Generic fault code
P0542 — Intake air heater A, circuit: signal high
The control unit stores code P0542 when it detects this fault: “Intake air heater A, circuit: signal high”.
Indicative severity: MediumFuel and air metering
Reviewed by Daniel Morales, founder of Reprorace SL, on
What does code P0542 mean?
The engine measures the incoming air and meters the fuel so the mixture is right; the throttle, the accelerator pedal and the turbo are here too. A fault usually shows as higher fuel use, jerking, lack of power or hard starting.
- System
- P · Powertrain
- Area
- Fuel and air metering · Car system: Fuel and air
- Type
- Generic (SAE J2012 / ISO 15031-6): the same meaning on every make
- Indicative severity
- Medium. Diagnose soon: it may raise emissions or consumption, or trigger limp-home mode.
What usually causes code P0542?
- Short circuit to battery or another voltage
- Open circuit (broken wire or terminal)
- Loose or corroded connector, backed-out terminals
The most likely causes come first. Only a check on the car confirms which one is yours.
What are the symptoms of code P0542?
- Jerking or lack of power
- Rough idle or stalling
- Higher fuel use and, on diesels, black smoke
These are the usual symptoms of this kind of fault: not all of them always appear, and sometimes you notice nothing.
Can I keep driving with code P0542?
With care, and not for long. You can take the car to a workshop, ideally without long trips or heavy loads, and without putting it off: fuel use or emissions may rise and the car may go into limp-home mode (less power). If the light flashes, a red warning light comes on, the temperature rises or you notice a loss of power, noises or smoke, stop as soon as it is safe.
This is guidance only: only someone who checks the car can say whether it is safe to drive.
An indicative description of the code's generic meaning. Each manufacturer may give it a different meaning, conditions or tests: always follow its service information and your workshop's advice.
What you can do yourself
For this kind of fault
Check that the air filter is clean and that the duct between the filter and the engine has no cracks or loose clamps. Do not clean the air flow sensor with products not made for it.
Read the code and keep the report: with an ECO-LITE in the OBD socket you see it on your phone or computer, with the data captured when the fault happened.
Look for anything obvious: a loose connector, a disconnected hose, a fuel cap not closed properly or a low fluid level. Do not take apart anything you do not know.
Clear the code only after writing it down or after the repair. Clearing turns the light off, but it also deletes the freeze-frame data and the readiness monitors used at the inspection.
Drive normally for a few days and read the codes again. If the code comes back, the fault is still there: book the workshop and bring the report.
Read your car's fault codes on your phone
With an ECO-LITE in the OBD socket you see the codes in your account, with the data captured when the fault happened, and your workshop can check them remotely, always with your permission.
Related codes
- P0540Intake air heater A, circuit: malfunction
- P0541Intake air heater A, circuit: signal low
- P0543Intake air heater A, circuit open
- P0640Intake air heater, control circuit: malfunction
- P065EIntake manifold tuning valve (bank 1): performance
- P065FIntake manifold tuning valve (bank 2): performance
P05xx codes: vehicle speed, idle control and auxiliary inputs
In the glossary
Read more: Remote OBD diagnostics: what it is, how it works and what it can't do