What it means
Same as P242A with the signal voltage above the plausible range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The Bank 1 Sensor 3 exhaust gas temperature sensor measures exhaust temperature at its location in the Bank 1 exhaust. The control module sets P242D when the sensor signal rises above the plausible range, commonly because the signal wire is shorted to a supply or the harness contacts a powered source.
Common causes
Most likely first.
- Signal shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check-engine light on
- Reduced power or limited regeneration, if enabled by the vehicle
How to diagnose it
- Record freeze-frame data and check Bank 1 Sensor 3 live data for a reading stuck at an implausibly high value.
- With the exhaust cool, inspect the Sensor 3 harness for pinching, melted insulation, or contact with a powered wire or terminal.
- Inspect the connector for moisture, corrosion, loose terminals, or pins pushed back into the connector body.
- Test the Sensor 3 signal circuit for a short to voltage and check continuity using the manufacturer’s procedure and specifications.
- If wiring and connector tests pass, test the sensor and confirm its reading responds plausibly as the exhaust warms.
Common fixes
- Repair a signal wire shorted to a supply or pinched against a powered source.
- Clean and secure a corroded or loose Sensor 3 connector.
- Replace a confirmed faulty Bank 1 Sensor 3 sensor.
- Repair a verified module-side circuit fault.
Can I keep driving?
Drive gently and avoid towing or sustained high loads while the temperature signal is implausibly high. The module may restrict power or regeneration, and an actual overheating exhaust condition could damage after-treatment parts.
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.