Damaged, chafed, or corroded wiring in the sensor circuit, especially near hot exhaust components; Loose or contaminated electrical connector at the sensor or at the powertrain control module; Failed cylinder head temperature sensor B itself, due to age or heat exposure; High resistance in the ground circuit for the sensor; Internal fault in the powertrain control module affecting the sensor input; Aftermarket or incorrect sensor installed previously with wrong resistance characteristics

DTC codes / P2Cxx · Hybrid propulsion / P2C38

P2C38Cylinder Head Temperature Sensor B Circuit

Q: What does code P2C38 mean?

Cylinder Head Temperature Sensor B Circuit. P2C38 indicates that the powertrain control module has detected an electrical fault in the circuit for Cylinder Head Temperature Sensor B, which is a second temperature sensor used on some engines to monitor head temperature independently. The computer compares the sensor signal against expected values and flags the code when the voltage or resistance falls outside the normal range, often due to a wiring or connection problem rather than a failed sensor.

P2C38 indicates that the powertrain control module has detected an electrical fault in the circuit for Cylinder Head Temperature Sensor B, which is a second temperature sensor used on some engines to monitor head temperature independently. The computer compares the sensor signal against expected values and flags the code when the voltage or resistance falls outside the normal range, often due to a wiring or connection problem rather than a failed sensor.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Rough running or misfire when the engine is cold or overheating
Poor fuel economy or altered engine performance as the computer substitutes a default temperature value
Incorrect or erratic temperature gauge readings on the dashboard
Possible reduced engine power or limp mode in some vehicles
Fan running constantly or not engaging when needed due to faulty temperature data

Common causes, most likely first

Damaged, chafed, or corroded wiring in the sensor circuit, especially near hot exhaust components
Loose or contaminated electrical connector at the sensor or at the powertrain control module
Failed cylinder head temperature sensor B itself, due to age or heat exposure
High resistance in the ground circuit for the sensor
Internal fault in the powertrain control module affecting the sensor input
Aftermarket or incorrect sensor installed previously with wrong resistance characteristics

How to diagnose and fix it

Use a scan tool to read live data for cylinder head temperature sensor B and compare it to ambient and engine temperature after a cold soak
Visually inspect the sensor, connector, and wiring harness for damage, corrosion, or loose pins, repairing as needed
Measure resistance across the sensor terminals and compare to the manufacturer's specification for the current temperature
Check the sensor reference voltage and ground circuit integrity with a multimeter, looking for opens or shorts
If wiring and sensor test good, substitute a known-good sensor to see if the code returns
Clear the code and perform a road test with the scan tool recording to confirm the repair
If the fault persists after all circuit checks, diagnose the powertrain control module or seek dealer-level programming

Don't overlook the wiring harness first

A common mistake is replacing the cylinder head temperature sensor B without checking the harness, since heat and vibration often damage the wires long before the sensor fails.
This code can set intermittently due to a poor connection that only acts up when the engine is hot or during certain driving conditions, so a wiggle test of the harness while watching live data is valuable.
Some vehicles use cylinder head temperature sensor B primarily for monitoring and may not trigger noticeable symptoms, leading owners to ignore the code until a secondary fault develops.
The sensor's resistance curve is temperature-dependent, so testing it at room temperature alone is not enough; you must compare readings at multiple temperatures or use a scan tool to verify the signal.
A faulty thermostat or cooling system issue can cause the sensor to read out of range and set this code, so always verify actual engine temperature with an infrared thermometer before condemning the sensor.

Can I keep driving with P2C38?

You can usually continue driving with this code if the engine temperature gauge reads normally and there are no drivability symptoms, but avoid heavy loads or long trips until it is repaired. If the engine overheats or runs poorly, stop driving and have it diagnosed promptly to prevent damage.

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.