Case IH 135 – Engine Controller (ENG / Engine ECU / ECM): Oil Pressure Sensor voltage is too high

The ECM detects a voltage above 4.88 VDC on the oil pressure signal pin. This high voltage condition is typically caused by a signal circuit shorted to the sensor supply or battery voltage, an open return circuit in the engine harness, connectors, or the sensor itself, or a failed oil pressure sensor.

• MX Magnum
• STX Steiger
• Magnum 180 through 340
• STX 280
• STX 440
• Steiger 500
• Steiger 550
• Steiger 580
• Steiger 620
• Maxxum 100
• Maxxum 110
• Maxxum 115
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 135
• Maxxum 140
• Maxxum 145
• Maxxum 150
• Puma 115 through 240
• Optum 250 CVX
• Optum 270 CVX
• Optum 300 CVX
• Farmall 65C
• Farmall 75C
• Farmall 85C
• Farmall 95C
• Farmall 105U
• Farmall JX
• TG Series

1. 1

   Check for other active fault codes, as the oil pressure sensor shares supply and return wires with other sensors, which can cause multiple simultaneous faults

2. 2

   Visually inspect the engine oil pressure sensor connector (Packard-type or DIN-type) and the ECM connector for bent, spread, corroded, or loose terminals

3. 3

   Test the return circuit for an open connection between the sensor harness and the ECM

4. 4

   Test the signal circuit to ensure it is not shorted to the 5V sensor supply or 12V battery voltage

1. 1

   Preparation

   Turn the key switch OFF, set the vehicle parking brake, and chock the wheels.

2. 2

   Disconnect the Sensor

   Locate the engine oil pressure sensor on the engine block (typically to the upper left of the ECM) and disconnect the engine harness from the sensor.

3. 3

   Inspect and Clean

   Check the connector pins for moisture, corrosion, or damage. If the pins are pushed back or damaged, repair the connector.

4. 4

   Test the Harness

   Using a multimeter, verify that the return circuit is intact and that the signal wire is not shorted to a power source. If an open return circuit or shorted signal wire is detected in the engine harness, repair or replace the engine harness.

5. 5

   Replace the Sensor

   If the harness tests good and the connectors are secure, the sensor itself has failed internally. Remove the old sensor and install a new OEM replacement.

6. 6

   Reassembly

   Reconnect the oil pressure sensor to the engine harness.

7. 7

   Clear Codes and Validate

   Turn the key switch ON and connect your electronic diagnostic service tool (e.g., INSITE or equivalent). Clear the inactive fault codes. Start the engine and let it idle for 1 minute. Verify that the amber CHECK ENGINE lamp turns off and that Fault Code 135 remains inactive.