-FI main relay (FUEL PUMP).
31. Check for continuity between fuel pump 5P connector terminal No.5 and body ground.
Is there continuity?
YES - Replace the PGM-FI main relay (FUEL PUMP). Also replace the No.2 (15 A) fuse.
NO - Check the fuel pump, and replace it if necessary. Also replace the No.2 (15 A) fuse.
32. Turn the ignition switch ON (II).
33. Measure voltage between ECM connector terminal A26 and body ground.
Is there battery voltage?
YES - Go to step 34.
NO - Repair open in the wire between the No.2 (15 A) fuse and the ECM (A26).
34. Turn the ignition switch OFF.
35. Measure voltage between ECM connector terminal A8 and body ground.
Is there battery voltage?
YES - Go to step 41.
NO - Go to step 36.
36. Remove PGM-FI main relay (IGP).
37. Measure voltage between PGM-FI main relay (IGP) 4P connector terminal No.4 and body ground.
Is there battery voltage?
YES - Go to step 38.
NO - Repair open in the wire between the No.7 (15 A) fuse and the PGM-FI main relay (IGP).
38. Disconnect ECM connector A (32P).
39. Connect ECM connector A8 to body ground with a jumper wire.
40. Check for continuity between body ground and PGM-FI main relay (IGP) 4P connector terminal No.3
Is there continuity?
YES - Replace the PGM-FI main relay (IGP).
NO - Repair open in the wire between the PGM-FI main relay (IGP) and the ECM (A8).
41. Turn the ignition switch ON (II).
42. Measure voltage between body ground and ECM connector terminals B1 and B9 individually.
Is there battery voltage?
YES - Go to step 49.
NO - Go to step 43.
43. Turn the ignition switch OFF.
44. Remove the PGM-FI main relay (IGP).
45. Turn the ignition switch ON (II).
46. Measure voltage between PGM-FI main relay (IGP) 4P connector terminal No.2 and body ground.
Is there battery voltage?
YES - Go to step 47.
NO - Repair open in the wire between the No.7 (15 A) fuse and the PGM-FI main relay (IGP)
47. Turn the ignition switch OFF.
48. Check for continuity between PGM-FI main relay (IGP) 4P connector terminal No.1 and ECM connector terminals B1 and B9 individually.
Is there continuity?
YES - Replace the PGM-FI main relay (IGP).
NO - Repair open in the wire between the PGM-FI main relay (IGP) and the ECM (B1, B9).
49. Measure voltage between body ground and ECM connector terminals B2, B10, B20, and B22 individually.
Is there more than 1.0 V?
YES - Repair open in the wire(s) that had more than 1.0 V between G101 and the ECM (B2, B10, B20, B22).
NO - Go to step 50.
50. Measure voltage between body ground and ECM connector terminal C19.
Is there about 5 V?
YES - Go to step 58.
NO - Go to step 51.
51. Turn the ignition switch OFF.
52. Disconnect the manifold absolute pressure (MAP) sensor 3P connector.
53. Turn the ignition switch ON (II).
54. Measure voltage between body ground and ECM connector terminal C19.
Is there about 5 V?
YES - Replace the MAP sensor.
NO - Go to step 55.
55. Turn the ignition switch OFF.
56. Disconnect ECM connector C (31P).
57. Check for continuity between ECM connector terminal C19 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM (C19) and the MAP sensor.
NO - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
58. Measure voltage between body ground and ECM connector terminal C28.
Is there about 5 V?
YES - Go to step 65.
NO - Go to step 59.
59. Turn the ignition switch OFF.
60. Disconnect the 3P connector from each of these sensors, one at a time, and measure voltage between body ground and ECM connector terminal C28 with the ignition switch ON (II).
- Exhaust gas recirculation (EGR) valve position sensor
- Brake booster pressure sensor
- Fuel tank pressure (FTP) sensor
- Throttle position (TP) sensor
- Brake fluid pressure sensor A
Is there about 5 V?
YES - Replace the sensor that restored about 5 V when disconnected.
NO - Go to step 61.
61. Turn the ignition switch OFF.
62. Disconnect the connector from these sensors:
- Exhaust gas recirculation (EGR) valve position sensor
- Brake booster pressure sensor
- Fuel tank pressure (FTP) sensor
- Throttle position (TP) sensor
- Brake fluid pressure sensor A
63. Disconnect ECM connector C (31P).
64. Check for continuity between ECM connector terminal C28 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM (C28) and the EGR valve position sensor, the brake booster pressure sensor, the FTP sensor, the TP sensor, or brake fluid pressure sensor A.
NO - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
65. Measure voltage between body ground and ECM connector terminal C23.
Is there about 5 V?
YES - Go to step 73.
NO - Go to step 66.
66. Turn the ignition switch OFF.
67. Disconnect the brake fluid pressure sensor B 3P connector.
68. Turn the ignition switch ON (II).
69. Measure voltage between body ground and ECM connector terminal C23.
Is there about 5 V?
YES - Replace brake fluid pressure sensor B.
NO - Go to step 70.
70. Turn the ignition switch OFF.
71. Disconnect ECM connector C (31P).
72. Check for continuity between ECM connector terminal C23 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM (C23) and brake fluid pressure sensor B.
NO - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
73. Measure voltage between body ground and ECM connector terminal B6.
Is there about 5 V?
YES - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
NO - Go to step 74.
74. Turn the ignition switch OFF.
75. Disconnect TCM connector B (22P).
76. Turn the ignition switch ON (II).
77. Measure voltage between body ground and ECM connector terminal B6.
Is there about 5 V?
YES - Substitute a known-good TCM, and recheck. If the symptom/indication goes away, replace the original TCM.
NO - Go to step 78.
78. Turn the ignition switch OFF.
79. Disconnect ECM connector B (25P).
80. Check for continuity between ECM connector terminal B6 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM (B6) and the TCM (B20).
NO - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
81. Measure voltage between ECM connector terminal B17 and body ground.
Is there about 5 V (or battery voltage)?
YES - Go to step 85.
NO - Go to step 82.
82. Turn the ignition switch OFF.
83. Disconnect ECM connector B (25P).
84. Check for continuity between ECM connector terminal B17 and body ground.
Is there continuity?
YES - Repair short in the wire between the DLC and the ECM (B17).
NO - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
85. Turn the ignition switch OFF.
86. Disconnect ECM connector B (25P).
87. Turn the ignition switch ON (II).
Is the MIL on?
YES - Repair short in the wire between the gauge assembly and the ECM (B17). If the wire is OK, replace the gauge assembly.
NO - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.