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. This diagnostic
will detect an overboost condition.
Conditions for Running the DTC
| • | The PCM performs this DTC diagnostic continuously. |
| • | P0238 and P0243 are not set. |
| • | The engine is operating. |
Conditions for Setting the DTC
| • | The boost pressure is greater than 20 kPa from desired
(desired boost pressure value is internal to the PCM). |
| • | All diagnostic set conditions met for 2 seconds. |
Action Taken When the DTC Sets
| • | A poor performance condition will exist (the PCM will limit fuel). |
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the
second consecutive drive trip that the diagnostic runs and fails. |
| • | 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
| • | The PCM will turn the MIL off after three consecutive trips without
a fault condition. |
| • | A History DTC will clear after forty consecutive warm-up
cycles, if this or any other emission related diagnostic does not report any
failures. |
Diagnostic Aids
A partially plugged or completely plugged vacuum line will cause a DTC
P0234. Check all vacuum lines and components connected to the hoses for sharp
bends. A plugged wastegate solenoid filter will cause this diagnostic to
set. Incorrect vacuum line routing will cause vacuum to always remain at
the wastegate actuator and cause an overboost condition. Check for proper
vacuum line routing. Refer to
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 orifice.
