Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
The following DTCs are for the starter/generator control module (SGCM) coolant fan relay:
- P1AC1 is for the SGCM coolant fan relay control circuit low voltage condition.
- P1AC2 is for the SGCM coolant fan relay control circuit high voltage condition.
The SGCM controls the coolant fan operation by applying voltage to the coolant fan relay control circuit with an internal solid state device called a driver. When the SGCM is commanding the relay ON, the voltage of the control circuit should be low, near 0 volts. When the SGCM is commanding the relay OFF, the voltage potential of the control circuit should be high, near 12 volts.
The SGCM monitors the relay control circuits for the following conditions:
- Short to ground
- Short to voltage
- An open circuit
If the SGCM detects an improper voltage level on the coolant fan relay control circuit, then DTC P1AC1 or P1AC2 will set and the driver will be disabled.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.