Diagnostic Trouble Code (DTC): P0494
P0494 code definition
If the PCM has detected a voltage reading that is too low from the electric cooling fan control circuit, the P0494 code will be stored.
What the P0494 code means
The P0494 code relates to the engine cooling and air conditioner systems. In order ensure that the engine temperature remains at the right level, and that the air conditioner is operating correctly, the PCM gathers data from the circuitry in the cooling fan control system. If this data is more than 10% lower than the voltage specified by the manufacturer for the current driving conditions, then the PCM will store the P0494 code.
What causes the P0494 code?
- Loose or corroded electrical connectors
- A faulty engine coolant temperature sensor
- Open or shorted electrical wiring (which may or may not be accompanied by blown fuses)
- A faulty cooling fan clutch
- A faulty cooling fan control unit
What are the symptoms of the P0494 code?
In most cases, the illuminated Check Engine Light will be the only observable symptom. Some vehicles may overheat, and the air conditioner may not work as efficiently.
How does a mechanic diagnose the P0494 code?
After verifying the code with an OBD-II scanner, the mechanic should begin with a visual inspection of all wiring and other electrical components, as well as vacuum lines and hoses. Any simple electrical issues, such as loose or shorted elements, should be repaired.
After this, or any, repair, it is important to clear the code and retest the system. If the code returns, then the mechanic must continue by checking the voltage of the primary cooling fan motor. The next step is to check the voltage readings of the engine cooling fan relay. If either of these parts are not meeting the manufacturer’s specifications, they must be replaced.
The mechanic should continue in this manner, diagnosing and retesting the system after each possible diagnosis, until the cause is found.
Common mistakes when diagnosing the P0494 code
The most common mistake when diagnosing and repairing this code is to replace a cooling fan motor without performing a thorough diagnostic procedure of the entire system. For example, cooling fan relays are frequently recalled, and may therefore be the true issue. It is important to diagnose all possible problems before replacing any major parts.
How serious is the P0494 code?
If the P0494 code is stored in the PCM, it represents a serious issue that should be repaired immediately. Although no major symptoms are usually observed, the inability to measure and control the cooling system will eventually lead to larger and more expensive repairs. It is important to have this issue fixed as soon as the code is detected.
What repairs can fix the P0494 code?
There are a few ways that a technician can address a P0494 code detection. They include:
- Replace a bad cooling fan motor
- Replace a bad cooling fan relay
- Repair any loose or corroded electrical connectors
- Replace a faulty engine coolant temperature sensor
- Repair any open or shorted electrical wiring
- Replace a faulty cooling fan clutch
- Replace a faulty cooling fan control unit
Need help with a P0494 code?
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