DTC P0538: A/C Evaporator Temperature (ACET) Circuit High Input
WARNING: This page does not describe the selected car, but rather 30 other vehicles, including the 2006 Mercury Mountaineer, 2006 Mercury Monterey, 2006 Mercury Montego, 2006 Mercury Mariner, and 2006 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.
P0538 - A/C EVAPORATOR TEMPERATURE (ACET) CIRCUIT HIGH INPUT
| Description: | Indicates the ACET signal input was greater than the self-test maximum. The self-test maximum is 4.5 volts. | ||
| Possible Causes: |
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| Diagnostic Aids: | The powertrain control module (PCM) sources a low current 5 volts on the ACET circuit (this voltage can be measured with the sensor disconnected). As the A/C evaporator air temperature changes, the ACET circuit resistance to SIG RTN (ground) changes (which changes the voltage the PCM detects). When the ACET signal is detected above the self-test maximum, check for open circuits (ACET or SIG RTN), which would cause the voltage to remain high. Although not as probable, also check for a short to voltage (VREF). | ||
| Application | Key On Engine Off | Key On Engine Running | Continuous Memory |
| All | GO to Pinpoint Test DJ . | ||