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 Laredo, AutomaticFACTORY OEM SERVICE PROCEDURE
Power Circuits
- Using a voltmeter, turn ignition on and check for voltage between MCU terminals No. 1 and 57. If battery voltage is not present, check IGN/LPS fuse. If fuse is okay, check for an open wires between fuse box and control unit.
- Connect a voltmeter between ground and MCU terminal No. 58. Turn ignition switch to the START position. Battery voltage should be present between control unit terminal No. 58 and ground. If voltage is not present, check for an open in Green wire between MCU and ignition switch, or check for a defective ignition switch.
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.
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