I recently adjusted my AFM 2 clicks leaner to try and restore so mileage to my truck but to no great success. After doing this my CEL came on giving me codes 23/24 fuel ratio too lean and too rich. I changed the O2 sensor figuring it was on the fritz now I get a code 21 but the other 2 are gone??? Is the sensor just faulty or should I reset the AFM to stock??

 

did you reset the ecu? unplug it when you did this so it can relearn the afm? cause you just confused the living heckens out of the ecu doing this lol


as for your code 21 dont know what it is try looking it up

 

code 21 is faulty O2 sensor or circuit, so no wonder the other two codes are gone. if it's a heated (4 wire) sensor, it's possible that one or both wires for the heater circuit are crossed to the sensor wire(s). regardless, recheck the connections. if you spliced in a sensor make sure the splices are good and clean. if it's a sensor with connector, make sure the connector terminals didn't push out of the connector.

 

Yes it's a heated 4 wire. It's on a 1990 4x4 pickup. I checked the connectors(its a direct replacement) and put dielectric grease in it to be sure, looked ok. checked the wiring, no breaks or green death. The light is out now but that's because I pulled the ECU fuse for a while, we'll see if it comes back. If it does return the o2 sensor??

 

depends on the codes.

 

Well I switched back to the old o2 sensor and code 25/26 showed up again, came on when I was on the highway. That damn orange light is starting to piss me off. This all started after I adjusted the AFM, I'm about ready to put it back to stock setting or get a used one.

 

if putting the stock setting in fixes the problem then changing from stock caused the problem, no?

 

Well I'll have to see I haven't put it back to stock yet. I've just never heard of anyone having issues when they "tweak" thier AFM's. I thought my truck was just being stubborn. I should've left well enough alone.

 

Well put it back to stock and no change same codes. I did take it on a trip yesterday and on the interstate averaged only 17mpg, not good.