JCB P0335 – ECM: Crankshaft Position Sensor 'A' Circuit Fault

The Engine Control Module (ECM) has detected a fault in the electrical circuit of the crankshaft position sensor 'A'. This indicates an issue with the electrical connection or functionality of the sensor that monitors the position and rotational speed of the crankshaft. The ECM relies on this signal for controlling ignition timing and fuel injection. A lost or irregular signal can lead to a failure to start, intermittent stalling, and reduced power. On JCB Ecomax engines, this fault may result in a 60% reduction in available engine torque or a complete engine stop in cases of a crank signal overspeed fault.

• 3CX Backhoe Loader
• 4CX Backhoe Loader
• JS130 Excavator
• JS160 Excavator
• JS200 Excavator
• 210 Loader
• 220 Loader
• 230 Loader
• Telescopic Handlers
• Dieselmax engines (444 and 448 models)
• Ecomax engines

1. 1

   Ensure the engine is off and has cooled down, and disconnect the battery to prevent accidental starting

2. 2

   Visually inspect the crankshaft position sensor's wiring harness for fraying, breaks, or heat damage

3. 3

   Examine the electrical connector for corrosion, loose pins, or a poor connection, ensuring it is securely fastened

4. 4

   Use a diagnostic scan tool to monitor the live engine RPM signal while cranking; a reading of zero or an erratic signal indicates a circuit problem

5. 5

   Check for related fault codes, particularly those associated with the camshaft position sensor

6. 6

   With the sensor disconnected and ignition on, use a multimeter to verify a 5V reference voltage from the ECM and a good ground connection at the connector

1. 1

   Make machine safe

   Ensure the machine is on level ground, parking brake applied, engine off and cool. Disconnect the battery.

2. 2

   Gain access to sensor

   Locate the sensor on the engine block or flywheel housing. Remove any under-covers or protection plates as needed.

3. 3

   Remove faulty sensor

   Disconnect the electrical connector by depressing the locking tab. Remove the mounting bolt(s) and gently twist and pull the sensor straight out of its housing.

4. 4

   Install new sensor

   Apply a light coat of clean engine oil or grease to the new sensor's O-ring. Insert fully into the mounting hole and tighten mounting bolts to the manufacturer's specified torque (do not over-tighten).

5. 5

   Reconnect and test

   Reconnect the electrical connector until it clicks. Reinstall covers, reconnect the battery, clear the P0335 code with a scan tool, and test drive to confirm the repair.