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.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 4.3 W, STANDARDREPAIR AND DIAGNOSISBRAKESTRACTION CONTROLANTI-LOCK BRAKE SYSTEMDIAGNOSTIC TESTSDTC C0266: PUMP MOTOR RELAY CIRCUIT SHORTEDCIRCUIT DESCRIPTION
1999 GMC Forward Control 4.3 W, Standard
Circuit Description
1999 GMC Forward Control 4.3 W, StandardSECTION Circuit Description
The relay supplies power to pump motor when ABS is required. The relay is located within the EBCM.
Conditions for setting DTC:
- ANTI-LOCK indicator light check complete.
- High voltage on pump motor driver circuit when all are expected to low (relay not commanded on).
RENDER: 1.0x
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.