Refer to
DIESEL PCM, EGR, SENSORS
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 Setting the DTC
| • | Engine speed greater than 2400 RPM. |
| • | Fuel rate greater than 20 mm. |
| • | Boost pressure is greater than, less than, or equal to 20 kPa from desired (internal to PCM). |
| • | Conditions met for 10 seconds. |
or
| • | Engine speed greater than 1800 but less than 2400 RPM. |
| • | Fuel rate greater than 20 mm. |
| • | Conditions met for 12 seconds. |
Action Taken When the DTC Sets
| • | Poor performance |
| • | Reduce maximum fuel. |
| • | No TCC |
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 when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle. |
| • | Use of a Scan Tool |
Diagnostic Aids
A vacuum leak or a pinched vacuum line may cause a DTC P0236. Check all vacuum lines and components connected to the hoses for leaks or sharp bends. Check vacuum source. A possible EGR DTC will store if there is a problem with the vacuum source. Also check for proper vacuum line routing.
The turbocharger wastegate actuator uses a pulse width modulated vacuum solenoid that causes vacuum to fluctuate under normal conditions. A steady vacuum reading indicates a restricted or plugged solenoid vent filter or solenoid vent orfice.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
This will check the wastegate solenoid and filter. If the filter is plugged, the filter will not allow the solenoid to vent and this will cause an overboost condition.
-
This step checks the turbocharger wastegate actuator for vacuum leaks. The actuator must hold vacuum.
-
This step will check for vacuum leaks at the lines.
-
This step will check for a skewed boost pressure sensor.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and failure records for reference. The control module's data is deleted once the Clear Info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
2 | Is the DTC P1656 also set? | -- | ||||||||
3 |
Is the vacuum greater than or equal to the specified value (vacuum will fluctuate)? | 15 in. Hg | ||||||||
Is the vacuum greater than the specified value? | 1 in. Hg | |||||||||
Does the turbocharger wastegate actuator hold vacuum? | -- | |||||||||
Was a problem found? | -- | |||||||||
7 |
Does the turbocharger wastegate actuator rod move freely? | -- | ||||||||
8 | Check the vacuum pump for proper output (refer to Engine Vacuum Pump Test in Engine Mechanical). Was a problem found? | -- | ||||||||
9 |
Is the vacuum more than the specified value? | 15 in Hg | ||||||||
10 |
Is the vacuum more than the specified value? | 15 in Hg | ||||||||
11 |
Does the test lamp illuminate? | -- | ||||||||
Does the scan tool display a change in boost pressure? | -- | |||||||||
13 | The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored, refer to those table(s). Are any additional DTCs stored? | -- | Go to the Applicable DTC Table | Go to Diagnostic Aids | ||||||
14 | Test the wastegate solenoid ignition 1 voltage circuit for a short to ground or an open. Repair as necessary. Did you find and correct the condition? | -- | ||||||||
15 | Test the wastegate solenoid control circuit for an open. Repair as necessary. Did you find and correct the condition? | -- | ||||||||
16 | Repair the vacuum leak between the vacuum pump and the wastegate solenoid. Did you complete the repair? | -- | -- | |||||||
17 | Repair the vacuum leak between the wastegate solenoid and the wastegate actuator. Did you complete the repair? | -- | -- | |||||||
18 | Replace the boost sensor. Refer to Boost Sensor (Diesel) . Is the action complete? | -- | -- | |||||||
19 | Check for a plugged wastegate solenoid filter. Repair as necessary. Is the wastegate solenoid filter plugged? | -- | ||||||||
20 | Replace the wastegate solenoid. Refer to Wastegate Solenoid . Is the action complete? | -- | -- | |||||||
21 | Replace the turbocharger wastegate actuator. Is the action complete? | -- | -- | |||||||
22 | Replace the vacuum pump. Is the action complete? | -- | -- | |||||||
23 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | |||||||
24 |
Does the scan tool indicate the diagnostic Passed? | -- | ||||||||
25 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the Applicable DTC Table | System OK |
