Hi Guys,

long time lurker, first time poster :)

As the tittle suggests, I'm chasing a Code36 in my 1987 Corvette, which is a MAF Burn Off error

I purchased the MOATES ALDU + CABL1 and loaded up Datamaster software and it all worked so easily.
So a big thankyou to those guys for their product.


I’ve found the following information:
The ECM waits 5 seconds after ignition-off to start the MAF burnoff. The burnoff lasts 1 second. The ECM shuts down 11.3 seconds after ignition-off. The burnoff test starts 0.3 seconds after burnoff starts. The ECM make 6 voltage measurements and all 6 must be within the voltage window to pass the error code 36 test. On my car that window is 0.4 volts to 1.90 volts.

However, the data I’m getting out of the ECM doesn't reflect that.
Even though I can SEE and hear the burn off take place the data doesn't seem to be getting to the ECM. (or incorrect data is).
I've done all the trouble shooting as per the Factory manuals and bulletins and its all as it should be, but the code persists.


Code:
 

Time Stamp
Ign Volts
RPM
FP Volts
AFGS



Secs
Volts
RPM
Volts
gm/Sec



41.128
13.7
775
13.6
9



41.256
13.6
800
13.6
9.3



41.384
13.7
775
13.6
9.2



41.512
13.6
775
13.6
9



41.64
12
925
13.6
8.9



41.768
0
925
12.2
8.3



41.896
0
0
12.4
6.7



42.024
0
0
12.1
5.1



42.152
0
0
12.4
4.4



42.28
0
0
12.3
6.8



42.409
0
0
12.2
7.2



42.521
0
0
8.6
23



42.649
0
0
0.6
23



42.777
0
0
0
23



42.889
0
0
0
23



43.001
0
0
0
23



43.113
0
0
0
23



43.225
0
0
0
23



43.337
0
0
0
23



43.449
0
0
0
23



43.561
0
0
0
23



43.673
0
0
0
23



43.785
0
0
0
23



43.897
0
0
0
23



44.009
0
0
0
23
The above data shows when I turn off the ignition switch and you can see the rpm drop to zero, then you can see when the fuel pump relay goes to zero volts, but the MAF output (AFGS) goes to “23” and stays there.
It should record the burn off “voltages” as this is the input from the MAF to the ECM.
I didn't show all the data (post 5 seconds after shut down) as it doesnt change at all from the last line

My question is:
Are you aware of any impediment or changes that happen to the OBD1 connector in the vehicle once you turn off the ignition?
Does it “lose power” of some type which means I can no longer see what the ECM is seeing?
Do you have any idea why it goes to “23”?

Thanks for your help