A while ago I fitted a 20xe afm to my C20xe engine to try and eliminate a long term fault where the engine would rev to 3k sometimes when started.
The 20xe afm has a pot for co adjustment where the closed loop c20xe afm doesnt have the pot.
Also the c20xe ecu which I have is not earthed on pin 20 where the 20xe one is to tell it that its open loop (no lambda probe) and to look for a co adjustment pot.
The early afm seems to have fixed the problem I had and yesterday I had the bonnet up (fav pastime of mine lately!) and the engine had a slight misfire at idle so I thought as I know its lean at low revs I would see if altering the co pot would richen the mix at idle and cure the misfire.
No sooner had I touched the co screw when the management light came on with code 65 or 66 cant remember off hand but it was low volts on co pot.
I refitted the other c20xe afm and out went the light.
I metered ohms across pins 1 and 6 on both afm's as this is the output from the co pot. The c20xe one was 387ohms and the 20xe one was 2ohms!
Now I can only suggest that the previous owner had altered the pot and that when I fitted it I was getting a high resistance across the pins 1-6 which satisfied the ecu to be within range and that when I disturbed it the reading fell to outside its range.
On the bench I cleaned all the 20xe afm pins and remeasured the resistance on 1-6 still 2ohms so wound in the pot till I got the same 387ohms reading that was present on the later meter.
I was under the asumption that the later afm/ecu took no notice of the pot setting but looking at the circuit I see that its still got the pot on the later one its just set at a fixed value and sealed off.
I have to assume as I dont have a co meter here that any adjustments made to the pot will not have any effect on the later closed loop system but you never know
Anyone like to measure between pins 1-6 on a working known good 20xe and c20xe afm and let me know what readings you get out of interest please.
I will refit the 20xe afm later just to se if that now works ok with no fault code lamp lit.