Faulty EGR temperature sensor sending an incorrect high signal.; Shorted or chafed wiring in the sensor signal circuit touching a voltage source.; Corroded or damaged electrical connector at the sensor or ECM.; Failed engine control module (ECM) driver for the sensor circuit.; Excessive carbon buildup on the sensor tip causing abnormal readings.; Aftermarket or incorrect sensor installed previously.

DTC codes / Volkswagen codes / P1408

P1408 · VolkswagenEGR Temperature Sensor Signal Too High

Q: What does code P1408 mean?

EGR Temperature Sensor Signal Too High. P1408 on Volkswagen vehicles means the engine control module has detected an excessively high voltage from the exhaust gas recirculation temperature sensor, indicating the sensor signal is out of range or the circuit is shorted to voltage. The computer expects a specific voltage range that corresponds to the EGR gas temperature, and a signal above the upper limit triggers this code.

P1408 on Volkswagen vehicles means the engine control module has detected an excessively high voltage from the exhaust gas recirculation temperature sensor, indicating the sensor signal is out of range or the circuit is shorted to voltage. The computer expects a specific voltage range that corresponds to the EGR gas temperature, and a signal above the upper limit triggers this code.

SystemPowertrain

Code typeVolkswagen specific

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms.
Slightly rough idle or hesitation during acceleration in some cases.
Reduced fuel economy if the EGR system is disabled by the ECM.
Intermittent misfire or stumbling under light throttle.
Failed emissions test due to increased nitrogen oxide output.
In rare cases, a noticeable decrease in engine power.

Common causes, most likely first

Faulty EGR temperature sensor sending an incorrect high signal.
Shorted or chafed wiring in the sensor signal circuit touching a voltage source.
Corroded or damaged electrical connector at the sensor or ECM.
Failed engine control module (ECM) driver for the sensor circuit.
Excessive carbon buildup on the sensor tip causing abnormal readings.
Aftermarket or incorrect sensor installed previously.

How to diagnose and fix it

Connect a scan tool and verify P1408 is active, then check freeze frame data for sensor voltage.
Visually inspect the EGR temperature sensor connector and wiring for damage, corrosion, or chafing.
Measure sensor resistance and compare to Volkswagen specifications for the current temperature.
Backprobe the sensor signal wire at the ECM and check for a short to voltage with the key on.
If wiring is intact, replace the EGR temperature sensor with a genuine or OEM-equivalent part.
Clear the code and perform a road test to confirm the repair and ensure the monitor runs.
If the code returns, diagnose the ECM circuit or replace the ECM as a last resort.

Don't overlook the wiring harness

A shorted signal wire often causes this code, and the harness near the EGR pipe is a common chafe point due to heat and vibration.
The EGR temperature sensor on many Volkswagen engines is integrated into the EGR cooler or valve assembly, making replacement more involved than a standalone sensor.
Carbon buildup on the sensor tip can skew readings high without any electrical fault, so cleaning the sensor may resolve the issue before replacement.
This code can be set by a faulty ECM driver that applies voltage to the signal circuit, which is often misdiagnosed as a sensor failure.
After replacing the sensor, the ECM may need a adaptation reset or a driving cycle to relearn the EGR temperature range.

Can I keep driving with P1408?

You can generally continue driving with P1408, but avoid prolonged idling and heavy acceleration until the fault is repaired. If the check engine light starts flashing or you notice performance issues, have the vehicle inspected promptly.

Tools that help

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Guidance is general and written for Volkswagen vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.