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.
Powertrain Diagnostic System Check
Powertrain diagnostic system check determines:
- If Malfunction Indicator Light (MIL) operates.
- If ECM is operating and can recognize a fault.
- If any DTCs are stored.
After performing procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the OBD system check, if no DTCs are indicated and driveability problems still exist, see appropriate TROUBLE SHOOTING - NO CODES article and SCAN TOOL USAGE .
- Connect scan tool to 16-pin DLC located under left side of instrument panel. See Fig 1 . If scan tool does not power up, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article. If scan tool powers up, go to next step.
- Attempt to establish communications, read and record DTCs from BCM, SDM, ECM and ABS (if equipped) modules. If scan tool communicates with BCM, go to step 4 . If scan tool does not communicate with BCM, go to next step.
- If scan tool communicates with SDM, go to step 5 . If scan tool does not communicate with SDM, see NO COMMUNICATION ON CLASS-2 DATA LINK in appropriate BODY CONTROL MODULES article.
- If any DTCs are set in BCM, see appropriate test under DIAGNOSTIC TESTS in appropriate BODY CONTROL MODULES article. If no DTCs are set in BCM, go to next step.
- If any DTCs are set in SDM, see appropriate test under DIAGNOSTIC TESTS in appropriate BODY CONTROL MODULES article. If no DTCs are set in SDM, go to next step.
- If DTCs are set in ECM, see DIAGNOSTIC TROUBLE CODE INDEX under DIAGNOSTIC TROUBLE CODE DEFINITION. If no DTCs are set in ECM, go to next step.
- If scan tool communicates with EBTCM, go to next step. If scan tool does not communicate with EBTCM, see NO COMMUNICATION WITH EBTCM in appropriate BODY CONTROL MODULES article.
- If DTCs are present in EBTCM, see DIAGNOSTIC TESTS in appropriate ANTI-LOCK/TCS article. If no DTCs are present in EBTCM, go to next step.
- If engine starts and runs, diagnostic system check is complete. If problem exists, observe scan tool data and/or refer to symptom in appropriate TROUBLE SHOOTING - NO CODES article. If engine does not start and run, see appropriate BASIC DIAGNOSTIC PROCEDURES article.
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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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