What it means
Same as P04CE with the signal voltage above 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 measures temperature in the exhaust gas recirculation system for the control module. P04D1 sets when its signal rises above the expected electrical range, often because the signal is shorted to a supply voltage or a connection is faulty.
Common causes
Most likely first.
- Signal shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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 sensor C live data to confirm the input is high compared with expected conditions.
- With the engine cool, inspect sensor C's connector and harness for damaged pins, corrosion, or a signal wire pinched against a power source.
- Use the wiring diagram to test the signal circuit for a short to supply and check connector fit and continuity.
- Move the harness gently while watching the live reading to identify a movement-sensitive short or connection fault.
- If no wiring fault is found, test sensor C and the module input against the manufacturer's specification.
Common fixes
- Repair or replace corroded, damaged, or displaced sensor C connector terminals.
- Repair the signal wire where it is shorted to a supply source.
- Replace EGR temperature sensor C if it fails testing with a sound circuit.
- Repair a verified module input fault only after the sensor and wiring pass checks.
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 pings, hesitates, or loses power. Incorrect EGR feedback can increase NOx emissions and lead to rough running.
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.