P1641

DTC P1641 MIL Control Circuit

Circuit Description

A dash light is illuminated by the PCM if the diagnostics have detected certain errors related to the engine performance or the 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.

Conditions for Running the DTC

The MIL is requested ON.
or
The MIL is requested OFF.

Conditions for Setting the DTC

The voltage on the MIL control circuit is high (near the battery voltage).
or
The voltage on the MIL control circuit is low (near 0 volts).

Action Taken When the DTC Sets

^ The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Failure Records.

Conditions for Clearing the MIL/DTC

^ A History DTC will clear after forty consecutive warm-up cycles, it this or any other emission related diagnostic does not report any failures.
^ Use of a scan tool will clear the DTC codes.

Diagnostic Aids

A malfunctioning bulb, the control circuit shorted to ground or battery voltage, will cause a P1641 to set.

An intermittent may 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.

2. Be sure that both the ON and the OFF states are commanded. Repeat the commands as many times as necessary.
9. 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.