Code U0690 indicates that the engine control module has lost communication with the EGR Temperature Sensor D. This means the computer is not receiving the expected data signal from the sensor, preventing it from monitoring the temperature of the recirculated exhaust gases.
Frayed, burnt, or corroded wiring between the sensor and the PCM, often caused by extreme engine bay heat.
Internal electronic failure of the sensor itself, preventing it from transmitting data.
Loose, corroded, or backed-out pins at the sensor connector or the PCM harness.
A blown fuse in the circuit providing power to the sensor or the associated communication network.
Internal failure of the engine control module's communication circuitry.
Usually no. While the PCM is a potential cause, U-codes are most frequently caused by wiring degradation or sensor failure due to the harsh environment of the exhaust system.
The vehicle is typically drivable, but the engine may enter a reduced-power mode to protect the system, and it will not pass an emissions test.
Many modern engines use multiple EGR temperature sensors to monitor different stages of the recirculation process; 'D' simply identifies which specific sensor in the sequence is failing to communicate.