MIL Circuit Troubleshooting
MIL Circuit Troubleshooting1. Connect the HDS.
2. Turn the ignition switch ON (II), and read 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 86. But if the MIL sometimes works normally, first check for these problems.
- An intermittent short in the wire between the ECM (E29) and the data link connector (DLC).
- An intermittent short in the wire between the ECM (E31) and the gauge assembly.
- The readiness codes are not set. (This is indicated if the MIL blinks several 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.10 METER (7.5 A) fuse in the under- dash fuse/relay box.
- A loose No.20 IG1 (50 A) fuse in the under-hood fuse/relay box.
- A loose No.6 ECU (ECM) (15 A) fuse in the under- hood fuse/relay box.
- A loose No.17 FUEL PUMP (15 A) fuse in the under-dash fuse/relay box.
- A poor connection at ECM terminal E31.
- An intermittent open in the GRN/WHT wire between the ECM (E31) and the gauge assembly.
- An intermittent short in the wire between the ECM (A21) and the manifold absolute pressure (MAP) sensor.
- An intermittent short in the wire between the ECM (A20) and the throttle position (TP) sensor, exhaust gas recirculation (EGR) valve position sensor, or engine oil pressure (EOP) sensor.
- An intermittent short in the wire between the ECM (E5) and the fuel tank pressure (FTP) sensor or brake booster pressure sensor.
- An intermittent short in the wire between the ECM (C17) and TCM (CVT model).
6. Check the low oil pressure indicator (with the ignition switch ON (II)).
Is the low oil pressure indicator on?
YES - Go to step 9.
NO - Go to step 7.
7. Inspect the No.10 METER (7.5 A) fuse in the under- dash fuse/relay box.
Is the fuse OK?
YES - Go to step 8.
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.
8. 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 IG1 (50 A) fuse and the gauge assembly. If the wires are OK, test the ignition switch.
NO - Repair short in the wire between No.20 IG1 (50 A) fuse and the under-dash fuse/relay box. Also replace the No.20 IG1 (50 A) fuse.
9. Try to start the engine.
Does the engine start?
YES - Go to step 10.
NO - Go to step 13.
10. Turn the ignition switch OFF.
11. Connect ECM connector terminal E31 to body ground with a jumper wire.
12. 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 (E31) and the gauge assembly. Also check for a blown MIL bulb. If the wires and the bulb are OK, replace the gauge assembly.
13. Turn the ignition switch OFF.
14. Inspect the No.6 ECU (ECM) (15 A) fuse in the under-hood fuse/relay box.
Is the fuse OK?
YES - Go to step 22.
NO - Go to step 15.
15. Remove the blown No.6 ECU (ECM) (15 A) fuse from the under-dash fuse/relay box.
16. Remove the glove box.
17. Remove PGM-FI main relay 1 (A).
18. 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 No.6 ECU (ECM) (15 A) fuse and PGM-FI main relay 1. Also replace the No.6 ECU (ECM) (15 A) fuse.
NO - Go to step 19.
19. Disconnect each of the components or connectors below, one at a time, and check for continuity between PGM-FI main relay 1 4P connector terminal No.1 and body ground:
- PGM-FI main relay 2
- ECM connector A (31P)
- Each injector 2P connector
- Idle air control (IAC) valve 3P connector
- Cam position (CMP) sensor 3P connector
- Crankshaft position (CKP) sensor 3P connector
- Hot restart fan relay
Is there continuity?
YES - Go to step 20.
NO - Replace the component that made the short 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.6 ECU (ECM) (15 A) fuse.
20. Disconnect the connectors of all these components:
- PGM-FI main relay 2
- ECM connector A (31P)
- Injectors
- Idle air control (IAC) valve
- Cam position (CMP) sensor
- Crankshaft position (CKP) sensor
- Hot restart fan relay
21. Check for continuity between PGM-FI main relay 1 4P connector terminal 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 No.6 ECU (ECM) (15 A) fuse.
NO - Replace PGM-FI main relay 1. Also replace the No.6 ECU (ECM) (15 A) fuse.
