CLAAS Id772Fh / 772Fh (157 03) – ENG (A15): Input voltage of the fuel pressure sensor in the common rail high

The engine control unit is receiving a voltage signal from the common rail fuel pressure sensor that exceeds the normal operating range (often caused by a short circuit to a higher voltage, an open signal circuit, or an internal sensor failure). The engine calculator automatically reduces engine power by 20% per minute until it reaches 50% of its nominal power, defaulting to a fixed 2,000 bar pressure.

• Axion 800 series
• Axion 800
• Axion 850

1. 1

   Inspect the fuel pressure sensor on the common rail (Component B42)

2. 2

   Inspect the wiring harness between the B42 sensor and the ENG (A15) module for an open circuit, disconnected plug, or short-circuit to a higher voltage source

3. 3

   Verify the connections at the ENG (A15) engine calculator

1. 1

   Visual Inspection

   Locate the fuel rail pressure sensor (B42) on the common rail. Disconnect the sensor plug and inspect the pins for corrosion, moisture, or pushed-back terminals.

2. 2

   Circuit Testing

   Using a multimeter, verify the reference voltage and ground at the sensor connector with the key on. Check the signal wire for continuity back to the ENG (A15) ECU and ensure it is not shorted to power.

3. 3

   Sensor Replacement

   If the wiring harness tests good and the connector is secure, the sensor itself has failed internally (voltage out of range high) and must be replaced.

4. 4

   Clear and Verify

   After replacing the sensor, clear the fault codes from the ENG (A15) module. Start the engine and verify that the 50% power derate is lifted and the code does not return.