P1666

DTC P1666

Circuit Description

The powertrain control module (PCM) controls the Engine Shutdown Alarm by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the fault line status will change causing the DTC to set.

Conditions for Running the DTC

* The engine speed is more than 400 RPM.
* The ignition voltage is between 6-18 volts.

Conditions for Setting the DTC

The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match for a minimum of 5 seconds.

Action Taken When the DTC Sets

* The control module stores the DTC information into memory when the diagnostic runs and fails.
* The malfunction indicator lamp (MIL) will not illuminate.
* The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
* The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

* A current DTC Last Test Failed clears when the diagnostic runs and passes.
* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
* Clear the DTC with a scan tool.

Diagnostic Aids

* If the ignition feed circuit is suspected of being open, inspect for other lamps on that circuit not illuminating. An open fuse causes the entire cluster to be inoperative. Also, if the fuse is open, transmission DTCs set.
* Using Freeze Frame and Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame/nd Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass or a fail. Operate vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that were noted. This will isolate when the DTC failed. For an intermittent, refer to Intermittent Conditions Intermittent Conditions.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. Command both the ON and the OFF states. Repeat the commands as necessary.
8. If you do not find trouble in the control circuit or the connection at the PCM, the PCM may be faulty. However, this is an extremely unlikely failure.