Brain fart. Disregard.

Yea it should but because it stays open loop, fuel trim and 02 voltage does not change. It runs car with computer base map. Thats my problem

I know. What value is the ECM seeing for the O2?

Here is an old trick:

Disconnect the single wire O2 sensor.......turn key to on, don't start.....observe O2 voltage....should be around 0.455 volts in data.... now take a wire and attach it the harness half going to the ECM, not the half going to the O2 sensor....

Now hold the other end of the wire with one hand, and with the other hand, touch your index finger to the pos bat post.....O2 data should approach 1.0 volt.....now move the index finger to the neg bat terminal and data should approach 0.0 volts....if you get these readings, then the O2 sensor/harness is bad.....

If you don't get these readings, there is a harness problem/ECM problem....

You CAN'T go into closed loop if the O2 sensor is not providing a varying signal....

Forgot to mention that it is usually the the coolant sensor or O2 sensor, OR the circuits to them, that prevent an ECM/PCM from going into closed loop....rare cases it'* the ECM/PCM itself.....

Sorry for delay i was on holiday.


I did not yet test 02 wiring but i connected tunerpro. 452mv is start volts of 02.

All went fine and 77f is temp when it should go closed loop (i opened that file to look temp) and now it went to closed loop. Full warm engine target afr was 14.71, 02 were moving approx 200-900mv all the time, maf was 5gm/sec on idle, BLM 116 and fine fuel correction 124. Thats bad? Supposed to be near 128/128?


I shut off car and started again. No more closed loop. It stayed in open no matter time. 02 was locked and blm/fine fuel too 128 both. Target afr under 13. Oxygen sensor was around 850mv. No big movement.


I didnt remember first that closed loop was working about 1 times to 20.


And ive been tried for four different 02 sensors and one is now in my c1500 chevy and working well.



Why closed loop blm and fine fuel was far from 128 and if its not 02 sensor/wiring is ecm only problem?


Maf cant do that? Ive tried tunerpro without maf and computer still counts air input ... So look a like working (increasing and decreasing by throttle/off) can cheat you?


First maf caused idle to go 800-1500rpm in hot engine and car was not driving soft in steady speeds. Those problems are gone.

Have you changed anything in the software?

Of course not! And i dont think its even possible with this software?

I just looked what ecm asks and needs but all fine there.

And how did you come to the conclusion that 77F is the set temp for closed loop operation?

I dont remember english term for that but its programmed to ecm.

And no matter that again, second start and others car did not go to closed loop no matter time and engine temp which is about 195f when engine is fully warmed.