Won't shift to 4th gear? P0843 ? "D" light flashing? Possible Solution!
 

2008 Base TL W/ 55,000 miles

Was going to spend the Saturday with my girlfriend who lives about 10 minutes from me. 3 minutes after picking her up my CEL came on and the navi showed code P0843.

I usually drive in sports shift for better gas mileage 70% of the time, but when this occurred I was driving the car in "D". After the CEL came on I noticed the rpms was steady at 3k rpms and wouldn't drop. I was traveling maybe 35-40mph.

I pulled the shifter to the sports shift to see what gear I was in. It said 3. I tried to upshift it to 4th but it wouldn't budge. No matter what speed I was (35, 40, 45). I tried slowing down to 20mph and downshifting to 2nd and it still wouldn't...

The only time it would downshift was when I would come to a complete stop than it would automatically go back to 1st gear and from there I was able to shift from 1st to 2nd, 2nd to 3rd, but still could not shift past 3rd gear...

After pulling into a parking lot and doing a quick search about the DTC P0843 I ran into a acurazine member who said it's most likely the pressure switches.. Swap them out and you should be good.

After grabbing some lunch, I dropped my girlfriend off and went back home and me and my pops got to changing the pressure switches (I purchased the pressure switches nearly half a year ago to do for preventive maintenance, but never got around to doing it. Didn't think I would have any problems with it since I only had 40k miles at the time). I used this guide https://acurazine.com/forums/3g-tl-2004-2008-93/110-b-diy-guide-replacing-3rd-4th-gear-pressure-switch-3g-tl-2007-2008-a-840630/

Changed the 3rd gear pressure switch first (the one accessed through the wheel well). Thought that was the problem, so I put the tire back on and went for a test drive. Still the same problem. Wouldn't shift past 3rd. Tried resetting the ECU using the pedal method and still the same problem...

Drove back home and proceeded to change the 4th pressure switches... Next up we decided to do the one on the back of the transmission, the one located under the front strut bar under the hood... Upon inspection it was obvious what was causing the problem.... This is what we found upon removal

http://img823.imageshack.us/img823/5...0414202306.jpg

http://img96.imageshack.us/img96/755...0415103042.jpg

http://img138.imageshack.us/img138/4...0415103106.jpg

The 4th gear pressure switch located behind the transmission was BROKE! How in the hell?

To sum it up, replaced the remaining switches (new 3rd gear, new two 4th gear pressure switches) and went for a test drive. Still had the problem. Decided to pull over and try the pedal ECU reset method again. As soon as I started the car and drove it shifted into 4th and 5th without a problem. CEL remained on. Plugged in my ELM 327 OBD2 bluetooth scanner and used my torque app on my cellphone to reset the fault codes on my ecu. That worked and CEL immediately turned off.

Tried scanning for anymore codes after it turned off and 0 faults came up. Drove for about 20-30 miles after getting it fixed and still no problems so far.

It's funny because I called up the nearest Acura dealership after eating lunch and asked them about it at 1pm. They said the earliest appointment was 3PM and I said OK. I told them what was happening and the DTC code. I got a call back later saying that the tech won't be able to fix it by today, and they had no loaner cars to give to me so I should bring it back monday. Monday was not a option because I have class 35 miles from home, and I was not going to drive 35 mph all the way to class... It would take me 1 hour and 30 minutes.

I asked the lady to have the actual tech call me to talk. He calls and I ask him about the problem and tell him that I think it's the pressure switches and I already have them in my trunk, just never got around to installing it. He says he wanted to thoroughly diagnose it before changing the switches because of what I 'suggested' over a 'phone conversation'. Told me to bring it in early Monday morning and it would take him 1 hour - 1 hour 30 min to diagnose it.

Ended up saving myself at least $100 and some time :thumbsup:

First, glad it's fixed. Good thing you checked all three switches. Sounds like you might've got a little lucky in that it was clearly a broken switch. The Reset after changing switches is good info too.

:thumbsup:


Eh, not for sure. The trans is part of the 6-year/70,000 mile Power Train warranty, so you should've been covered with no charge.

Now whether they could properly diagnose and correct the problem without throwing a rebuilt trans at it is a whole other question.





Finally, is the girl in this video your sister?:



:tongue:

Rofl thanks. But yeah my car is a salvage title so all warranty is expired and I would have to pay out of pocket for everything.

lmao and I just noticed what I said doesn't make sense... 35 miles @ 35 mphs = 1hr 30 minutes hahahah. It should clearly be 1 hour.

My excuse is that I usually drive 70-75mph cruise control to class and it takes about 40-45 minutes. Since I would have to travel at half the speed, I just doubled the amount of minutes lol thanks for pointing that out :thumbsup:

Asian; can't be :rofl:

Glad everything was solved!

not really. just a few minor things.

replace pressure switches every 40-50k or 3-4 years.

replace OEM ATF with redline mixture 3x3 drain and fill.

that's about it...and your car will thank you afterwards.

Motor mounts going bad are common issues. Correct me if I'm wrong.

Anyone get this code lately? P0843? I have the same exact symptoms as the OP. Mine's an 07' Type S with about 95k miles on it now. Just happened today and it will not shift in to 4th gear. I'm ordering the press switches from the 07-08 DIY and hope that'll clear things up. This car has had a lot of work done to it since I've bought it already, hope this works :wish:



And yes they are, two motor mounts were replaced along with two axles in Sept with 94k miles on it. I'm praying the trans is alright and it's just the switches.

1200+ miles and no issues yet. Replacing the 3 pressure switches seams to have worked.

Just curious, anyone else get this trouble code before?

Digging out a 5 year old thread. I was blessed with this just today at 155k. Hopefully that's all it is since I gambled on some non-oem sensors the first time I think I'm paying the piper now on it. 3 new OEM sensors are on the way. Ugh.

^yep, OEM sensors or bust

And, job done, ecu reset, everything looks good so far.

This exact thing happened to me about 2 weeks ago.

I replaced my switched just because, at 125k... not knowing the 4th gear switches I had used were aftermarket. Put new OEM in, all my issues went away. I've done 2 drain n fills... car is completely different. Feels great.

I hear you, the switches gets pricey since there are 3 on a 07-08 TL-S, and I gamble also with aftermarket too but not today I ordered sum switches from Benny V. OEM for sure