P1656

DTC P1656 Wastegate Solenoid Control Circuit






Circuit Description

The turbocharger wastegate is a vacuum actuated valve which is used in order to control the exhaust gas heat which is sent to the turbo. The wastegate pulse width modulated solenoid meters the vacuum level at the wastegate valve actuator as commanded by the PCM. When the PCM is commanding the wastegate solenoid ON, the voltage potential of the circuit will be low (near 0 volts). When the PCM is commanding the wastegate solenoid OFF, the voltage potential of the circuit will be high (near the battery voltage). The primary function of the PCM in this circuit is to supply the ground for the wastegate solenoid.

Conditions for Running the DTC

The PCM requested the wastegate solenoid ON.

or

The PCM requested the wastegate solenoid OFF.

Conditions for Setting the DTC

^ The voltage on the wastegate solenoid control circuit is high (near the battery voltage).
^ Two consecutive faults have been detected.
^ The conditions were met for 2 seconds. or
^ The voltage on the wastegate solenoid control circuit is low (near 0 volts).
^ Two consecutive faults have been detected.
^ The conditions were met for 2 seconds.

Action Taken When the DTC Sets

^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip the diagnostic mns and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records.

Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL off after three consecutive trips without a fault condition.
^ A History DTC will clear after forty consecutive engine warm up cycles, if this or any other emission related diagnosic does not report any failures.
^ Use of a scan tool will clear the DTC codes.

Diagnostic Aids

This diagnostic will set when the control circuit does not follow the PCM command (when the solenoid is requested ON, the voltage will drop; when the solenoid is OFF, the ignition voltage will be present). The scan tool has a 5 second ON time abort. The wastegate solenoid can be commanded ON for as many times as needed, in 5 second intervals. DTC P0236 may possibly set along with DTC P1656. This diagnostic can be checked during key up. The engine will not respond to the scan tool commands at the idle (the engine is unable to achieve the boost pressures that are greater than BARO at idle) or at any engine speed which is greater than the idle (the PCM control aborts in order to prevent the engine damage).

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

2. Checks that both the ON and OFF states are commanded. Repeat the commands as many times as necessary.
3. This check can detect a partially shorted coil which would cause excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm, the coil may open (amps drop to zero), or short (amp draw greater than 0.75 A).
14. If no trouble is found in the control circuit or the connection at the PCM, the PCM may be malfunctioning. However, this is an extremely unlikely failure.