Customer Background

A Swedish diesel workshop received a vehicle with an intermittent cylinder misfire.

The engine usually operated normally during the first part of the test. After reaching full operating temperature and being stopped briefly, the fault could appear during restart.

Why a Cold Electrical Check Was Incomplete

The workshop initially checked the injector electrical circuit while the engine was cold.

No obvious problem was found.

However, some electrical faults can change as the injector, connector and surrounding wiring become hot.

A measurement taken at workshop temperature therefore did not fully represent the customer complaint.

Testing During the Failure Condition

The technician reproduced the heat-soak condition and monitored injector electrical behavior during the period when the misfire appeared.

Depending on the injector design, suitable electrical measurements may include resistance, insulation condition, supply integrity or waveform analysis.

The workshop also reviewed the connector and wiring harness because an abnormal electrical result does not automatically prove an internal injector failure.

Fault Boundary

The important diagnostic question was whether the fault followed the injector itself or remained within the vehicle electrical circuit.

This distinction allowed the workshop to separate injector replacement from harness or driver-circuit repair.

Case Conclusion

This Sweden case demonstrates why intermittent injector electrical faults should be tested at the temperature and operating state in which the complaint occurs.

A normal cold measurement cannot always rule out a heat-related electrical problem.