What it means
Same as P04CE with the signal voltage below the plausible range. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
EGR temperature sensor C monitors temperature in the exhaust gas recirculation system and reports it to the control module. P04D0 sets when the sensor signal falls below the expected electrical range, commonly because the signal is shorted to ground or the circuit 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
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
How to diagnose it
- Record freeze-frame data and check scan-tool readings for EGR temperature sensor C to confirm the low input.
- With the engine cool, inspect sensor C's connector and wiring for corrosion, moisture, pushed-back pins, or chafing to ground.
- Using the wiring diagram, test the signal circuit for a short to ground and check continuity through sensor C and its harness.
- Wiggle the sensor C harness while monitoring the reading to see whether movement changes the low signal.
- Test the sensor and circuit against the manufacturer's specification before replacing a part.
Common fixes
- Dry, reconnect, or repair corroded or displaced sensor C connector terminals.
- Repair insulation where the sensor C signal wire is shorted to ground.
- Replace EGR temperature sensor C if it fails circuit testing.
- Repair a verified control-module input fault after checking the sensor and harness.
Can I keep driving?
If the warning light is steady and the engine runs normally, gentle driving may be possible, but avoid heavy load if it knocks, hesitates, or loses power. Faulty EGR feedback can raise NOx emissions and worsen drivability.
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.