Turbocharger/Supercharger Boost Sensor "A" Circuit Range/Performance

What it means

The turbocharger boost pressure sensor is sending a signal that is electrically valid but does not make sense compared with other sensors. The turbocharger boost pressure sensor measures the pressure the turbocharger is producing so the ECU can control boost. This usually points to a sensor that is reading wrong, or to a real mechanical problem it is reporting correctly, rather than a broken wire.

Symptoms

• Check engine light on
• Loss of power or limp mode
• Turbo not building boost
• Black smoke (diesel)

Probable causes

Most likely first

1. 1Leaking intercooler hoses or clamps
2. 2Oil-fouled sensor
3. 3Real boost control problem (wastegate or VGT vanes)
4. 4Failing sensor giving an inaccurate reading
5. 5Poor connection at the sensor connector

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the turbocharger boost pressure sensor connector and wiring (on the intake pipe after the intercooler or on the intake manifold). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the turbocharger boost pressure sensor reading on live data. With the engine off it should read close to barometric pressure. Boost should rise smoothly under load.
4. 4Compare the turbocharger boost pressure sensor reading against related sensors and the real-world condition. If they disagree, find out which one is telling the truth before buying parts.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Fix the underlying problem the sensor is reporting, if real
• Replace the turbocharger boost pressure sensor if it reads wrong against a known-good reference