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Error Code P0234 is defined as Turbocharger / Supercharger “A” Overboost Condition Code.
This indicates the PCM (powertrain control module, also known as ECM or engine control module) has detected that the intake boost pressure sensor input signal receives pressure more than the maximum specified input pressure by 4 psi for over 5 seconds.
It’s a generic trouble code, meaning it applies to all vehicles equipped with OBD-II, particularly vehicles made in 1996 up to present. Specifications on the definition, troubleshooting, and repairs of course, vary from one make and/or model to another.
As said earlier, Error Code P0234 suggests the PCM senses a dangerously high boost pressure from the engine’s forced induction system. Excess boost level can compromise the engine’s structural integrity.
The Turbo Charging system is equipped with a Boost Pressure Sensor, which runs to continually send data back to the PCM. This provides the feedback loop between the requested level of turbo charger boost of the PCM and the actual level of the Turbo Charger Boost. If the pressure reading goes way over the specified pressure, or when the Knock Sensors signal that the engine is knocking, it will trigger the Error Code and activate the Check Engine light.
The most common tell-tale sign is of course, the activation of the Check Engine light. In terms of symptoms, that actually depends on the cause of the overboost condition. Some of the most common symptoms are:
- Loss of power or no turbo charger boost
- Engine overheating
- Harsh transmission or transmission overheating
- Engine knocking or pinging especially on acceleration
- Ignition misfiring
In some cases, the engine may run normally until the excessive overboost blows out a gasket or seal. In relation, the engine overboost condition may cause gasket or seals to the heads or intake to fail.
There are many reasons for this error code to appear, and as said earlier, the type and severity of the symptoms depends on the nature of the cause of the overboost condition. Some of the most common possible causes of Error Code P0234 are:
- Damaged or sticking turbo charger or supercharger wastegate
- Sticking wastegate control valve solenoid
- Blocked wastegate control hose, keeping boost pressure from being relived quickly enough
- Defective turbo charger boost sensor or actuator
- Corroded or faulty turbo charger boost sensor connectors or wirings
- Defective knock sensor(s), connections or wirings
How to Check
As with other engine trouble codes, troubleshooting for Error Code P0234 starts with scanning and documenting the freeze frame data to verify the problem.
Then, the codes shall be cleared to verify whether the problem comes back.
This is where you can check the operation of the boost pressure solenoid for proper operation of wastegate.
Check the wastegate if it’s binding or sticking.
Lastly, check the relief hose of the wastegate and look for signs of blockages, damages or kinks.
How to Fix
The most common fix for this Error Code is to replace the defective boost sensor. Defective meaning, it’s not providing the right pressure reading to the PCM.
Sticking wastegate must also be replaced.
Replacing a binding or sticking wastegate valve.
Repair of replacement of damaged wastegate lines caused by kinks or blockages.
Again, this code is triggered by the intake boost sensor, which indicates an overboost condition. Its most common failure is wastegate intermittently binding or sticking.
The pressure it causes can give the engine a lot of power; however, an overboost condition may cause engine failure, which can be a pretty serious condition, especially for engines not designed for such high pressure intake. This error code can lead to blown engine or blown head gasket.