John Deere 636.08 – ECU: Camshaft Position Sensor Signal Missing or Pump Position Sensor Input Missing

The control module is not receiving an input signal from the camshaft/pump position sensor. Because this signal is missing, the controller cannot accurately detect camshaft speed or engine position. This failure significantly impacts engine management and timing, resulting in excessive/prolonged cranking times, engine misfires, intermittent stalling, reduced engine performance, or a complete no-start condition.

• 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
• 7930
• 9200
• 9300
• 9400
• 9420
• 750J
• 850J
• 319D
• 328D
• 744H
• 4045TFM
• 6068TFM

1. 1

   Inspect the camshaft position sensor wiring harness for chafing, melting, or physical damage.

2. 2

   Disconnect the sensor and check the pins for corrosion, moisture, or pushed-out terminals. Ensure the connector is firmly seated.

3. 3

   Perform a load test on the cam sensor wires to check for an open circuit or high resistance between the sensor connector and the ECU.

4. 4

   Use a diagnostic tool (like John Deere Service ADVISOR) to monitor engine RPM during cranking. Check if the ECU is registering a signal from the crankshaft sensor but nothing from the camshaft sensor.

1. 1

   Prep the Machine

   Park the machine on a level surface, turn off the engine, remove the key, and disconnect the negative battery cable.

2. 2

   Locate the Sensor

   Locate the camshaft position sensor (sometimes referred to as the pump position sensor on specific injection pumps). It is typically mounted on the timing gear cover or near the injection pump drive.

3. 3

   Remove the Sensor

   Depress the locking tab and unplug the electrical connector. Remove the retaining bolt(s) holding the sensor in place.

4. 4

   Extract and Inspect

   Carefully pull the sensor straight out of its bore. Inspect the tip of the old sensor for physical damage (which could indicate internal gear issues).

5. 5

   Install the New Sensor

   Lubricate the O-ring on the new sensor with clean engine oil. Insert the sensor into the bore until it seats fully.

6. 6

   Secure and Reconnect

   Install and tighten the retaining bolt to OEM torque specs. Reconnect the wiring harness until it clicks into place.

7. 7

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic scanner to clear the 000636.08 / SPN 636 FMI 8 fault code. Start the engine to verify the repair.