DTC Advanced Diagnostics: P0234
DTC P0234:Turbocharger Overboost Problem

General Description

The boost pressure control monitor is utilized to detect possible errors of the turbocharger system. The turbocharger consists of two elements, a turbine and a compressor, which are connected by a single shaft. The boost control apparatus consists of turbocharger wastegate control actuator that is connected to the turbocharger wastegate control valve passing through the turbine housing. The electronically controlled turbocharger wastegate control valve delivers the resulting boost pressure. In order to provide boost pressure control diagnosis, the actual boost pressure upstream of the throttle valve is monitored against desired boost pressure under certain conditions. There are two types of boost pressure control deviation errors distinguished. If either of the following errors is detected, the PCM detects a malfunction and stores a DTC.
Overcharging error: Negative boost pressure control deviation. The actual boost pressure exceeds the desired boost pressure value.
Undercharging error: Positive boost pressure control deviation. The desired boost pressure exceeds the actual boost pressure value.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Continuous
Sequence
None
Duration
0.5 second or more
DTC Type
One drive cycle, MIL on

Enable Conditions
Condition
Minimum
Maximum
Vehicle speed [Vehicle Speed]
2 mph (3 km/h)
–
[ ]: HDS Parameter

Malfunction Threshold
The difference between commanded pressure upstream throttle valve and measured pressure upstream throttle valve is 20 kPa (150 mmHg, 5.9 inHg) - 100 kPa (750 mmHg, 29.6 inHg) or more for at least 2 seconds.

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
Turbocharger wastegate control actuator stuck
Leakage in turbocharger system

Confirmation Procedure
Operating Condition
1.
Start the engine. Hold the engine speed [Engine Speed] at 3,000 rpm without load (in neutral) until the radiator fan comes on, then let it idle.
2.
Drive the vehicle at engine speed [Engine Speed] 3,200 rpm or more with high load.
Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected, the MIL comes on and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the PCM memory.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command.