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2004 chevy trailblazer_lt
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How long have you owned your TrailBlazer, what is the current mileage, and have you ever replaced the ignition switch?
 
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· Premium Member
2004 chevy trailblazer_lt
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3,439 Posts
The ignition switch is known weak spot on these vehicles. When they fail all kinds of electrical gremlins can occur all. Things from the radio turning itself on or off, changing stations by itself, different lights going out and then coming back on, etc. Normally the ignition switch is diagnosed by ruling everything else out or by how weird the electrical problems are.

Here is a how to on how to change out the ignition switch by yourself:


Also, do not cheap out on the new part. Please stay away from the Amazon & ebay parts that are priced in a too good to be true fashion and avoid most auto part stores house brand. "Forum favorite" ignition switches have the following brand names - ACDelco, NAPA Echlin, Delphi, Standard Motor Products (non T series) or BWD *non P series). Also, the cost of the part ranges from about $15 on Rockauto.com to about $40 for one of these brand's switches.

The relevent question for these switches is not if they will fail, but when they will fail. I personally keep a spare one in my glove box.

Good Luck!
 

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2002 chevy trailblazer_lt
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2,163 Posts
Aftermarket radio

The reason I asked that is to establish if it is possible for there to be a backfeed somewhere to the power lines that feed the ignition coils and fuel injectors.

You see, while there are many many stories of ignition switches having poor contacts and causing devices to NOT work I have never heard of ignition switch contacts remaining closed while the switch is turned off.

Indeed, having taken these ignition switches apart piece by piece I cannot envision any contacts remaining closed when the switch is OFF.

Your ignition coils and fuel injectors all get their operating positive power through the ignition switch. So if the key is turned off there should be no way for the engine to keep running. UNLESS someone crossed up some power wiring when imstalling aftermarket accessories and 12 volt positive power is feeding the coils and injectors through some mis-wired non-factory wiring.
 

· Premium Member
2004 chevy trailblazer_lt
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3,439 Posts
Good point, thanks TJBaker! Always nice to learn more from you!
 

· Registered
2007 chevy trailblazer_ls
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73 Posts
You may have something as simple as a sticky relay.
Next time it happens open the hood, pop the cover off fuse box and tap the relays. If it shuts down you've found the issue.
Otherwise replace the ignition switch.
 
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