Refer to
Cell 21: MIL and DLC
and to
Cell 21: Power and Ground
.
Circuit Description
The malfunction indicator lamp (MIL) illuminates when the ignition is ON, and the engine is OFF. Battery ignition voltage is supplied to the MIL. The powertrain control module will turn the MIL ON by grounding the lamp control circuit. Under normal conditions, the MIL is OFF when the engine is running.
Diagnostic Aids
Inspect for any of the following conditions:
| • | If the engine starts and runs OK, look for a faulty indicator bulb or for an open in the instrument cluster power circuit |
| • | If the MIL is not illuminated and the engine cranks but will not start, inspect for a faulty main relay. |
| • | If there is not any scan tool data, an illuminated MIL, and the engine cranks but will not start, check for a 5 volt reference circuit shorted to ground. |
| • | Inspect for a faulty electrical connection to the PCM. |
A fault in the MIL electrical circuit may cause an intermittent malfunction. Inspect the wiring harness and the components for any of the following conditions:
| • | Backed out terminals. |
| • | Incorrect mating of terminals. |
| • | Broken electrical connector locks. |
| • | Incorrectly formed terminals or damaged terminals. |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, of splices, or of terminals. |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
-
The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.
-
This step will verify if the MIL circuit is faulty, or if the PCM is not providing a ground path for the MIL circuit.
-
This step will verify the condition of the MIL control circuit. The PCM is providing the ground for the test light.
-
This step checks for an open in the ignition positive voltage circuits from the main relay. There is not any MIL control or any serial data with an open circuit between the last two splices before the PCM.The engine may start and run.
-
This step checks for a short to ground in the PCM 5 volt reference circuit. If the reference voltage circuit is shorted to ground, the MIL will not operate, and the engine will not start. Check the circuit wiring, the sensors, and the components for shorts to ground on the 5 volt reference circuit.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On--Board Diagnostic (OBD) System Check? | -- | |||||||||
2 | Check for an open in the following fuses:
Was an open fuse found? | -- | ||||||||
3 | Attempt to start the engine. Does the engine start? | -- | ||||||||
4 | Install a scan tool, and select the data display. Does the scan tool display any data? | -- | ||||||||
Does the MIL illuminate? | -- | |||||||||
6 |
Does the test lamp illuminate? | -- | ||||||||
Does the test lamp illuminate if the ignition switch is turned ON and turn OFF if the ignition switch is turned OFF? | -- | |||||||||
8 | Repair the open in the circuit between terminal C4-3 of the junction block and terminal C1-2 of the IP cluster assembly connector. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
9 | Locate and repair the open in the MIL control circuit between the instrument panel cluster assembly and the PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
Does the test light illuminate at each terminal? | -- | |||||||||
11 | Backprobe terminal C3-20 in the PCM electrical connector with a test lamp that is connected to ground. Does the test light illuminate? | -- | ||||||||
12 | Repair the open in the ignition positive voltage circuit between the IG-COIL fuse and the PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
13 |
Was a repair necessary? | -- | ||||||||
14 |
Was the measured voltage at the specified value? | 5 V | ||||||||
Was a repair necessary? | -- | |||||||||
16 |
Does the test light illuminate at each terminal? | -- | ||||||||
17 | Repair the open in the PCM ground circuits between the PCM and the G104 ground. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
18 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||||
19 |
Is the action complete? | -- | -- | |||||||
20 | Repair the short to ground in the IG-COIL fuse or in the FI fuse circuits. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
21 |
Did the MIL illuminate if the ignition was ON, and OFF after the engine was started? | -- | System OK | Go to the applicable diagnostic table |