22. Inspect the No.17 FUEL PUMP (15 A) fuse in the under-dash fuse/relay box.
Is the fuse OK?
YES - Go to step 35.
NO - Go to step 23.
23. Remove the blown No.17 FUEL PUMP (15 A) fuse from the under-dash fuse/relay box.
24. Wait for 1 minute. If the radiator fan is running, wait for 1 minute after it stops.
25. Disconnect ECM connector E (31P).
26. Check for continuity between ECM connector terminal E9 and body ground.
Is there continuity?
YES - Go to step 27.
NO - Replace the No.17 FUEL PUMP (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.
27. Remove PGM-FI main relay 2 (A).
28. Check for continuity between ECM 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 (E9), or between the No.17 FUEL PUMP (15 A) fuse and PGM-FI main relay 2. Also replace the No.17 FUEL PUMP (15 A) fuse.
NO - Go to step 29.
29. Remove the rear seat cushion.
30. Remove the access panel from the floor.
31. Disconnect the fuel pump 5P connector.
32. 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 PGM-FI main relay 2. Also replace the No.17 FUEL PUMP (15 A) fuse.
NO - Go to step 33.
33. Reinstall PGM-FI main relay 2 (A).
34. 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.
NO - Check the fuel pump, and replace it if necessary. Also replace the No.17 FUEL PUMP (15 A) fuse.
35. Wait for 1 minute. If the radiator fan is running, wait for 1 minute after it stops.
36. Disconnect ECM connector E (31P).
37. Turn the ignition switch ON (II).
38. Measure voltage between ECM connector terminal E9 and body ground.
Is there battery voltage?
YES - Go to step 39.
NO - Repair open in the wire between the No.17 FUEL PUMP (15 A) fuse and the ECM (E9).
39. Measure voltage between ECM connector terminal E7 and body ground.
Is there battery voltage?
YES - Go to step 44.
NO - Go to step 40.
40. Turn the ignition switch OFF.
41. Remove PGM-FI main relay 1 (A).
42. Measure voltage between PGM-FI main relay 1 4P connector terminal No.4 and body ground.
Is there battery voltage?
YES - Go to step 43.
NO - Repair open in the wire between the No.6 ECU (ECM) (15 A) fuse and PGM-FI main relay 1.
43. Check for continuity between PGM-FI main relay 1 4P connector terminal No.3 and ECM connector terminal E7.
Is there continuity?
YES - Test PGM-FI main relay 1. If the relay is OK, 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 - Repair open in the wire between PGM-FI main relay 1 and the ECM (E7).
44. Turn the ignition switch OFF.
45. Reconnect ECM connector E (31P).
46. Turn the ignition switch ON (II).
47. Measure voltage between body ground and ECM connector terminals A2 and A3 individually.
Is there battery voltage?
YES - Go to step 54.
NO - Go to step 48.
48. Turn the ignition switch OFF.
49. Remove PGM-FI main relay 1 (A).
50. Turn the ignition switch ON (II).
51. Measure voltage between PGM-FI main relay 1 4P connector terminal No.2 and body ground.
Is there battery voltage?
YES - Go to step 52.
NO - Repair open in the wire between the No.6 ECU (ECM) (15 A) fuse and PGM-FI main relay 1.
52. Turn the ignition switch OFF.
53. Check for continuity between PGM-FI main relay 1 4P connector terminal No.1 and ECM connector terminals A2 and A3 individually.
Is there continuity?
YES - Replace PGM-FI main relay 1.
NO - Repair open in the wire between PGM-FI main relay 1 and the ECM (A2, A3).
54. Measure voltage between body ground and ECM connector terminals A4, AS, A23, and A24 individually.
Is there more than 0.2 V?
YES - Repair open in the wire(s) that had more than 0.2 V between G101 and the ECM (A4, A5, A23, A24).
NO - Go to step 55.
55. Measure voltage between body ground and ECM connector terminal A21.
Is there about 5 V?
YES - Go to step 62.
NO - Go to step 56.
56. Turn the ignition switch OFF.
57. Disconnect the manifold absolute pressure (MAP) sensor 3P connector, and measure voltage between body ground and ECM connector terminal A21 with the ignition switch ON (II).
