Circuit Description
The powertrain control module (PCM) controls boost using the turbocharger wastegate solenoid. The solenoid is pulse width modulated (PWM). When the wastegate solenoid is not energized, the vacuum to the turbocharger wastegate solenoid is vented to atmosphere through the solenoid. As the pulse width is increased by the PCM, more vacuum is applied through the solenoid to the wastegate actuator. At idle a higher vacuum to the wastegate actuator helps keep the wastegate closed. At higher engine speeds the vacuum supplied by the solenoid is less, allowing the turbocharger boost pressure to overcome the wastegate actuator.
Conditions for Running the DTC
| • | The PCM performs this diagnostic trouble code (DTC) diagnostic continuously. |
| • | The ignition is in the ON position. |
Conditions for Setting the DTC
| • | The boost pressure is less than 40 kPa. |
| • | All diagnostic conditions are met for 10 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
Very little boost can be attained by revving 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 conditions:
| • | Poor connections |
| • | Rubbed through wire insulation |
| • | Broken wire inside the insulation |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step will determine if DTC P0237 is the result of a hard failure or an intermittent condition.
-
This step simulates conditions for a DTC P0237. If the PCM recognizes the change, the PCM and signal circuit are OK.
-
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.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||
Does the scan tool display a Boost Pressure less than or equal to the specified value? | 40 kPa | Go to Step 3 | Go to Step 5 | |||||
Does the scan tool display a Boost Pressure more than or equal to the specified value? | 202 kPa | Go to Step 6 | Go to Step 4 | |||||
4 |
Does the scan tool display a Boost Pressure more than or equal to the specified value? | 202 kPa | Go to Step 8 | Go to Step 7 | ||||
5 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs are stored, refer to those tables first. Are any additional DTCs stored? | -- | Go to Diagnostic Aids | |||||
6 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||
7 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||
8 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 | ||||
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | |||||
10 | Replace the boost sensor. Refer to Boost Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||
11 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||
13 |
Does the DTC run and pass? | -- | Go to Step 14 | Go to Step 2 | ||||
14 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
