lost on code 21

[sexygomer]

i keep coming up with a code 21 in my '85 lebaron t1. i've checked all the descriptions i can from it and i get: Neither rich nor lean condition is detected from the oxygen or sensor input. or Oxygen sensor input voltage maintained above normal operating range. so first i simply replaced the O2 sensor (under warranty, no biggie) still got the code, replaced the plug to the O2, still have the code, i can see it on my A/F guage staying in high (rich) for a while then it will adjust it for a few seconds, then settles back at high. Im gonna check the whiole wire under the hood tomorrow just to make sure there's no short there. any suggestions would be great. it's killin' my MPG:thumb: thanx

[Stevien1]

Yep, check the wire all the way back to the LM. I hope you didn't use a Bosch O2 sensor- their quality is non-existant.

You might want to check for things like clogged air filter, bum FPR, or MAP sensor/vac line issues.

[turbovanman²]

If its stuck rich, its not the ox sensors fault. Check why its running rich. Bad coolant sensor, FPR, injector etc.

[sexygomer]

i checked the wire as far back as i could, lokked 100% to me. i am using a Bosch part however, but i've never had a problem b4. i also checked for bloackage in the swingvalve and nadda. i'm gonna try a new FPR for shits and giggles. if that dont work, i'll try a different brand i suppose thanx

[iTurbo]

I have just went through this exact issue with my Spirit R/T. In my case what would happen is the O2 would randomly read very high upon startup 3v+ and the A/F would be pegged rich. I checked with my OTC scanner and it was at that exact moment I would get code 21 stored. The O2 volts would slowly drift back down to the normal 0-1v operation and it would go into closed loop (bounce) Even when in closed loop, the A/F gauge had a strage bouncing strobe effect, and the O2 volts would never hold still at WOT. It would sporadically read .80-.92v at WOT.

I was pretty convinced it was the O2 sensor. At first I couldn't find anything wrong with the wiring. Then I removed the friction tape that covered the O2 sensor harness and found the wires were fried! You couldn't tell by looking at the friction tape that covered them, but the wires were burnt to a crisp the insulation was cracked enough that the circuits were shorting out with each other!

So about an hour ago I got done replacing the entire O2 sensor harness and rerouted it up along the top of the firewall and zip tied it to the main harness. Now that it's further from the exhaust/turbo, it shouldn't melt again. I took the car for a drive and could immediately tell the difference. It drives smoother and the stuttering problem it had during cruise seems to be gone. It's no longer reading crazy high voltage at startup. WOT is a rock solid .98v.

So basically you should check your wiring very closely.

[MiniMopar]

Code 21 means the signal is getting stuck in the neutral region too long (around 0.5V). This happens when the connection to the sensor becomes open. The Logic Module lightly holds that input at 0.5V so that if the sensor becomes disconnected it won't fly all over the place and make the LM think it is getting a signal when it is garbage.

The sensor has a low enough output impedance to overcome the 0.5V that the LM holds the input to and will drive the input wherever it needs to between 0 and 5V.

Bottom line: code 21 means you have an intermittent between the LM and the O2 sensor element. It could be the sensor itself failing, but more likely it is a wiring issue or possibly the LM itself.

[sexygomer]

fixed it, it think it turned out to be a (well two) crappy O2 sensors. Purchased a non-Bosch and it work just fine now. thanx all