Faulty exhaust gas temperature sensor (bank 1 sensor 3) due to age or contamination; Damaged or corroded wiring harness or connector at the sensor; Exhaust leaks near the sensor causing inaccurate temperature readings; Failed sensor heating element or internal short in the sensor; Powertrain control module software issue or outdated calibration; Restricted exhaust flow or damaged substrate in the diesel particulate filter or catalytic converter

DTC codes / P24xx · Auxiliary emission controls / P242B

P242BExhaust Gas Temperature Sensor Circuit Range or Performance Bank 1 Sensor 3

P242B indicates that the powertrain control module has detected an out-of-range or performance problem with the exhaust gas temperature sensor circuit for bank 1 sensor 3, which is typically the sensor after the diesel particulate filter or catalytic converter. The computer compares the sensor signal against expected values during specific operating conditions and sets the code when the voltage or temperature reading falls outside the programmed limits.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine power or limp mode in some vehicles
Poor fuel economy or increased regeneration frequency for diesel particulate filters
Intermittent rough running or hesitation during acceleration
A message on the dashboard indicating exhaust system service required

Common causes, most likely first

Faulty exhaust gas temperature sensor (bank 1 sensor 3) due to age or contamination
Damaged or corroded wiring harness or connector at the sensor
Exhaust leaks near the sensor causing inaccurate temperature readings
Failed sensor heating element or internal short in the sensor
Powertrain control module software issue or outdated calibration
Restricted exhaust flow or damaged substrate in the diesel particulate filter or catalytic converter

How to diagnose and fix it

Perform a visual inspection of the sensor, wiring, and connector for damage, corrosion, or loose connections
Use a scan tool to check live data for the bank 1 sensor 3 temperature reading and compare it to ambient and expected values after a cold start
Check the sensor's resistance and voltage output according to the manufacturer's specifications
Inspect the exhaust system for leaks or restrictions upstream of the sensor
Test the sensor circuit for continuity, shorts to ground, and shorts to power using a multimeter
Replace the exhaust gas temperature sensor if it fails electrical or performance tests
Clear the diagnostic trouble codes and perform a road test to verify the repair and ensure the code does not return

Key checks before replacing the EGT sensor

A common misdiagnosis is replacing the sensor when the real problem is a corroded connector or chafed wire that intermittently shorts, so always wiggle-test the harness while watching live data.
Exhaust leaks upstream of the sensor can cause it to read lower than actual temperature, setting a range code without any sensor fault, so inspect for soot trails around joints and gaskets.
On many diesel vehicles, sensor 3 is the post-DPF sensor, and its readings are critical for regeneration strategy; a lazy sensor may not set a code until regeneration is commanded.
The code can be set by a faulty thermostat or cooling system issue that prevents the engine from reaching normal operating temperature, skewing the expected temperature model.
After replacing the sensor, some vehicles require a relearn or adaptation reset for the new sensor to be recognized properly, so consult the service information for the specific model.

Can I keep driving with P242B?

You can generally continue driving with this code if the engine runs normally, but avoid long trips or heavy loads until it is diagnosed. If the vehicle enters limp mode or you notice excessive smoke or power loss, have it inspected promptly to prevent damage to the emissions system.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.