P1641

Diagnostic Chart:

Wiring Diagram:

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.

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.