Faulty EGR temperature sensor (sensor element degraded or open circuit); Carbon buildup or soot contamination on the sensor tip, insulating it from exhaust gas flow; Damaged or corroded wiring harness connector at the sensor; Failed EGR valve stuck closed or partially open, preventing expected temperature changes; Exhaust leaks before the EGR temperature sensor causing inaccurate readings; ECU software issue or faulty ECU (rare, but possible on older models)

DTC codes / Volkswagen codes / P1406

P1406 · VolkswagenEGR Temperature Sensor Range Performance

Q: What does code P1406 mean?

EGR Temperature Sensor Range Performance. P1406 on Volkswagen vehicles indicates that the engine control module has detected an out-of-range performance from the exhaust gas recirculation temperature sensor, which is used to monitor the temperature of the recirculated exhaust gas. The sensor's signal does not correlate with expected values under the operating conditions the ECU is commanding, often after the engine has reached operating temperature and the EGR system is active.

P1406 on Volkswagen vehicles indicates that the engine control module has detected an out-of-range performance from the exhaust gas recirculation temperature sensor, which is used to monitor the temperature of the recirculated exhaust gas. The sensor's signal does not correlate with expected values under the operating conditions the ECU is commanding, often after the engine has reached operating temperature and the EGR system is active.

SystemPowertrain

Code typeVolkswagen specific

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Slightly rough idle or hesitation during light acceleration when the EGR valve opens
Reduced fuel economy as the ECU may alter injection timing to compensate
In rare cases, a slight increase in engine temperature if the EGR system is disabled by the ECU
Intermittent fault code setting during steady-speed driving when EGR is active

Common causes, most likely first

Faulty EGR temperature sensor (sensor element degraded or open circuit)
Carbon buildup or soot contamination on the sensor tip, insulating it from exhaust gas flow
Damaged or corroded wiring harness connector at the sensor
Failed EGR valve stuck closed or partially open, preventing expected temperature changes
Exhaust leaks before the EGR temperature sensor causing inaccurate readings
ECU software issue or faulty ECU (rare, but possible on older models)

How to diagnose and fix it

Use a scan tool to read live data from the EGR temperature sensor and compare it to ambient and coolant temperature after a cold start
Visually inspect the sensor and its connector for corrosion, damage, or loose pins; clean or repair as needed
Remove the EGR temperature sensor and check for heavy carbon deposits; clean the sensor tip with appropriate solvent if contaminated
Test the sensor's resistance with a multimeter across a range of temperatures and compare to Volkswagen specifications
Check the EGR valve operation with a scan tool bidirectional test and inspect for carbon sticking; clean or replace if faulty
Verify that the ECU has the latest software calibration and update if required
Replace the EGR temperature sensor if all wiring and mechanical checks pass but the signal remains implausible

Don't overlook the EGR valve itself

A sticking EGR valve often causes P1406 because the temperature sensor never sees the expected temperature change when the valve is commanded open, even though the sensor itself is fine.
Carbon fouling on the sensor tip is common on higher-mileage Volkswagen engines and can be cleaned rather than replaced, saving unnecessary part costs.
The EGR temperature sensor on many VW engines is located in a difficult-to-reach spot on the EGR pipe, so a faulty reading can sometimes be caused by a poor connection rather than a failed sensor.
P1406 can be set by an exhaust leak upstream of the sensor, which dilutes the exhaust gas and lowers the measured temperature, mimicking a sensor fault.
On some models, a weak battery or charging system issue can cause intermittent sensor codes; always check system voltage before condemning the sensor.

Can I keep driving with P1406?

The vehicle is generally safe to drive with P1406 because the fault primarily affects emissions and fuel economy, not immediate engine safety. Avoid prolonged heavy acceleration or towing until the fault is repaired, as the EGR system may be disabled and engine knock could occur under load.

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.