Why don’t you put the old MAF back on and see what you get at the 1-2 shift point. Another thing you can try Is disconnect the MAF then start the truck and see if it runs better. It should switch to speed density mode and use the map sensor et Al.

What are your fuel trims with the MAF installed?

Anytime you get a sensor code you should test the wiring, power and ground before replacing the sensor. If you have an incandescent test light we can test the B1S1 heater circuit to make sure the sensor is getting proper heater power.

Its hard to figure out where random wires originate. You could follow the wires backwards in the harness to see where they start. Are there any other codes or things not working on the truck?

An exhaust restriction can cause the engine to breathe poorly at full output, is the cat new in that exhaust system?

Those grounds are really important, all kinds of problems can start if they are not really solid. Measure the voltage from your attachment point/braid/cable to the battery negative post with everything on and running. Should only read a few tenths of a volt or less.

Why do you want to swap the ECM?

What we’re the brands of those fuel pumps? Once again check the wiring before condemning a sensor or load.


George

 

My blazer is not running and maf reading 0.3
map= 29.8
Spark adv=18.5
Calc load=0.8
Stft b1s3=99.2
02s b2s1=0.165
????????

 

Sorry I just saw your reply I'm reading it now

 

You need 4 numbers for fuel trims:

https://blazerforum.com/forum/2nd-ge...-trims-102906/

A single O2 sensor voltage has no diagnostic value:

https://blazerforum.com/forum/2nd-ge...82/#post733375

George

 

Also looking at sensor values in live data does have value to do a first level sanity check against ambient conditions (ECT, MAP, IAT, BARO), or expected behavior (tps full scale movement). With key on engine off compare your MAP pressure to the published atmospheric data for where you live. Same with ECT on a cold engine.

George