New Holland ENG 338 – ENGINE (ECM / ENG): Idle Shutdown Vehicle Accessory Relay Voltage is too high.

This indicates a circuit fault where the engine control module detects that the voltage on the circuit responsible for the Idle Shutdown Vehicle Accessory Relay is exceeding the expected or maximum allowable threshold. This typically points to a short to power in the wiring harness, a failed relay, or an internal fault within the controller.

• Tractors and equipment utilizing 8.3 Liter, 9.0 Liter, and 15 Liter engines
• New Holland T7.270

1. 1

   Locate the Idle Shutdown Vehicle Accessory Relay in the machine's main fuse/relay distribution box.

2. 2

   Inspect the wiring harness between the Engine ECM and the accessory relay for any chafing or melting that could cause a short to a 12V/24V power source.

3. 3

   Remove the relay and test it for internal shorts. A fused or internally shorted relay coil can send high voltage back to the ECM driver.

4. 4

   Inspect the Engine ECM connectors for corrosion, water ingress, or bent pins that might be bridging power to the accessory relay control circuit.

1. 1

   Disconnect battery

   Disconnect the battery to prevent electrical spikes.

2. 2

   Remove relay

   Remove the suspected Idle Shutdown Vehicle Accessory Relay.

3. 3

   Verify short to power

   Using a multimeter, verify if the short to power exists on the control wire leading back to the Engine ECM.

4. 4

   Repair wiring

   If the wire is shorted, trace the harness and repair or replace the damaged section of the wiring loom.

5. 5

   Replace relay

   If the wiring tests good, replace the faulty accessory relay.

6. 6

   Reconnect and test

   Reconnect the battery, clear the inactive fault codes via the diagnostic menu or service tool, and run the engine to verify the code does not return.