What does it mean?
This code means the B turbocharger outlet pressure sensor signal has stayed above the highest voltage the module treats as valid, usually close to the five volt reference itself. A pressure sensor is designed so that a lost ground or a signal wire touching a supply voltage drives the output to the top of the scale, which the software recognises as an electrical fault rather than an enormous boost figure. The check runs continuously, including with the engine off, so the code frequently appears the moment the key is turned on. While it is present the module ignores the sensor, uses a substitute value and holds boost well below normal. The result is a clear loss of power together with the warning light.
Symptoms
- MIL on with reduced power and often limp mode
- Very high or maximum boost value shown in live data even with the engine stopped
- Poor acceleration and a flat feeling under load
- Occasional harsh transmission behaviour, because gear shift strategy uses the load signal
- Higher fuel consumption and, on diesels, smoke under load
Likely causes
- Open or high-resistance sensor ground, which lets the output float up to reference voltage
- Signal wire shorted to the five volt reference or to battery voltage inside a damaged connector or a chafed loom
- Corrosion inside the connector bridging the signal and reference pins
- Internally failed sensor stuck at maximum output
- Damaged loom after work on the intercooler, charge pipes or turbocharger
- Water leaking into the connector and creating a conductive path
- Faulty module connector or an internal fault in the control unit, considered only after the harness is proven
How to fix it
- Check the live reading with the key on and the engine off; a value at full scale with no engine running proves the signal is not coming from real pressure
- Unplug the sensor with the key on; if the module still shows maximum voltage, the signal wire is being fed from elsewhere
- Measure the sensor ground for continuity and voltage drop back to the module
- Test the signal wire for a short to the five volt reference and to battery voltage
- Inspect the connector closely for corrosion, moisture, bent pins and melted plastic
- Repair the ground or signal circuit, or replace the sensor if it is proven to be stuck high
- Clear the code, then verify the reading equals barometric pressure at key-on and follows boost during a road test