Rick's Free Auto Repair Advice

Trailblazer no start

How to diagnose and fix a Trailblazer no start condition

If you’ve got a Trailblazer no start condition, first identify when you’ve got a blown fuse #28 (15A on the 4.2L engine and 10A on the 5.3L engine) in the underhood fuse box. A blown fuse #28 will cause a crank/no start condition because it powers the PCM and fuel injectors. Without power, the PCM will not energize the starter relay, so no power can flow to the starter motor.

This is a tricky one to diagnose because it’s so easy to get on the wrong track. You may think you’ve got a short somewhere in the PCM or fuel injector harness—and you may have that problem. But shops are also reporting that they’re finding loose ground connections as the cause. The loose ground connections cause arcing that flows the fuse. So start with the grounds.

Power runs on the pink wire to the fuel injectors, but the PCM completes the ground for the injectors. There are several grounding eyelets under the ground connectionintake manifold, so clean and tighten those first. Then check all other grounding points. If that doesn’t solve the problem, check for rub through points on the main engine harness around the motor mount areas.

If the problem still exists, check for short to ground in the power feeds to the injectors on the pink wire and to the PCM.

©. 2016 Rick Muscoplat

Posted on by Rick Muscoplat


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