What it means
Same as P242A with the signal voltage below 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 P242C when this sensor’s signal falls below the plausible range, commonly because the signal wire is shorted to ground or the connector has a poor connection.
Common causes
Most likely first.
- Signal shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
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 low value.
- With the exhaust cool, inspect the Sensor 3 harness for chafing, melted insulation, or contact with grounded metal near the exhaust.
- Check the connector for moisture, corrosion, loose terminals, or a pin pushed back into the connector body.
- Test the Sensor 3 signal circuit for a short to ground and check continuity using the manufacturer’s procedure and specifications.
- If wiring and connector tests pass, test the sensor and verify its reading changes plausibly as the exhaust warms.
Common fixes
- Repair a signal wire shorted to ground or rubbed through against metal.
- Clean and secure a corroded, wet, 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 heavy loads if the vehicle has reduced power or an exhaust warning. The low signal can leave the module without reliable temperature feedback and may limit regeneration or exhaust protection.
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.