Case IH 3089 – Engine Control Unit (ECU) / ECU A-095: Crankshaft speed sensor pattern is not plausible

The engine control module evaluates the signals received from both the camshaft and crankshaft speed sensors to determine engine angle, speed, signal plausibility, and quality. If the module determines that more than eighty crankshaft signal plausibility errors have occurred, this fault code is triggered. This indicates the controller is receiving erratic, missing, or out-of-sync data from the crankshaft sensor, preventing it from accurately timing the fuel injection process.

• Farmall
• skid steer
• Steiger T4B
• Magnum (235–340 Series 4)
• Puma (130–225)
• Maxxum (100–150)
• Steiger (350–600)
• Farmall (85C)
• 240 Series Axial-Flow Combines

1. 1

   Verify that the tractor battery has not been connected to an external power supply (e.g., a jump box or charger). Disconnect if present and retest.

2. 2

   Check the battery voltage on the instrument cluster with the engine running at 2000 RPM to ensure the alternator is charging correctly.

3. 3

   Inspect the system for a faulty charging system, a faulty solenoid, or a faulty Central Control Unit (CCU).

4. 4

   Inspect the wire harness leading to the crankshaft speed sensor for shorts, open circuits, or chafing.

5. 5

   Check the gap between the sensor tip and the flywheel teeth (typically 0.5mm to 2.0mm) and ensure the mounting surface is clean.

1. 1

   Locate sensor

   Locate the crankshaft speed sensor, which typically mounts on the side of the engine block near the flywheel housing.

2. 2

   Disconnect sensor

   Disconnect the electrical connector from the sensor.

3. 3

   Remove sensor

   Remove the retaining bolt(s) holding the sensor in place and pull the sensor straight out of the block.

4. 4

   Clean mounting surface

   Clean the mounting surface thoroughly to ensure the new sensor sits flush. Debris can alter the sensor gap and cause immediate implausibility codes.

5. 5

   Install new sensor

   Install the new crankshaft speed sensor. (Note: The magnetic pickup design is weather-sealed and requires no modifications).

6. 6

   Reconnect harness

   Reconnect the wiring harness.

7. 7

   Clear codes and test

   Clear the fault codes from the ECU and test-run the machine to verify the repair.