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P0543 OBD-II Trouble Code: Intake Air Heater "A" Circuit Open

check engine light

P0543 code definition

Detecting the P0543 code indicates that the PCM is reading an abnormal amount of input voltage from the intake air heater circuit.

What the P0543 code means

The engine control module, or ECM, uses an intake air heater that warms incoming air in order to achieve proper cylinder combustion. The ECM detects the voltage on the intake air heater circuits in order to determine that the heater is performing correctly. If the voltage is too high, the ECM assumes that the heater is in the open position when it isn’t meant to be, and will alert the PCM to store the P0543 code.

What causes the P0543 code?

The most common underlying issue for the P0543 code is a faulty intake air heater relay.

Other causes may include:

What are the symptoms of the P0543 code?

In most cases, the only symptoms will be the P0543 code stored in the PCM, and the illumination of the Check Engine lamp.

How does a mechanic diagnose the P0543 code?

After an OBD-II scanner detects the P0543 code, the first diagnostic step taken should be a visual inspection of all the wiring, connectors, and other electrical components. Any damaged elements should be replaced, reconnected, or repaired as necessary. Once this procedure is complete, the mechanic should then clear the code and test the system. If the code returns, they have successfully diagnosed an issue with the intake air heater and/or its circuit.

Common mistakes when diagnosing the P0543 code

In many cases, technicians or vehicle owners replace dirty air filters, or remove the air cleaner box for repairs, during a tune up, and do not reconnect the intake air temperature sensor correctly. It is common for some mechanics to begin replacing the intake air heater relay or other parts, before checking if a bad connection is the underlying issue.

How serious is the P0543 code?

If the P0543 code is being detected, the issue needs to be addressed right away. The vehicle’s ability to create the proper environment for cylinder combustion is vital to the overall operation, making this a very serious malfunction. Even though no symptoms may be present, it is important to have this repair performed right away when detected.

What repairs can fix the P0543 code?

There are many ways that a technician can address a P0543 code detection. They include:

It is important that after each repair, the mechanic clear the code from the PCM and preform a system test. If the code returns during the test, the previous repairs did not address the issue, and the mechanic must continue with diagnostics and repair. This process helps mechanics to pinpoint exactly what caused the issue in the first place, which can make future repairs much easier should the issue arise again.

Need help with a P0543 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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