Open or broken wire in the sensor signal circuit between the EGR temperature sensor and the powertrain control module; Short to voltage on the signal circuit, often from chafed insulation against a hot exhaust component; Failed EGR temperature sensor D with an internal open circuit or skewed thermistor; Corroded or loose electrical connector at the sensor or at the PCM harness; High resistance in the sensor ground circuit, causing the signal voltage to float high; PCM internal fault on the signal input channel, which is rare but possible after other causes are ruled out

DTC codes / P04xx · Auxiliary emission controls / P04E8

P04E8EGR Temperature Sensor D Circuit High

Q: What does code P04E8 mean?

EGR Temperature Sensor D Circuit High. P04E8 means the engine computer has detected an abnormally high voltage on the signal circuit for EGR temperature sensor D, which is typically the sensor monitoring the exhaust gas recirculation cooler outlet on one bank of a V-style engine. The computer expects the sensor's signal voltage to stay within a calibrated range, and a sustained high reading tells it the circuit is open, shorted to voltage, or the sensor element has failed.

P04E8 means the engine computer has detected an abnormally high voltage on the signal circuit for EGR temperature sensor D, which is typically the sensor monitoring the exhaust gas recirculation cooler outlet on one bank of a V-style engine. The computer expects the sensor's signal voltage to stay within a calibrated range, and a sustained high reading tells it the circuit is open, shorted to voltage, or the sensor element has failed.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
A slight decrease in fuel economy if the fault affects EGR flow metering
Intermittent rough idle or hesitation when the engine is cold, if the EGR system is disabled as a result
Elevated exhaust gas temperatures or a related EGR flow code stored alongside P04E8
No drivability change at all in many cases, because the fault is confined to a sensor circuit

Common causes, most likely first

Open or broken wire in the sensor signal circuit between the EGR temperature sensor and the powertrain control module
Short to voltage on the signal circuit, often from chafed insulation against a hot exhaust component
Failed EGR temperature sensor D with an internal open circuit or skewed thermistor
Corroded or loose electrical connector at the sensor or at the PCM harness
High resistance in the sensor ground circuit, causing the signal voltage to float high
PCM internal fault on the signal input channel, which is rare but possible after other causes are ruled out

How to diagnose and fix it

Scan all modules and record freeze-frame data for P04E8, then clear the code and verify whether it returns immediately or only after a specific drive cycle
Inspect the EGR temperature sensor D connector and the harness routing for corrosion, chafing, or heat damage, and repair any damaged terminals
Measure sensor resistance with a multimeter and compare it to the expected value for the ambient or engine temperature, replacing the sensor if it is open or out of range
Back-probe the signal circuit at the PCM connector and check for a short to voltage with the sensor disconnected, repairing the harness if battery voltage is present
Check the sensor ground circuit for excessive resistance by measuring voltage drop between the sensor ground pin and battery negative
If the harness and sensor test good, substitute a known-good sensor or use a signal generator to confirm the PCM responds correctly before condemning the PCM
After repair, clear codes and run the EGR monitor to completion to confirm the fix

What a high EGR temperature signal really means

A high signal voltage on a thermistor-type EGR temperature sensor almost always means an open circuit or a disconnected sensor, not an actual overheating condition, because the resistance rises as temperature falls.
Technicians often replace the EGR temperature sensor when the real fault is a chafed signal wire near the exhaust manifold, so always wiggle-test the harness while watching live data before condemning the sensor.
On some engines, sensor D is the EGR cooler outlet sensor on bank 2, and a failed cooler can contaminate the sensor with coolant or soot, causing a high resistance reading that mimics an electrical open.
A poor ground at the sensor can push the signal voltage high on the PCM input, so a voltage-drop test on the ground circuit is just as important as checking the signal wire.
P04E8 can set intermittently from vibration or thermal cycling, and a code that only appears on cold starts often points to a connector terminal that loses contact as the harness contracts.

Can I keep driving with P04E8?

You can usually continue driving with P04E8 because the fault affects only a sensor circuit and the engine management system will default to a safe EGR strategy. Avoid long periods of heavy towing or sustained high-load operation until the circuit is repaired, since a disabled EGR system can raise combustion temperatures.

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.