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.
Self-Diagnostic System: Introduction
PCM includes a self-diagnostic system. When a malfunction occurs, PCM will illuminate MIL located on instrument panel. When a problem is detected and light is turned on, a corresponding trouble code will be stored in PCM memory. Problems are recorded as hard failures or as intermittent failures.
There 4 DTC categories:
- Type "A"
Emissions related, turns on MIL the first time DTC sets. - Type "B"
Emissions related, turns on MIL if fault is active for 2 consecutive driving cycles. - Type "C"
Non-emissions related, does not turn on MIL, but will turn on SERVICE light. - Type "D"
Non-emissions related, does not turn on MIL or SERVICE light.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.