QuestionQUESTION: I have a 2005 Chrysler Town and Country. The check engine light has been on for a few months, to change an o2 sensor. I brought it in two weekends ago and had it changed out. The light went out for two days then came back on. After the light came back on it
started running rough. I brought it back to the shop this weekend and it turns out they were sent the wrong upstream o2 sensor and changed it to the correct one. The light stayed on for 2 days and has now gone out but the car is still not running right. Whenever I am at a red light it feels like it is going to stall but hasn't yet. Any ideas what the problem could be? Also I had a tune up done the weekend before I had the o2 sensor changed, could the wrong sensor have any effect on the coil pack or spark plugs?
ANSWER: Hi Kitty,
The wrong sensor would probably not have impacted the "tune up" because in fact while I am not sure what was done at the "tune up" there is almost nothing that can be adjusted on these engines as they have built-in settings/ability to self-adjust. The tune-up is typically just change the spark plugs.
What is the size of the engine (L)?
Have you tried turning the ignition switch: "on-off-on-off-on and leave on", doing that in 5 seconds or less elapsed time? Then watch the odometer window to see the mileage replaced by a 4-digit number(S) preceded by a P. Let me know any such numbers.
Other than a fault code number about the only item that can cause missing at a stop is if you have a vacuum hose leak which leans out the mixture too much at idle. So if you don't get a fault code, I would have the shop that did the tune up check over the vacuum hoses for leaks, at no cost!
Please read the PS below and respond to it.
Thanks,
Roland
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QUESTION: Hi Roland, thanks for getting back with me. They changed the spark plugs and wires or coils when the did the tune up. I brought the car into another shop yesterday on my way home from work and had them put it on their machine, they got the exact same code, for an upstream O2 sensor, nothing else. The light has since gone off but the car is not running right. I did not have this issue before they changed the O2 sensor,and only after the car recognized it was the wrong one, even with the old one that initially needed to be changed it did not run rough. I am going to bring it back into the shop tomorrow morning and will have them check the vacuum hoses. Can you think of anything else that might be causing this that I should have them check tomorrow?
Thanks so much
P.S.
I voted for you.
ANSWER: Hi Kitty,
Even though the light if off it now appears that in fact the O2 sensor is still being seen as at fault based upon the code readout. If you want to be certain that the code is not 'stale', then the battery needs to be disconnected briefly to erase an earlier code. If the garage yesterday did in fact do that, i.e. the sensor code is indeed 'fresh', then I would insist first the they look carefully at the sensor to be sure it is the correct one and second that they look carefully at the 4 wires that connect to the sensor as those are very fragile and the mechanic who put it in could have damaged it. Finally, if neither of those turn out to be the cause of the code, then they should check that the 4 wires at the sensor plug are indeed showing a good connection to the powertrain control module pins to which they attach and also that they are not shorted to a rouge voltage source or to a ground wire. I can give you the specific connection numbers they need to verify if you would tell me the engine size that you have. In checking the wires out the first thing to do would be to look carefully at the 4=wire "harness" between the plug and where it disappears into the larger wiring harness to be sure that there is no sign of melted insulation that could also cause this sort of a code.
In any case, since you paid them to deal with the O2 sensor they should get to the bottom of this without further labor costs.
Thanks for the rating and nomination, which you can do again if you so choose.
Roland
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QUESTION: Thanks again for the prompt reply. I will have them check everything you suggested when I bring it in tomorrow. The engine size is a 3.3 V6, base model.
Kitty
AnswerHere are the O2 upstream sensor connections from the plug of the sensor:
pin 1 black/light green goes to chassis ground
pin 2 brown/light green goes to pin 18 of the pcm and is the voltage supply for the heater
pin 3 brown/dark green goes to pin 32 of the pcm and is the sensor signal ground
pin 4 dark blue/light blue goes to pin 31 of the pcm and is the sensor signal output wire
These may prove helpful to the mechanic.
Roland
Thanks for the rating, and by the way you are entitled to do a 'nomination' with each answer.
