Circuit Description
The PCM operates a solenoid to control boost. This solenoid is normally open. By providing a ground path the PCM energizes the solenoid which then allows vacuum to pass to the wastegate valve. During normal operation, the PCM compares its wastegate duty cycle signal with the boost signal and makes corrections in the duty cycle accordingly.
Conditions for Running the DTC
โข The PCM performs this DTC diagnostic continuously.
โข The ignition switch is in the ON position.
Conditions for Setting the DTC
โข The boost pressure is less than 40 kPa.
โข All diagnostic conditions met for 10 seconds.
Action Taken When the DTC Sets
โข The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.
โข The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records will 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
โข The PCM will turn the MIL off after three consecutive trips without a fault condition.
โข A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures
โข The use of a scan tool.
Diagnostic Aids
Very little boost can be attained by rewing the engine in neutral. If the boost sensor signal circuit is open or shorted to ground, the boost solenoid will show a zero duty cycle.
An intermittent may be caused by the following:
โข Poor connections.
โข Rubbed through wire insulation.
โข Broken wire inside the insulation.
Test Description
Number(s) bel ow refer to the step number(s) on the Diagnostic Table.
2. This step will determine if DTC P0237 is the result of a hard failure or an intermittent condition.
3. This step simulates conditions for a DTC P0237. If the PCM recognizes the change, the PCM and signal circuit are O K.
9. In this step, components that share the 5 volt reference can cause the reference voltage to be shorted to ground. This can be checked by disconnecting each component that shares the 5 volt reference one at a time, including the PCM while checking for continuity on that circuit to chassis ground.
