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 Ford Bronco II RWD, Standard, M5OD-R1FACTORY OEM SERVICE PROCEDURE
Idle Speed Control (ISC) By-Pass Solenoid
- Ensure ignition is off. Disconnect ISC solenoid connector. Set DVOM to 200-ohm scale. Measure resistance across ISC solenoid terminals. If resistance is 7-13 ohms in one direction and higher in the opposite direction (because of diode), solenoid is okay.
- Set DVOM to 20 k/ohm scale. Measure resistance from either ISC solenoid terminal to ISC solenoid housing. If resistance is greater than 10 k/ohms, ISC solenoid is okay.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.