JCB P0205 – ECM: Injector Cylinder 5 Open Circuit

The Engine Control Unit (ECU) has detected an open circuit in the control circuit for the 5th cylinder's fuel injector. This indicates a break in the electrical path, which prevents the injector from receiving the proper electrical signal to function correctly. Because the ECU cannot successfully command the injector to open, this condition typically results in a cylinder 5 misfire (which may log a separate P0305 code), leading to rough or unstable idle, noticeable loss of power and acceleration, vibration or stumble, increased fuel consumption, potential for the engine to stall, and illumination of the Malfunction Indicator Lamp (MIL) or 'Check Engine' light.

• Dieselmax 672
• JS130
• JS145W
• JS200
• JS200W
• JS205
• JS210
• JS220
• JS235
• JS240
• JS260
• JS290
• JS330
• JS360
• JS370
• Tracked Excavators
• Wheeled Excavators

1. 1

   Visually inspect the wiring harness and electrical connector for the cylinder 5 fuel injector for chafing, burnt or melted insulation, corrosion (green powder), or loose pins. Perform a wiggle test with the engine running to check for intermittent connections.

2. 2

   Check for battery voltage at the injector's electrical connector with the ignition on using a multimeter or 12V test light.

3. 3

   Perform a noid light test by plugging a noid light into the disconnected injector connector and cranking the engine to verify the ECM is sending a pulse signal.

4. 4

   Measure the resistance across the two terminals of the disconnected cylinder 5 injector and compare it to the other injectors (common rail diesel injectors are typically 0.4-0.8 ohms, other diesel injectors 2.8-3.6 ohms, and automotive-style 10-18 ohms). An infinite reading indicates an open circuit inside the injector.

5. 5

   Perform a continuity test on the wiring harness between the ECM connector and the injector connector (resistance should be less than 0.5 ohms).

1. 1

   Confirm fault and gather data

   Use a diagnostic scanner to confirm P0205 is active and check for related codes like P0305 (Cylinder 5 Misfire). Record freeze-frame data.

2. 2

   Isolate the faulty component

   Determine the failure point based on diagnostic checks. Damaged wiring/connectors are the most likely cause. An open resistance reading points to a failed injector. If the noid light failed but wiring continuity is good, the ECM injector driver may be at fault (rare).

3. 3

   Swap injectors for confirmation

   If the injector is suspected, swap the cylinder 5 injector with another cylinder (e.g., cylinder 4). Clear codes and run the engine. If the fault changes to P0204, the injector is definitively faulty.

4. 4

   Repair wiring or replace injector

   Repair broken wires or replace damaged connector pigtails. If replacing the injector, ensure the new injector is installed correctly with new sealing washers and O-rings. The ECM may need to be coded or calibrated to the new injector.

5. 5

   Clear codes and verify repair

   Clear the fault codes from the ECM using a scanner. Start the engine and verify it runs smoothly without the code returning.