This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
P0235 is an OBD-II Code refers to Turbocharger Boost Sensor A Circuit Malfunction. This means the engine computer has detected a fault with the turbo boost sensor.
A P0235 code is the result of the ECM (Engine Control Module) receiving a signal indicating a problem with the turbo boost sensor (located on the turbocharger). This is a critical sensor as it lets the engine know how much boost pressure to provide based on throttle position and other factors. When the sensor goes out, the car will run poorly or not at all depending on how bad it is. The ECM may also activate a check engine light via P0340 – Turbo/Super Charger Boost Sensor A Circuit Low Input.
Common causes for this code include:
- The turbo boost pressure sensor A takes a long time to respond to changes in pressure.
- The turbo boost sensor and the MAP sensor do not produce the same reading when the engine is off and when the key is on
- The turbo boost pressure sensor A is damaged or obstructed.
The symptoms of a P0235 code are:
- The engine will lack power as the engine turbo boost may be turned off by the ECM
- The Check Engine Light will light up and the P0235 code set in ECM memory
- The engine may not receive some power during acceleration if the boost sensor is failing to register the right amount of boost pressure
To diagnose a P0235 DTC code, an automotive technician would:
1. Verify the trouble code is present using a scan tool
2. Inspect for any damage to air intake or turbocharger components that may interfere with the proper operation of the boost sensor A
3. Check the wiring harness from the IAT (Intake Air Temperature) sensor and make sure there are no breaks in it
4. Check for a blockage in the sensor port or boost sensor connector for loose or rusted pins on the turbo boost sensor.
4. Inspect for other possible engine codes such as P0340 – Turbo/Super Charger Boost Sensor Circuit Low Input, P0128 – Coolant Temperature Below Thermostat Regulating Temperature, or P0135 – O2 Sensor Heater Circuit Malfunction as these may indicate a failed turbo boost pressure sensor A as well as potentially others
5. If everything checks out okay then the turbo boost pressure sensor A is likely faulty and should be replaced.
The following are common mistakes when diagnosing the trouble code P0235:
- Fail to check for proper voltage at the turbo boost sensor A connector
- Not verifying that the boost pressure sensor hose is clear of obstructions or kinks, and not double-checking that the connections to the sensor are tight and free of leaks or kinks
- Relying on OBD-II codes alone to diagnose a problem especially on modern vehicles with multiple controllers. While your car may have hundreds of sensors, you should consider checking them all (even if not listed) as data is shared between modules and one faulty or dirty sensor can make other downstream sensors act up. Also, do not neglect the basics of engine performance such as spark plugs, ignition coils, etc.
- Not using factory diagnostic tools like OEM scan tools or data readers manufactured by Snap-on (J2534), Actron (ScanXL), Link (GST Pro), or equivalent that allow access to engine controller modes needed to read live data which allows for
How serious is this?
A car with a P0235 trouble code is not drivable and should be repaired as soon as possible. Swapping out the turbo boost pressure sensor A with a new one is recommended before installing a high-performance tune so that the ECM does not have to fight against the incorrect readings from the faulty sensor. If left unchecked, this can damage or shorten the life of components of your vehicle's performance system such as an aftermarket supercharger or turbocharger.
What repairs can fix the code?
The following are solutions that may fix this problem:
- Replace the turbo boost pressure sensor A with a working part
- Replace the faulty wiring harness from the IAT (Intake Air Temperature) sensor to the turbo boost pressure sensor A or replace it entirely as it may be corroded or broken
- Repair any blockage in the sensor port or boost pressure sensor connector for loose or rusted pins on the turbo boost pressure sensor A. While this is unlikely since these components were factory sealed, it cannot hurt to check
- If there are no other engine codes then you can try removing and reseating all of the sensors that connect to your vehicle's controller. This includes connectors for speed sensors, throttle position sensors, crankshaft position sensors, MAP/F/BARO/
A P0235 is related to and may be accompanied by the following codes:
- P0128 – Coolant Temperature Below Thermostat Regulating Temperature
- P0340 – Turbo/Super Charger Boost Sensor Circuit Low Input
- P0135 – O2 Sensor Heater Circuit Malfunction
- P0236 – Turbo/Super Charger Boost Sensor A Circuit High Input
How much does it cost to fix the P0235 code?
The repair cost of a P0235 code can vary depending on the type of repair, how it is diagnosed, and where you are located in the world. The cost may range from $100-$400 to replace a sensor with a new one. If you have an aftermarket performance system or turbocharger installed then it would be wise to check for any other engine codes before installing a high-performance tune so that the ECM does not have to fight against incorrect readings from the faulty sensor.
In conclusion, the P0235 is a trouble code that points to a problem with turbo boost pressure sensor A on the vehicle. This trouble code should be diagnosed as soon as possible and repaired ASAP. This is because of the damage an incorrect reading from faulty or dirty sensors can do to your car's performance system such as a high-performance tune, upgraded intake manifolds, aftermarket supercharger or turbocharger.
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