Deutz-Fahr M33 – Engine ECU (EMR): Boost Pressure Sensor plausibility fault or defective sensor

The Engine Control Unit has detected that the boost pressure value is out of range or not plausible. A common trigger for this plausibility fault is that when the engine is turned off, the reading from the boost pressure sensor does not match the reading from the ambient air pressure sensor. It can also indicate that the boost pressure has exceeded the maximum threshold or the sensor's measuring range.

• Deutz-Fahr Tractors (e.g., Series 5, 5D VSF CVT T4i)
• JLG Boom Lifts

1. 1

   With the engine off, use a diagnostic tool to compare the ambient pressure sensor reading with the boost pressure sensor reading. They should be identical.

2. 2

   Check the turbocharger wastegate valve to ensure it is not mechanically blocked or stuck closed, which can cause actual overboost conditions.

3. 3

   Inspect the wiring harness between the sensor and the ECU for open circuits or short circuits to ground. Depending on your specific engine model, check the continuity at the ECU pins (e.g., pins A07, A54, A28/A29 are commonly referenced for the FARMotion/TCD engines).

4. 4

   Ensure the sensor is receiving the correct 5.0V supply voltage.

1. 1

   Safety First

   Place the machine on a flat surface, turn off the engine, remove the ignition key, and allow the machine to cool down completely.

2. 2

   Locate the Sensor

   Locate the boost pressure sensor (often a 4-pin combination sensor that also measures intake temperature) on the intake manifold after the intercooler.

3. 3

   Disconnect and Inspect

   Unplug the connector from the sensor. Inspect the connector terminals for corrosion, pushed-out pins, or moisture.

4. 4

   Repair Wiring

   If the diagnostic checks revealed an open or short circuit in the wiring harness, repair the affected wires.

5. 5

   Replace Sensor

   If the wiring is intact, the wastegate is functioning normally, and the fault code remains active (or the sensor fails the engine-off plausibility check), replace the boost pressure sensor.

6. 6

   Clear and Calibrate

   Clear the fault codes using a diagnostic tool. In some EMR systems, replacing the combination sensor may require an ECU calibration or reset procedure.