What it means
A general circuit fault is detected on the EGT sensor at bank 1 sensor 3 (typically just downstream of the turbo or before the catalyst). The ECU loses thermal protection feedback for the catalyst and DPF.
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 reports the temperature at its position in the Bank 1 exhaust, often near after-treatment components. The control module monitors its electrical signal and sets P242A when it detects a circuit fault, leaving it without reliable temperature feedback for strategies such as exhaust protection or regeneration.
Common causes
Most likely first.
- Faulty exhaust gas temperature sensor
- Open or shorted sensor wiring
- Loose or corroded connector
Symptoms
- Check-engine light on
- Reduced power or limited regeneration, if enabled by the vehicle
How to diagnose it
- Record freeze-frame data and inspect live data for Bank 1 Sensor 3, checking whether its reading is missing or implausible compared with other exhaust-temperature sensors.
- With the exhaust cool, locate the Bank 1 Sensor 3 connector and inspect it and the nearby harness for heat damage, loose pins, corrosion, or chafing.
- Check the sensor circuit for opens or shorts using the manufacturer’s procedure and specifications.
- Test the Bank 1 Sensor 3 sensor itself and its connector terminals according to the manufacturer’s specification.
- After repairing the identified fault, clear the code and confirm the sensor reading responds plausibly as the exhaust warms.
Common fixes
- Reconnect or repair a loose or corroded Bank 1 Sensor 3 connector.
- Repair heat-damaged, open, or shorted sensor wiring.
- Replace a confirmed faulty Bank 1 Sensor 3 exhaust-temperature sensor.
- Repair a verified fault in the module-side circuit.
Can I keep driving?
You may be able to drive gently if the vehicle runs normally, but avoid heavy loads and monitor for reduced power or exhaust warnings. The vehicle may limit regeneration or protection functions, increasing the risk of after-treatment problems.
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.