Error Code 21

OK....I was driving the other day on the Expressway. I was driving up to expressway speeds from the entrance ramp when my JGC '94 V-8 acted like it was losing power. I stepped on the gas more and it quickly reacted and came up to speed. Then the check engine light came on. It drove good after that. Once home I checked the error code lights and found an ERROR 21 - O2 Sensor Voltage. Does that mean that I need to change it? And if so about how much will it cost to do it myself? The code stated that once the error code happens the O2 sensor goes to a closed loop operation until it has been fixed. It no longer gets the signal from the sensor until it is cleared. Would a O2 sensor that acts up cause the engine to shudeder and lose power like that? There are no other codes in the unit except 12 for a battery change about 4 months ago and the 55 which is end of codes.....Any suggestions?

FF/EMT Gary
esfd455

You could have a bad 02 sensor they run around $ 50 -60. If it hasent been replaced in 50 k it should be changed. It is really hard to tell if it is bad or if there is another problem withoout accessing the Data with a Scan tool.

It doesn't get info from sensor in open loop. After engine has run for a few minutes and reach operating temp, then it goes into close loop. When in close loop the computer is looking at all the sensors. The O2 sensor code could be set because of running bad. Most of time O2 sensor just cause bad gad milage, poor perfromance, minor drivablilty problems.

OK....I was driving the other day on the Expressway. I was driving up to expressway speeds from the entrance ramp when my JGC '94 V-8 acted like it was losing power. I stepped on the gas more and it quickly reacted and came up to speed. Then the check engine light came on. It drove good after that. Once home I checked the error code lights and found an ERROR 21 - O2 Sensor Voltage. Does that mean that I need to change it? And if so about how much will it cost to do it myself? The code stated that once the error code happens the O2 sensor goes to a closed loop operation until it has been fixed. It no longer gets the signal from the sensor until it is cleared. Would a O2 sensor that acts up cause the engine to shudeder and lose power like that? There are no other codes in the unit except 12 for a battery change about 4 months ago and the 55 which is end of codes.....Any suggestions?

FF/EMT Gary
esfd455

Did you figure out what your problem was?
I was having the same code pops up after the engine warmed, no performance problems tho, just the annoying CHECK ENGINE light, my problem was the wire that goes to the PCM from the O2 Sensor (K41, BLACK/ORANGE wire) was broken.

Did you figure out what your problem was?
I was having the same code pops up after the engine warmed, no performance problems tho, just the annoying CHECK ENGINE light, my problem was the wire that goes to the PCM from the O2 Sensor (K41, BLACK/ORANGE wire) was broken.


OK finally changed out the O2 Sensor. What a time with getting the connector apart and back together. The sensor came right out when the pipe was cold. The connector was up over the right side of the exhaust pipe and transmission. Could not get my hands/arms up there to disconnect or put the new one back together. Finally had to go behind the engine from above to get to it. Took 15 minutes to change out the sensor but 45 minutes to figure out how to put it ( the connector ) back together. Then I changed out the gas filter. Well I think the problem was there for my hesitation. The filter when I blew thru it with air was hard. The new one was like there was nothing there. I finally drove it and "WOW" what a difference. The filter was easy to change out. Used the plastic clips from the old filter for the connections.

Now do I have to clear out the error code from the memory for the sensor to work again? That would be disconnecting the battery for a period of time. Also does the memory for running parameters have to be reset by driving so many miles after the battery is disconnected. What do you think????????? Any feedback??????

Thanks,

FF/EMT Gary