1989 Plymouth Horizon AutomaticFACTORY OEM SERVICE PROCEDURE

Check Engine Light

The check engine light will illuminate for 3 seconds as a bulb test every time the ignition is turned on. If the SMEC receives an incorrect or no signal from certain sensors or emission related systems on California vehicles, the check engine light will be illuminated. This warns driver that SMEC has gone into a limp-in mode to keep system operational.

Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.