P04D1

What it means

P04D1 means the engine control unit has detected a high voltage signal from EGR temperature sensor 'C' circuit, above the expected range. This usually points to an open circuit, a short to voltage or a failed sensor. Which EGR cooler or passage sensor 'C' refers to depends on the vehicle and engine, so check the manufacturer's information.

Symptoms

• Engine warning light on
• Possible reduced performance or limp mode on some vehicles
• Rough idle or hesitation on some engines
• Increased exhaust emissions or failed emissions test
• Other EGR-related codes stored alongside

Possible causes

• Damaged, corroded or loose connector at the EGR temperature sensorlikely
• Open circuit or high resistance in the signal or ground wire to the sensorlikely
• Failed EGR temperature sensorlikely
• Signal wire shorted to a voltage supplypossible
• Heat or physical damage to the wiring near the EGR cooler or exhaustpossible
• Fault inside the engine control unitrare

How to diagnose

1. Read all stored codes and freeze frame data, noting engine temperature and load when the fault set, and look for other EGR or sensor supply codes
2. Identify the location of EGR temperature sensor C for this model and engine using manufacturer data
3. Inspect the sensor, connector and wiring for heat damage, chafing, corrosion, moisture or bent pins
4. View the live EGR temperature reading with the engine cold; it should be close to ambient or coolant temperature, and a reading stuck at maximum suggests an open circuit or short
5. Unplug the sensor and check the live value and the voltage at the connector against specification, as a reading that changes shows the fault is in the sensor or its circuit
6. Measure sensor resistance and compare with the manufacturer's values at a known temperature
7. Check the signal and ground wires for continuity and for shorts to voltage or ground
8. Check the reference voltage and ground at the control unit connector before suspecting the unit

How to fix

• Clean, repair or replace the damaged connector or terminals
• Repair or replace the damaged or open-circuit wiring
• Replace the EGR temperature sensor if it is out of specification
• Repair any short to voltage in the signal wire
• Replace the control unit only after all wiring and sensor faults are ruled out, and follow any required programming procedure
• Clear the codes after repair and road test to confirm the fault does not return

Can I keep driving?

Nearby codes

• P04D0GenericEGR Temperature Sensor C Circuit Low
• P04D2GenericEGR Temperature Sensor C Circuit Intermittent/Erratic