Chrysler Repair: Transmission slip while braking to low speed, 1st gear., dodge avenger, o2 sensor

Question
QUESTION: Hi!

I have a Dodge Avenger 2.5 V6 automatic (A604/41TE). And since I bought the car in June I have allways had trouble while I am braking to a low speed and then take off, heres what happeneds:

If I start up the car one morning and drive away, everything seems to be working perfect. But when the car heats up a little bit something strange happeneds to the transmission. When I get to a stoplight I must obviously brake, and when I reach a low speed and try to take of directly, the car slips at first gear and the engine RPM jumps up to 900 and lowers to 300 rpm. The car never slips if I come to a complete stop, but if I brake a little bit to a speed of 10km/h and then takes of, the car slips, very annoying =(

Hope you can help me.

PS, the engine RPM is pretty low sometimes, after the car has warmed up. I have a O2 heater circuit issue on one of the 4 sensors.

Thanks in advance!

//Jonathan / Sweden

ANSWER: If you have identified by fault code a engine function issue, then I would deal with that first, as engine rpm problems can cause issues with the transmission's shifting. Also check for any fault codes that might relate to the transmission (in the 700's and 1700's). Let me know if you get any along those numbers. But first replace the O2 sensor, or at least see if the heater supply wires show 12v to be present and if so then replace the sensor. The sensors come into play only after warm-up so the onset of your problem then is indicative too that you need to deal with that. The transmission issue is most likely that it defaults to 'limp in' mode as a self-protective option when it sees a problem. In that mode it only runs in 2nd gear.
Roland

---------- FOLLOW-UP ----------

QUESTION: Hi!

I have replaced one O2 sensor (fault code P161) but now got a new fault code P141 (I think so).

The transmission works fine all the time, it shifts throw all gears (1-4). It just slips when I de-accelerate and then accelrate again (at the speed of ca 10km/h).

Do you think that may a speed sensor on the transmission?

Best regards
Jonathan P

Answer
I would verify the fluid level in the transmission. Then watch for new codes which I believe would be set when you have slipping. There are codes for exactly that and for the failure of the speed sensors. So let the codes be your guide rather than throwing parts at the problem in the hopes of getting the right one. The 141 says there is a heater issue with the downstream sensor on the left (front side) bank exhaust pathway.
Roland