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tcm won't allow 05 neon to shift out of 1st

Posted: Sun Jul 13, 2014 5:43 pm
by neon_newbie
My speedometer started acting up about a 2 weeks ago. I went to get it diagnosed at autozone yesterday because the engine light came on. TCM threw two codes: p0700 (transaxle malfunction) & p0720 (output speed sensor). I replaced the sensor & it worked fine until I started driving back home from down south, then the speedometer started fluctuating again, the light came back on, & when I pulled off from a stoplight, i was @ 30-35mph & it was overreving @ 4500-5000 rpms. It wouldn't shift from 1st or 2nd gear. I took it back to get diagnosed & it's throwing the same two codes. The sensor is brand new. Do I need to replace the TCM? & this may sound like a dumb question but would I need to let the TCM reset to configure to the new sensor? I mean reset by unhooking the battery. Or am I gonna need a whole new TCM with a new tranny? & if so, anyone know where I can get a cheap one besides salvage yards?

Posted: Sun Jul 13, 2014 10:32 pm
by sidepipe87
There is no TCM on a 2gn with a 4 speed, its part of the PCM. It may need a solenoid pack. I have an almost brand new one

Posted: Mon Jul 14, 2014 9:38 am
by chipdogg
Or I have a pcm, skim unit, and matching key chip (end is broken off key from when I tried fixing my sisters 04 and stuck chip next to non chipped key). Its all good, her car ended up having a broken wire from pcm to asd relay in harness. 50 shipped, been on my shelf for 2 years

Posted: Mon Jul 14, 2014 11:18 am
by neon_newbie
The reason I say tcm is because the first code says there is a transaxle control module malfunction.

Posted: Mon Jul 14, 2014 11:39 am
by chipdogg
Its all one unit, no separate ones in 2003-2005. Only 02 I believe. That one was bolted on passenger side if I remember right

Posted: Mon Jul 14, 2014 1:22 pm
by sidepipe87
^correct.

Posted: Mon Jul 14, 2014 3:08 pm
by neon_newbie
Okay. So then do I need to replace the entire PCM? & what is the rough estimate of the part? I'm hoping I can maybe find a decent used one from a salvage yard or I might just have to replace the entire trans since I can feel it slipping when it shifts into third.

Posted: Mon Jul 14, 2014 3:29 pm
by occasional demons
I would check the wire from the output sensor to the PCM/TCM just for the heck of it.

If it is slipping, then the PCM will see the incorrect output speed compared to the input speed. It could be a worn clutch pack. A worn clutch pack means rebuilding/replacing the ATX.

You may need to find a reputable trans shop to do a better diagnosis. For what you spend between us and you second guessing, and maybe not fixing the issue, it might be cheaper to pay for a hands on professional opinion.

See Chipdogg's post #3 as far as a salvage yard PCM. You cannot just take only the PCM. The VIN and SKIM codes need flashed to the used PCM to even let the engine start. More and more dealers are refusing to do this with used parts.

Even if you get a known good used ATX and put it in, there is still a quick learn procedure that needs done to keep for potentially damaging the replacement, since your PCM will be trying to shift it from the bad ATX's parameters.

I'm sure if you search the web for 41te / 40te quick learn procedure, you will find some info on it.

41te is used in the '01/'02 neons. '01 in the exports only. It is also found in some PT Cruisers. Boosted ATX PT's pretty much guaranteed.

You can use the '02 41te, but the solenoid pack might need swapped. The connectors might be different. Your 40te can be rebuilt to 41te specs, if you can find a trans shop that will accommodate you. The 41te has an extra clutch disk, and is a better.

Posted: Mon Jul 14, 2014 4:13 pm
by chipdogg
Where in Wisconsin are you?

Posted: Sat Jul 26, 2014 4:34 pm
by neon_newbie
I'm located in Milwaukee. and the few shops around here charge between $70-150 just for diagnostics, which is outrageous to me so that's why I came on here to narrow down the problem 1st since this site has helped me plenty in the past. a trans guy I know came in from out of town and lifted it to look underneath and turns out it was only a broken wire. it broke off right where the speed sensor connects. im really glad I didn't take it to a local shop to be charged $70+. Glad that's fixed ..whew.

Posted: Sat Jul 26, 2014 5:49 pm
by Midnight_Rider
If you have tranny issues, chipdogg is the right man for the job. :salute: