John Deere 637.08 – ECU: Crank Sensor Signal Input Missing

The controller does not detect the input signal from the crankshaft speed/position sensor, which can result in improper engine timing, reduced performance, and the system entering limp mode or derating engine power.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5065M
• 5075M
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5095M
• 5095MH
• 5105M
• 5015ML
• 5090M
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6010-6510 series
• 7185J-7225J series
• 8230
• 9230-9630 series
• 9560 STS
• 9660 STS
• 9760 STS
• 9860 STS
• 444J
• 544J
• 624J
• 750J
• 850J
• 120
• 130G
• 310G
• 450J

1. 1

   Inspect the wiring harness leading to the crankshaft position sensor for an open circuit, a short circuit, or damaged wiring.

2. 2

   Check the sensor connections to ensure they are secure, free of corrosion, and not causing an intermittent signal loss.

3. 3

   Verify that the sensor is installed correctly and check the 'target sensitivity' (the gap/alignment between the sensor and the crankshaft tone ring).

1. 1

   Power down machine

   Power down the machine and engage the parking brake.

2. 2

   Locate sensor

   Locate the Crankshaft Position Sensor on the engine block.

3. 3

   Inspect and repair harness

   Disconnect the electrical harness from the sensor and inspect the pins for damage or moisture. Repair the harness if an open circuit or wiring fault is found.

4. 4

   Remove old sensor

   If the wiring and connections are intact, the sensor itself has likely failed internally. Remove the mounting bolt and extract the old sensor.

5. 5

   Install new sensor

   Install the new OEM crankshaft position sensor, ensuring it is seated correctly to maintain the proper reading gap.

6. 6

   Reconnect harness

   Reconnect the wiring harness.

7. 7

   Clear codes and verify

   Clear the ECU fault codes using a diagnostic tool or monitor, then start the engine to verify that proper engine timing and performance are restored and the code does not return.