Is there about 5 V?
YES - Replace the MAP sensor.
NO - Go to step 58.
58. Turn the ignition switch OFF.
59. Wait for 1 minute. If the radiator fan is running, wait for 1 minute after it stops.
60. Disconnect ECM connector A (31P).
61. Check for continuity between ECM connector terminal A21 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM (A21) 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.
62. Measure voltage between body ground and ECM connector terminal A20.
Is there about 5 V?
YES - Go to step 70.
NO - Go to step 63.
63. Turn the ignition switch OFF.
64. Disconnect the 3P connector from each of the following sensors, one at a time, and measure voltage between body ground and ECM connector terminal A20 with the ignition switch ON (II):
- Throttle position (TP) sensor
- Exhaust gas recirculation (EGR) valve position sensor
- Engine oil pressure (EOP) sensor
Is there about 5 V?
YES - Replace the sensor that restored 5 V when disconnected.
NO - Go to step 65.
65. Turn the ignition switch OFF.
66. Disconnect the 3P connectors from these sensors:
- Throttle position (TP) sensor
- Exhaust gas recirculation (EGR) valve position sensor
- Engine oil pressure (EOP) sensor
67. Wait for 1 minute. If the radiator fan is running, wait for 1 minute after it stops.
68. Disconnect ECM connector A (31P).
69. Check for continuity between ECM connector terminal A20 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM (A20) and the TP sensor, EGR valve position sensor, or EOP 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.
70. Measure voltage between body ground and ECM connector terminal E5.
Is there about 5 V?
YES -
- Go to step 77 (CVT model).
- Update the ECM it 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 (M/T model).
NO - Go to step 71.
71. Turn the ignition switch OFF.
72. Disconnect the 3P connector from each of the following sensors, one at a time, and measure voltage between body ground and ECM connector terminal E5 with the ignition switch ON (II):
- Fuel tank pressure (FTP) sensor
- Brake booster pressure sensor
Is there about 5 V?
YES - Replace the sensor that restored 5 V when disconnected.
NO - Go to step 73.
73. Turn the ignition switch OFF.
74. Wait for 1 minute. If the radiator fan is running, wait for 1 minute after it stops.
75. Disconnect ECM connector E (31P).
76. Check for continuity between ECM connector terminal E5 and body ground.
Is there continuity?
YES - repair short in the wire between the ECM (E5) and the FTP sensor or brake booster pressure 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.
77, Measure voltage between body ground and ECM connector terminal C7.
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 78.
78. Turn the ignition switch OFF.
79. Disconnect TCM connector C (17P).
80. Turn the ignition switch ON (II).
81. Measure voltage between body ground and ECM connector terminal C7.
Is there about 5 V?
YES - Update the TCM if it does not have the latest software, or substitute a known-good TCM, then recheck. If the symptom/indication goes away with a known-good TCM, replace the original TCM.
NO - Go to step 82.
82. Turn the ignition switch OFF.
83. Wait for 1 minute. If the radiator fan is running, wait for 1 minute after it stops.
84. Disconnect ECM connector C (22P).
85. Check for continuity between ECM connector terminal C7 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM (C7) and the TCM (C14).
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.
86. Turn the ignition switch OFF.
87. Turn the ignition switch ON (I!).
88. Measure voltage between ECM connector terminal E29 and body ground.
Is there about 5 V (or battery voltage)?
YES - Go to step 93.
NO - Go to step 89.
89. Turn the ignition switch OFF.
90. Wait for 1 minute. If the radiator fan is running, wait for 1 minute after it stops.
91. Disconnect ECM connector E (31P).
92. Check for continuity between ECM connector terminal E29 and body ground.
Is there continuity?
YES - Repair short in the wire between the DLC and the ECM (E29).
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.
93. Turn the ignition switch OFF.
94. Wait for 1 minute. If the radiator fan is running, wait for 1 minute after it stops.
95. Disconnect ECM connector E (31P).
96. Turn the ignition switch ON (II).
Is the MIL on?
YES - Repair short in the wire between the gauge assembly and the ECM (E31). If the wires are 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.