Circuit Description
There should always be a steady MIL with the ignition ON and the engine stopped. Ignition feed voltage is supplied directly to the MIL bulb. The Powertrain Control Module (PCM) turns the MIL ON by grounding the MIL driver circuit. No MIL with the key ON, engine not running and DTC P1641 set suggests an open in the MIL driver circuit.
Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following items:
| • | Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness. |
| • | If the engine runs OK, check for a faulty light bulb, an open in the MIL driver circuit, or an open in the instrument cluster ignition feed. |
| • | If the engine cranks but will not run, check for an open PCM ignition or battery feed or a poor PCM to engine ground. |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
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A no MIL condition accompanied by a no start condition suggests a faulty PCM ignition feed or battery feed circuit.
-
Using a test light connected to battery positive voltage, probe each of the PCM ground terminals to ensure that a good ground is present. Refer to Engine Controls Component Views for terminal locations of the PCM ground circuits.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain OBD System Check? | -- | ||
Attempt to start the engine. Does the engine start? | -- | |||
3 | Inspect the fuse for the instrument cluster ignition feed circuit. Is the fuse OK? | -- | ||
4 |
Is the test lamp on? | -- | ||
5 |
Is the MIL ON? | -- | ||
6 | Inspect the PCM ignition feed fuse and the battery feed fuse. Are both of the fuses OK? | -- | ||
7 |
Is the test lamp on? | -- | ||
8 | Use a test lamp in order to probe the battery feed circuit between the PCM harness connector and ground. Is the test lamp on? | -- | ||
Is the circuit OK? | -- | |||
10 |
Is the circuit OK? | -- | ||
11 |
Is the circuit OK? | -- | ||
12 | Repair an open in the ignition feed circuit to the instrument panel indicators. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
13 | Locate and repair an open in the PCM battery feed circuit or the PCM ignition feed circuit as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | --- | |
14 | Locate and repair a short to ground in the PCM ignition feed circuit or the PCM battery feed circuit as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | --- | |
15 | Locate and repair a short to ground in the ignition feed circuit of the instrument panel indicators. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |
|
Important: : The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | -- | ||
17 |
Is the MIL driver circuit OK? | -- | -- |
