P0474 signals that the exhaust pressure sensor's electrical circuit is intermittently erratic, causing the PCM to receive irregular pressure readings.
The sensor can develop internal faults that cause its signal to drop out or fluctuate intermittently.
Poor contact at the connector can interrupt the signal, especially when the vehicle vibrates.
Chafed, broken, or exposed wires can create intermittent opens or shorts in the circuit.
A PCM failure can cause spurious circuit faults, but this is uncommon and should be considered only after other causes are ruled out.
A severe blockage (e.g., clogged diesel particulate filter) can cause abnormal pressure that appears erratic to the sensor.
Replacing the PCM is rarely necessary; the issue is usually a faulty sensor, wiring, or connector rather than a control‑module failure.
A severe blockage can affect exhaust pressure readings, but the code most often points to a sensor or circuit problem rather than the exhaust itself.
No, the exhaust pressure sensor measures pressure in the exhaust stream, typically downstream of the turbine, and is distinct from boost pressure sensors.
Keep the connector clean and protected from moisture, inspect wiring for wear, and address any exhaust restrictions promptly.