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 Plymouth Laser Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Harness Check
- If during SELF-DIAGNOSTICS testing Electronic Control Unit (ECU) is found to be faulty, perform the following steps to ensure ECU is faulty.
- Most components are incorrectly diagnosed due to faulty electrical connectors or poor connections between component and vehicle.
- Sometimes, simply disconnecting and connecting an electrical component will provide a good electrical connection. Before replacing an ECU, check all components in suspect circuit. If components are okay, carefully disconnect ECU from vehicle harness.
- Inspect ECU harness connector and ECU contact pins for corrosion. Clean harness connector and ECU contact pins with contact cleaner.
- Inspect ECU harness connector for bent pins, missing pins and broken wires. Replace as necessary.
- Connect ECU harness connector to ECU and retest system with Diagnostic Readout Box (DRB-II) or similar scan tool. See appropriate SELF-DIAGNOSTICS article. If vehicle does not pass test and fails with the same message, replace ECU.
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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