A heater-related fault detected from cold needs the first-start conditions preserved. A warm engine check may not exercise the same monitoring or electrical demand.
Arrange the relevant assessment
Tell the workshop how long the vehicle must rest for the warning to return. Provide exact sensor location, code and any recent exhaust work. A sensor’s signal behaviour when warm does not independently verify its heater circuit.
Do not apply battery voltage to unknown terminals or use an assumed universal resistance. The correct test depends on the sensor and circuit. Ask which supply, control and load checks were completed cold, and preserve the original report before a reset or warm journey removes the best opportunity to observe the fault.
Need help with this fault?
Browse this collection or prepare a vehicle and module enquiry. Tell us about the vehicle, the fault and any tests already done. Contact our Didcot workshop before travelling or posting a module. Visits are by appointment.