P1656

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 (PWM) solenoid meters the vacuum level at the wastegate valve actuator as commanded by the powertrain control module (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, test 1.
or
The PCM requested the wastegate solenoid OFF, test 2.

CONDITIONS FOR SETTING THE DTC
^ The voltage on the wastegate solenoid control circuit is high, near the battery voltage, for test 1.
^ 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, for test 2.
^ Two consecutive faults have been detected.
^ The conditions met for 2 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ 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 emission related diagnostic.
^ Clear the MIL and the DTC with a scan tool.

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 more than barometric pressure (BARO) at idle. The engine will also not respond to the scan tool commands at any engine speed which is more than the idle. The PCM control abort in order to prevent the engine damage.

TEST DESCRIPTION

Steps 1-6:

Steps 7-16:

The numbers below refer to the step numbers on the diagnostic table.

2. This step will determine if this DTC is a current or an intermittent.
3. This check can detect a partially shorted coil which would cause an excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm, the coil may open, the amps drop to zero, or short an amp drawn more than 0.75 amp.