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2005 chevy trailblazer_lt
7 Posts
Discussion Starter · #1 ·
Does anyone have the ability to update the PCM without going to the stealer? I would really hate to give them $100+ for flashing the PCM... Plus, anyone have the part number for the new cooling fan? 2005 TB 4.2L LT


Technical Service Bulletin #04-01-38-019A addresses all 02 - 05 T/B, Envoys, Rainers, etc. for poor A/C cooling efficiency following engine start-up, low speed driving and idling condition in high ambient temperature situations. This bulletin applies to all of the above vehicle built before June 2005. Certain vehicle built in June, 2005 already have had this update and those vehicles would have to be checked to see if the update has been performed. The update involves replacement of the electric cooling fan and a PCM recalibration.
The condition involves no-to-insufficient fan operation during these conditions. The A/C condenser and A/C compressor head temperatures rise and cause cool-down efficiency to suffer. While driving, air flow across the condenser is sufficient and A/C performance is good. The update commands additional fan speed operation at low engine RPMs and idle condition. Air flow across the condenser helps in heat transfer and lowers A/C pressures, hence cooler air. I have an '04 and we have been experiencing some warmer days of 80-85 degrees, sunny, but lower humidity numbers. Currently, my A/C system works great...I did do the PCM calibration as it was available at an earlier date (TSB 04-06-02-005).

· Banned
2004 gmc
26,436 Posts
A fresh PCMforless tune might have the new code in it. Email them. Certain independent GM mechanics that invested in tech tools and are up to date on their subscriptions can do it, IIRC. But none of them are going to be free. You might call around and see if you can find a GM dealer (doesn't have to be your brand vehicle) that will charge a fair price for ten minutes of work.

The new fan clutch has been extensively discussed. Start here:
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