John Deere 637.05 – ECU: Issue With Signal From Crankshaft Position Sensor High Resistance (ECU)

The Engine Control Unit (ECU) has detected abnormally low current on the crankshaft position sensor wiring. The circuit resistance is too high, which typically indicates an open circuit, a broken wire, or an intermittent harness/connector problem. Because this sensor monitors rotational speed and crankshaft position to control fuel injection timing, a failure here can cause engine performance issues or prevent the engine from running.

• 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
• 9230
• 9330
• 9430
• 9530
• 9630
• 8230
• 8235R
• 8245R
• 8260R
• 4930 Self-Propelled Sprayer
• 9660STS
• 9760
• 3520
• 3522
• 120
• 130G
• 160C
• 210G
• 310G
• 310J
• 310K
• 450J
• 605C

1. 1

   Visually inspect the wiring harness leading to the crankshaft position sensor for chafing, breaks, or pinched wires.

2. 2

   Disconnect the sensor and check the connector pins for corrosion, moisture, or loose terminals that could cause an intermittent connection.

3. 3

   Use a multimeter to check the continuity of the sensor wiring back to the ECU to confirm if the open circuit is in the harness or internal to the sensor itself.

1. 1

   Disconnect battery

   Turn the machine off and disconnect the battery to ensure safety while working on the engine electrical system.

2. 2

   Locate sensor

   Locate the Crankshaft Position Sensor (typically located on the right side of the front engine cover near the crankshaft pulley/spur gear).

3. 3

   Repair wiring harness

   If the diagnostic checks revealed a broken wire or damaged connector, repair or replace the affected harness section. Clear the codes and test the machine.

4. 4

   Disconnect sensor wiring

   If the wiring and connector are in good condition, the sensor itself has failed internally (open circuit). Disconnect the wiring harness from the sensor.

5. 5

   Remove old sensor

   Remove the mounting bolt holding the sensor in place and pull the old sensor out of the engine block/cover.

6. 6

   Install new sensor

   Install the new OEM Crankshaft Position Sensor. (Note: These are inductive sensors with a fixed distance to the spur gear, so ensure the mounting surface is clean so it seats properly).

7. 7

   Reconnect and clear codes

   Reconnect the wiring harness, reconnect the battery, and clear the ECU fault codes.

8. 8

   Test engine

   Start the engine and verify that the code does not return and that engine RPM is reading correctly.