Case IH P34 – Engine Control Unit (ENG / ECU) or Powertrain Control Unit (PCU): Boost Air Pressure Sensor, Shorted To High Source

The control module is receiving an abnormally high voltage signal from the Boost Air Pressure Sensor (MAP sensor), indicating the signal wire is shorted directly to a high voltage source or the internal circuitry of the sensor has failed. As a result, the ECU reads an implausibly high turbo boost pressure.

• MXM
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190
• Maxxum Series (110 through 140)
• MXU Series
• Puma Series
• SR130
• SR150
• SR160
• SR175
• SV185

1. 1

   Inspect the wiring harness leading to the Boost Air Pressure Sensor for chafed insulation, melted wires, or pinch points where the signal wire might be shorting against a power wire.

2. 2

   Unplug the sensor and inspect the 4-terminal connector for water ingress, corrosion, or bent pins, which can bridge the connections.

3. 3

   With the sensor unplugged and the key in the ON position, use a multimeter to probe the signal wire on the harness side. If it reads a constant 5V or 12V, the short is in the wiring harness. If the voltage is normal (usually 0V on the signal return when unplugged), the sensor itself has an internal short.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the Boost Air Pressure Sensor, which is mounted directly on the intake manifold or the charge air piping coming from the turbocharger.

3. 3

   Disconnect

   Press the release tab and disconnect the 4-pin electrical connector from the sensor.

4. 4

   Remove

   Remove the two mounting bolts securing the sensor to the manifold. Pull the sensor straight out.

5. 5

   Clean

   Inspect the mounting port on the manifold. Wipe away any heavy soot, oil, or debris to ensure the new sensor seats properly.

6. 6

   Install

   Insert the new sensor, ensuring the O-ring is intact and seats flush. Install and tighten the two mounting bolts.

7. 7

   Reconnect

   Plug the electrical connector back in until it clicks securely.

8. 8

   Clear Codes

   Reconnect the battery. Turn the key to the ON position and use a diagnostic scan tool (or the tractor's onboard H-Menu/EIC display) to clear the inactive fault codes.

9. 9

   Test

   Start the engine and verify that the fault code does not return and that the machine is no longer in a derated power state.