Damaged, corroded or loose connector at the EGR temperature sensor; Open circuit or high resistance in the sensor signal or ground wire; Faulty EGR temperature sensor (internal open circuit or drift); Signal wire shorted to a voltage supply; Heat or exhaust damage to wiring near the EGR cooler or pipework; Fault in the engine control unit sensor input or supply.

P04E8

EGR Temperature Sensor D Circuit High.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
E8: FaultThe specific fault in that area

What it means

P04E8 means the engine control unit has seen the signal from EGR temperature sensor 'D' sitting higher than the expected range, which indicates a high-voltage circuit fault. These sensors are usually thermistors, so an open circuit, a poor connection or a short to voltage can look like a very cold reading. Which sensor is 'D', and where it sits in the EGR system, depends on the make, model and engine.

Symptoms

Engine management light on
EGR system monitor not completing or other EGR codes stored alongside
Possible rough running or hesitation if the EGR system is being limited
Slightly higher emissions or poorer economy
Possible reduced power if the control unit enters a limited operating strategy

Possible causes

Damaged, corroded or loose connector at the EGR temperature sensorlikely
Open circuit or high resistance in the sensor signal or ground wirelikely
Faulty EGR temperature sensor (internal open circuit or drift)likely
Signal wire shorted to a voltage supplypossible
Heat or exhaust damage to wiring near the EGR cooler or pipeworkpossible
Fault in the engine control unit sensor input or supplyrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine temperature, load and speed when the fault set
Check for related EGR, intake or exhaust temperature codes and for any manufacturer service bulletins for the model and engine
Inspect the sensor, wiring and connector for heat damage, chafing, corrosion, water ingress or a loose pin
View live data for sensor 'D' temperature and voltage with the engine cold, then compare it with other temperature sensors on the same engine
Unplug the sensor and measure its resistance against the manufacturer's specification at a known temperature
With the connector unplugged and the ignition on, check the reference voltage, then check the signal and ground wires for continuity, and for shorts to voltage or earth
Wiggle-test the harness while watching live data for dropouts or jumps
Check the reading again after repair, and confirm the EGR system operates normally

How to fix

Clean, repair or replace a corroded or damaged connector and terminals
Repair or replace open or shorted wiring, and secure it away from heat sources
Replace the EGR temperature sensor if it is out of specification or reads incorrectly
Replace the wiring section or harness if heat has damaged it
Replace or repair the control unit only after all wiring and sensor faults are ruled out and the fault is confirmed

Can I keep driving?

Low severity

The car can usually be driven short-term while you arrange a repair, as this is a sensor circuit fault. If the car loses power, runs roughly or has other warning lights, have it checked sooner.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.