Failed exhaust gas temperature sensor (internal short to ground); Damaged or chafed sensor wiring shorting to ground; Corroded or loose electrical connector at the sensor; Open or shorted sensor return circuit; Faulty engine control module (rare but possible); Exhaust system modifications or leaks affecting sensor readings

DTC codes / P24xx · Auxiliary emission controls / P242C

P242CExhaust Gas Temperature Sensor Circuit Low Bank 1 Sensor 3

Q: What does code P242C mean?

Exhaust Gas Temperature Sensor Circuit Low Bank 1 Sensor 3. P242C means the engine control module has detected an abnormally low voltage signal from the exhaust gas temperature sensor located after the diesel particulate filter on bank 1, sensor 3. The computer expects a voltage within a specific range that corresponds to the exhaust temperature, and a low reading indicates the circuit is shorted to ground or the sensor has failed.

P242C means the engine control module has detected an abnormally low voltage signal from the exhaust gas temperature sensor located after the diesel particulate filter on bank 1, sensor 3. The computer expects a voltage within a specific range that corresponds to the exhaust temperature, and a low reading indicates the circuit is shorted to ground or the sensor has failed.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Reduced engine power or limp mode if the ECM derates the engine to protect the aftertreatment system
Increased diesel particulate filter regeneration frequency or inability to complete a regeneration
Poor fuel economy as the ECM adjusts fueling based on faulty temperature data
Possible black smoke or excessive exhaust odor if regeneration is inhibited
In some cases, the vehicle may enter a forced idle or shutdown strategy

Common causes, most likely first

Failed exhaust gas temperature sensor (internal short to ground)
Damaged or chafed sensor wiring shorting to ground
Corroded or loose electrical connector at the sensor
Open or shorted sensor return circuit
Faulty engine control module (rare but possible)
Exhaust system modifications or leaks affecting sensor readings

How to diagnose and fix it

Scan all modules and record freeze-frame data to confirm the fault is current and not intermittent
Visually inspect the sensor, connector, and wiring for damage, corrosion, or chafing
Measure sensor resistance and compare to manufacturer specifications
Backprobe the sensor signal circuit to check for a short to ground with the key on
Check the sensor reference voltage and ground circuit integrity
Replace the exhaust gas temperature sensor if resistance is out of specification
Clear codes and perform a road test to verify the repair and ensure no pending codes return

What most technicians overlook on P242C

A low voltage code often results from a short to ground in the wiring harness rather than a failed sensor, so always inspect the harness routing near hot or moving components.
The ECM may set P242C as a companion code when a DPF regeneration is interrupted, and the sensor itself may be fine once the regeneration completes.
Some aftermarket exhaust systems or sensor spacers can cause incorrect temperature readings that trigger this code even with a good sensor.
A faulty sensor can cause the ECM to command excessive regeneration, leading to DPF damage if left unresolved.
Always check for related codes such as P242A or P242B to determine if the fault is specific to sensor 3 or affects multiple sensors.

Can I keep driving with P242C?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy loads or long trips because the ECM may inhibit DPF regeneration and cause further damage. If the engine enters limp mode, seek service immediately.

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.