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
Ignition voltage is supplied directly to cooling fan relay coil. PCM controls relay by grounding control circuit through an internal switch called a driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by PCM.
When PCM is commanding a component ON, voltage of control circuit should be low (near zero volts). When PCM is commanding control circuit to a component OFF, voltage potential of circuit should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, fault line status will change, causing DTC to set.
DTC will set when the following conditions are present:
- Engine speed greater than 600 RPM.
- Ignition voltage between 6-16 volts.
- PCM detects commanded state of driver and actual state do not match.
- Conditions met for 10 seconds.
NO RELATED
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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.