The U0654 code signals that the vehicle’s engine control module has lost communication with the diesel intake air flow position sensor. This sensor monitors the amount of air entering the intake manifold and its signal is essential for proper fuel metering and emissions control.
The sensor itself can fail due to internal wear, damaged contacts, or contamination, causing intermittent or lost signal.
Wiring harness or the sensor connector may be corroded, pinched, or broken, interrupting the signal path.
A vacuum leak or blockage upstream of the sensor can alter airflow readings, leading to communication loss.
In rare cases a software fault in the engine control module may misinterpret sensor data or fail to request it.
Replacing the PCM is usually unnecessary and rarely correct; the problem is almost always with the sensor or its wiring.
Yes, the intake air flow sensor is part of the emissions control system, and a loss of signal can trigger the check‑engine light.
The engine may run, but performance and fuel economy can be affected, and it may eventually trigger further diagnostic trouble codes.