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.

2002 Saturn SC2 Automatic, MP6FACTORY OEM SERVICE PROCEDURE

HVAC, Manual DTCS

HVAC, MANUAL DIAGNOSTIC TROUBLE CODE (DTC) LIST

DTC	Description
B3785	Highblow Relay Output Short To Battery Or Open
B3787	Highblow Relay Output Short To Ground
P0646	A/C Clutch Relay Circuit Low Voltage
P0647	A/C Clutch Relay Circuit High Voltage

Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

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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.