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.
1990 Jeep Wrangler SFACTORY OEM SERVICE PROCEDURE
Functional Test
- Shut off engine and note if ISA motor plunger extends. If necessary to extend plunger for test, an ISA motor failure can be suspected. Adjust ISA motor if necessary. With ignition switch in ON position, test switch voltage at diagnostic connectors D2-13 and D2-7 (ground). See Fig 1 .
- Voltage should be close to zero at closed throttle and greater than 2 volts when throttle is not closed. If no voltage is present in either position, test for short circuit to ground in wire harness or switch. Test for open circuit between ECU connector terminal No. 25 and switch.
- If voltage is always more than 2 volts, test for open circuit in wire harness between ECU and switch connector, and between switch connector and ground. Repair or replace wire harness as necessary.
Factory Service Tools
Use the Manual With the Right Hardware
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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.