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, AutomaticFACTORY OEM SERVICE PROCEDURE
Test QD - Introduction
NOTE:
Perform this test when Codes 71, 72 or 78 is displayed or when directed by other test procedure or driveability symptoms. This test is intended to diagnose only the following:
- ECA
- EEC Power Relay
- Harness circuits (GND, VPWR, IGNITION)
NOTE:
The electrical signatures of some aftermarket components may affect driveability of the vehicle.
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.