Circuit Description
A dash light is illuminated by the PCM if diagnostics have detected certain errors related to the engine performance or engine sensor status. When the PCM is commanding the MIL ON, the voltage potential of the circuit will be low (near 0 volts). When the PCM is commanding the MIL OFF, the voltage potential of the circuit will be high (near battery volts). The primary function of the PCM is to supply the ground for the MIL circuit. This is a type D DTC
Conditions for Setting the DTC
| • | MIL requested ON. |
| • | Voltage on MIL control circuit high (near battery volts). |
or
| • | MIL requested OFF. |
| • | Voltage on MIL control circuit low (near 0 volts). |
Action Taken When the DTC Sets
Will not turn ON the MIL.
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle. |
| • | Use of a Scan tool |
Diagnostic Aids
A faulty bulb, the control circuit shorted to ground or battery voltage, will cause a P1641 to set.
An intermittent can be caused by the following:
| • | Poor connections |
| • | Rubbed through wire insulation |
| • | Broken wire inside the insulation |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
Be sure that both the ON and the OFF states are commanded. Repeat the commands as many times as necessary.
-
If no trouble is found in the control circuit or the connection at the PCM, the PCM maybe malfunctioning, however, this is an extremely unlikely failure.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing DTCs use the scan tool to record freeze frame and failure records for reference, as data will be lost when Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||
Does the lamp turn ON and OFF with each command? | -- | |||||||||
3 | DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored refer to those table(s). Are any additional DTCs stored? | -- | Go to the Applicable DTC table | Go to Diagnostic Aids | ||||||
4 |
Is the lamp OFF? | -- | ||||||||
5 |
Is the lamp ON? | -- | ||||||||
6 |
Was a repair performed? | -- | ||||||||
7 | MIL control circuit is shorted to ground, repair as necessary. Is the action complete? | -- | -- | |||||||
8 | Check the MIL circuit for the following:
Is the repair complete? | -- | -- | |||||||
Replace the PCM. Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .Is the action complete? | -- | -- | ||||||||
10 |
Does the Scan Tool indicate that this diagnostic Passed? | -- | ||||||||
11 | Using the Scan Tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go the Applicable DTC Table | System OK |
