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.
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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 545 (CHARGING SYSTEM)DIAGNOSTIC TESTSDTC P0622: IMPROPER PULSE WIDTH MODULATED SIGNAL (DIESEL ENGINE)DIAGNOSTIC PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Diagnostic Procedure
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- If diagnostic system check was not performed, perform ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM. If diagnostic system check was performed, go to next step.
- Test Gray wire for a short or an open between generator harness connector terminal "C" and ECM harness connector C2 terminal No. 52. See WIRING DIAGRAMS . If problem exists, repair as necessary. After repair, go to step 6 . If problem does not exist, go to next step.
- Inspect generator harness connector for poor connections. If problem exists, repair as necessary. After repair, go to step 6 . If problem does not exist, go to next step.
- Inspect ECM harness connector for poor connections. If problem exists, repair as necessary. After repair, go to step 6 . If problem does not exist, go to next step.
- Replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. Program ECM. After repair, go to next step.
- Review and record scan tool fail records data. Using scan tool, clear DTC's. Start engine. Using scan tool, observe specific DTC Information for DTC P0622 until test runs. If scan tool indicates DTC P0622 passed this ignition, system is okay. If scan tool indicates DTC P0622 failed this ignition, go to step 2 .
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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.