P04E8: EGR Temperature Sensor D Circuit High

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. Sensor D is the fourth of up to four EGR temperature sensors, conceivable on engines with high- and low-pressure EGR and a sensor before and after each cooler; it is usually an NTC whose low voltage means hot. No manufacturer document available to us uses sensor D; the description follows CARB and Ford's checks on sensor B as a comparison. P04E8 means the signal is above its upper limit – an open circuit in sensor, connector, line or ground, or a short to positive; the reading looks very cold. For sensor B Ford uses above 4.95 V. A substitute value is used.

Medium severity. Can I keep driving?You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.

Symptoms

Check engine light on
Usually no change in driving
EGR possibly reduced, higher NOx

Most likely causes

Connector off or loose, or pin corroded
Sensor open internally (heat damage)
Sensor ground line open
Signal line shorted to positive

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and any vacuum hoses
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Use live data to compare the commanded opening with the actual opening
Clean the valve and passages if they are clogged with carbon
Test the actuator with the scanner
Replace the valve if it still does not follow the command after cleaning

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P04E8 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
4: Emissions
E8: Specific fault in that system

Frequently asked questions

Can I keep driving with code P04E8?

You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.

What causes code P04E8?

The most common causes are: connector off or loose, or pin corroded; sensor open internally (heat damage); sensor ground line open.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.