What does it mean?
The turbocharger outlet pressure sensor works from a reference voltage supplied by the module and returns a signal that rises with boost pressure. This code is stored when that signal falls below the minimum voltage a working sensor can produce, usually a few tenths of a volt, and stays there for the calibrated time. Since even at rest the sensor should report atmospheric pressure and a corresponding voltage, a signal near zero cannot be a real measurement. The module treats it as a circuit fault, ignores the input and normally limits boost while the code is present.
Symptoms
- MIL on and a clear reduction in power under load
- Boost pressure value on a scan tool sitting at or near zero even with the key on and engine off
- limp mode on many vehicles because the boost feedback is unusable
- Sluggish response and poor pulling power on hills or when overtaking
- Uneven running and smoke on diesels as fuelling no longer matches real airflow
- Fault returning immediately after being cleared if the short is permanent
Likely causes
- Signal wire shorted to ground where the insulation has chafed or melted near hot components
- Internally shorted pressure sensor
- Missing reference voltage, which drops the signal to near zero even with a good sensor
- Water or corrosion in the connector bridging the signal and ground terminals
- Bent or bridged terminals inside the connector housing
- Harness pinched during charge air pipe or turbocharger service
- Rarely, a shorted input inside the control module
How to fix it
- Check the reading with the key on and engine off; a healthy sensor shows barometric pressure, not zero
- Unplug the sensor with the key on and read the signal terminal: a rise toward reference indicates a shorted sensor, a value that stays low indicates a shorted harness
- Measure reference voltage at the connector, since a lost reference imitates a low signal
- With the module connector disconnected, check resistance from the signal wire to ground to locate the short
- Inspect the connector and the harness for water, corrosion, melted insulation and crush damage
- Repair the shorted section, protect it from heat and secure it clear of moving parts
- Fit a new sensor only when the harness proves good and the sensor alone holds the signal low