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 MANUALSCADILLAC1991FLEETWOOD FWD V8-300 4.9LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSRELAYS AND MODULES - COMPUTERS AND CONTROL SYSTEMSIDLE/THROTTLE SPEED CONTROL UNITTESTING AND INSPECTION
1991 Cadillac Fleetwood FWD V8-300 4.9L
Idle/Throttle Speed Control Unit: Testing and Inspection
1991 Cadillac Fleetwood FWD V8-300 4.9LSECTION Testing and Inspection
Switch Test E.7.2:
ISC Circuit:
DISPLAY CONFIGURATION:
After .7.0 is displayed on the Fuel Data Center (FDC), the PCM/ECM switch test can be initiated by depressing the brake pedal when the brake pedal has been depressed the FDC will display E.7.0. AT this time the HI and LO buttons on the Electronic Climate Control (ECC) panel can be used to select the specific switch test. When a specific test has been selected and that switch activated, the display will alternately display the code for that test and E.0.0 to confirm the switch is working.
TEST DESCRIPTION:
This test detects the open and close of the nose switch of the Idle Speed Control (ISC) at terminal A7 of the PCM/ECM.
NOTES ON FAULT TREE:
1. The throttle body must be removed to disconnect the ISC jumper from the ISC. An ohmmeter should be used to inspect the jumper for opens and shorts. The ISC throttle switch can also be checked with an ohmmeter for switch operation.
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.