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2002 chevy trailblazer_ls
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2 Posts
Discussion Starter · #1 ·
Hi
I asked this same question under a much earlier thread - but thought it best to try this with a new thread. I get the codes above (C0305 - Front propshaft speed sensor, C0306 - Motot A/B ckt malfunction and U1255. The vehicle cyl 1 misses and I can't figure out what the issue is. Replaced the ignition coil, new plugs, move plugs and coil around and the #1 cyl still misses and the codes just come back. So, what does the group think the problem is here - or do I just go to a Chevy dealer and have them diagnose the problem(s)?
 

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2003 chevy trailblazer_ltz
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8 Posts
I had issues like this earlier this year giving mine a tune up. A video said it had something to do with me disconnecting the battery and the computer thinking it's dirty or something I wasn't really sure,

But, after cleaning the throttle body and reconnecting the battery the computer reset and everything went back to normal.

Checkout u tube that's where I found the video. I faintly remember having to reset the computer somehow.

Sorry I couldn't be more help but that sounds like the problem I had. I even changed coil packs,
 

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2004 gmc envoy_slt
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2,638 Posts
If the misfire does not move with moving the coil or changing plugs, the problem could be a bad injector or a valve issue. Do a compression check on all cylinders to determine if cyl #1 has good compression.
 
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