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 MANUALSGMC1991JIMMY 5.7 K, AUTOMATIC, 4L60/MD8REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETHEORY AND OPERATIONENGINE CONTROLS - THEORY & OPERATIONCOMPUTERIZED ENGINE CONTROLS (GASOLINE)OUTPUT SIGNALS
1991 GMC Jimmy 5.7 K, Automatic, 4L60/MD8
Output Signals
1991 GMC Jimmy 5.7 K, Automatic, 4L60/MD8SECTION Output Signals
NOTE:
Vehicles are equipped with different combinations of computer-controlled components. Not all components listed below are used on every vehicle. For theory and operation of components, refer to indicated system.
- A/C CLUTCH RELAY refer to MISCELLANEOUS ECM CONTROLS .
- AIR INJECTION CONTROL SOLENOID see EMISSION SYSTEMS (GAS) .
- CHARGE AIR COOLER PUMP RELAY (4.3L TURBO) refer to TURBOCHARGER .
- COOLING FAN RELAY (3.1L) refer to MISCELLANEOUS ECM CONTROLS .
- SERVICE ENGINE SOON LIGHT refer to SELF-DIAGNOSTIC SYSTEM .
- EGR CONTROL SOLENOID VALVE refer to EMISSION SYSTEMS (GAS) .
- ESC TIMING RETARD refer to IGNITION SYSTEM .
- EVRV SOLENOID refer to EMISSION SYSTEMS (GAS) .
- FUEL INJECTORS refer to FUEL CONTROL (GAS) .
- FUEL MODULE refer to FUEL DELIVERY (GAS) .
- FUEL PUMP & FUEL PUMP RELAY refer to FUEL DELIVERY (GAS) .
- HEI-EST IGNITION refer to IGNITION SYSTEM .
- IDLE AIR CONTROL (IAC) VALVE refer to IDLE SPEED (GAS) .
- SELF-DIAGNOSTICS refer to SELF-DIAGNOSTIC SYSTEM .
- SERIAL DATA refer to SELF-DIAGNOSTIC SYSTEM .
- SHIFT SOLENOIDS (4L80-E TRANSMISSION) refer to MISCELLANEOUS ECM CONTROLS .
- TORQUE CONVERTER CLUTCH refer to MISCELLANEOUS ECM CONTROLS .
- TRANSMISSION SHIFT LIGHT (MANUAL TRANSMISSION) refer to MISCELLANEOUS ECM CONTROLS .
- TURBO BOOST RELAY (4.3L TURBO) refer to TURBOCHARGER .
- WASTEGATE SOLENOID (4.3L TURBO) refer to TURBOCHARGER .
RENDER: 1.0x
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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.