[420blazer03]

Driving along yesterday and a code popped up. I scan it and it says something about coolant temp too low. Whatever, its a cold morning, reset.

today Im driving along and the check engine light pops up again. I scan it, and now it gave me three codes:
P2800 - trans range sensor
P0040 - O2 sensor signal swapped (???)
P0029 - exhaust valve control
I have no idea what any of these mean. The truck drives good for the most part, the transmission acts weird sometimes but I just chalked it up to 4l60e activities. It is a 2003 Blazer 2wd with the 4.3, 127k miles. Any help would be appreciated!

 

[420blazer03]

Here is a screenshot of my bluetooth obd2 reader

 

[oldeerslayer]

I'd try a different scanner. Those codes are weird. The 0029 code is for a valve your truck doesn't have. P2800 is for the PRNDL switch down on the side of the transmission where the shift linkage enters the case. The 0040 is for some crossed up O2 sensor wiring. Doubt seriously if that all happened at the same time while just driving along. If it's not the scanner then it sounds like your PCM is going wacko. These guys have a good rep:

S10 Blazer 2003 Engine Computer ECM PCM 12581565 4.3L - Programmed to your VIN # | eBay

This ECM will fit the following application 2003 CHEVROLET BLAZER V6 4.3L Engine (with ECM # 12581565). 2003 GMC JIMMY V6 4.3L Engine (with ECM # 12581565). GM used 3 different engine computer part numbers in the above application.

www.ebay.com

Double check the service number on the PCM because GM used a couple different ones in 03 S-series vehicles with the 4.3L.
Before dropping the big bucks look over the wiring under the truck for chaffing or exhaust heat damage.