What it means
The ECM detects a circuit low fault on the turbocharger/supercharger b temperature sensor. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The turbocharger/supercharger B temperature sensor reports temperature to the engine control module (ECM). The ECM monitors its signal circuit and sets P2B90 when the signal is lower than the usable range, so the reported temperature cannot be trusted for control.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
How to diagnose it
- Record freeze-frame data and compare the B sensor reading with other available temperature readings before starting and as the engine warms to see when the signal goes implausibly low.
- Inspect the B sensor connector and harness for corrosion, moisture, damaged insulation, or a signal wire touching ground.
- Check the connector terminals for corrosion or poor contact that could affect the signal, and repair any damaged terminals.
- With the wiring diagram, check the B sensor signal circuit for a short to ground and inspect its reference and ground circuits.
- Test the B sensor against the manufacturer's specification; replace it if it is internally shorted and the wiring checks out.
Common fixes
- Clean or repair corroded terminals at the B temperature sensor connector.
- Repair a B sensor signal wire shorted to ground.
- Replace the turbocharger/supercharger B temperature sensor if it fails testing.
Can I keep driving?
With only the check-engine light and no drivability symptoms, a short, gentle trip may be possible, but avoid heavy boost or towing until diagnosed. The ECM may not be able to use the B temperature reading reliably, which can affect engine control and emissions.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.