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RussMasterTech, ASE Certified Technician
Category: Chevy
Satisfied Customers: 791
Experience:  19 years of GM Dealership experience. ASE Master with L1 and GM Master Certified in Electrical
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U1255-c0305-c0306-c0321 2004 trailblazer codes

Resolved Question:

u1255-c0305-c0306-c0321 2004 trailblazer codes
Submitted: 8 years ago.
Category: Chevy
Expert:  RussMasterTech replied 8 years ago.



Which module did you pull these codes from? Have you charged the battery and got it running since? There are some codes that will set when there is a low voltage concern.



Customer: replied 8 years ago.
I pulled codes with my scanner obdII global. I jumped the truck and drove last night 45 min.drove to job 30miles all ok drove home trans started shifting hard scanned it 5 codes u1255 twice,c0305, c0306,co321, I cleared codes checked all plugs and fuses let truck cool test drove 20 miles twice so far no codes
Expert:  RussMasterTech replied 8 years ago.

I would ignore the codes for now. Is it still shifting hard? The codes you gave me aren't found in the pcm. You'll need to scan the pcm and see if there are codes in it. Usually a hard shift is due to a code setting for the trans, but as I just stated, the codes you gave me weren't from the pcm.


Let me know.

Customer: replied 8 years ago.
thank you I am trying to find out IF I caused the codes from [email protected] trans or rebuilding trans or if the issues arent mine
Expert:  RussMasterTech replied 8 years ago.

If you ever get any PXXXX codes in the pcm. just let me know. I can always look up the diagnostic charts for you.


Best of luck. Hope your overhaul was successful.


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