Case IH P35 – Engine Control Unit (ECU / ECM): Boost Air Pressure Sensor (PHY), Data Valid But Above Normal Range

Code T35 indicates that the Engine Control Module (ECM) is receiving a signal from the Boost Air Pressure (MAP) sensor that is electrically valid, but the pressure reading is higher than the normal expected operating range for the current engine speed and load. This means the engine is either experiencing a genuine mechanical overboost condition, or the sensor's internal calibration has skewed, causing it to report a falsely high pressure.

• MXM
• MXM Series
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• Maxxum
• Puma
• Magnum
• MX275
• Axial-Flow
• 7010
• 7230
• 8230
• 9230
• TM Series
• TM115-TM165
• T6 series

1. 1

   Verify Actual Boost: Connect a mechanical boost pressure gauge to the intake manifold. Run the engine under load to see if the turbocharger is actually overboosting. If mechanical boost is normal, the sensor is lying.

2. 2

   Inspect the Wastegate: If the engine is genuinely overboosting, check the turbocharger wastegate actuator and linkage for mechanical binding or a ruptured actuator line.

3. 3

   Wiring & Connector Check: Inspect the sensor's electrical connector (often located on the intake manifold or just above the engine oil filter). Look for corrosion, moisture, or chafing in the harness that could add resistance and skew the 5V reference signal.

4. 4

   Check for Related Codes: Look for codes T36 (Data Incorrect) or T37 (Shorted to High Source), which would further confirm a failing sensor circuit.

5. 5

   If diagnosing code P35 (PTO switch): Inspect the fender-mounted PTO switch wiring for a short to 12V or a crushed harness against the fender sheet metal.

1. 1

   Cool engine

   Turn off the machine, remove the key, and allow the engine to cool.

2. 2

   Locate sensor

   Locate the boost pressure sensor. On many Case IH engines (like the 8.3L/9.0L), it is mounted directly on the intake manifold or on the block just above the oil filter.

3. 3

   Disconnect harness

   Depress the locking tab and disconnect the electrical wiring harness from the sensor.

4. 4

   Remove retaining bolt

   Remove the retaining bolt(s) securing the sensor to the manifold.

5. 5

   Remove sensor

   Carefully pull the old sensor straight out.

6. 6

   Clean mounting port

   Clean the mounting port on the manifold to ensure no debris falls into the intake.

7. 7

   Lubricate O-ring

   Lubricate the O-ring on the new sensor (e.g., 11.3mm ID x 2.2mm thick O-ring) with a small amount of clean engine oil.

8. 8

   Install new sensor

   Push the new sensor into place and tighten the retaining bolt to OEM torque specs.

9. 9

   Reconnect harness

   Reconnect the electrical harness, ensuring it clicks into place.

10. 10

    Clear codes and test

    Turn the key on and clear the inactive fault codes via the H-Menu or diagnostic tool, then test run the machine under load.