CAracer

I just had my trans replaced under warranty. It has less than 100 miles on the new trans. The engine service light comes on while cruising at 80 mph, with the cruise control set. There is a slight feeling that the trans is down shifting while climbing a slight grade. After this happens, the Service Engine Soon displays on the DIC. This is the same message I observed with the last trans, which expired. It's also displaying this code P 1870 CH. Once this code is cleared, the trans works fine again.

It also appears that the line pressure is very high. While driving on the street, the car shifts very violently with very little throttle input. Basically, under very little load.

Does anybody out there have any ideas? The car is a heads/cam car with some programming.

Appreciate any help or input you guys can give me.

Thanking you in advance. :confused: :confused:


[Modified by CAracer, 2:06 AM 6/14/2003]

Colbalt Blue

The SES light is associated with your enviromental controls i.e. O2 sensor, EGR Valve, cats and so forth.

check you codes and post them. One of the members will have an answer for which codes have been se.t

WWK888

You might want to check your trans fluid level...it has to be right on otherwise the shifting will be erratic.

CAracer

The trans was just installed by the dealer 100 miles ago. I'm sure they topped off the fluid. Besides, the old trans removed with only 12,500 miles, displayed the same message and code. Please read the post more carefully.

Service Engine Soon is displayed on the DIC. The SES light does not come on.

I'm pretty sure it's programming related. I was hoping that someone who does programming would chime in. :confused:

WWK888

I did read the post carefully...I realize it could be a programming problem. All I am saying is dont overlook the obvious things first. If you trust your dealer that much then fine. Im sorry I responded.

CAracer

William, I do appreciate all comments. However, this was the same issue with the trans that just went out with only 12,500 miles. The dealer installed the new trans under warranty. I was lucky to get a new transmission with all the mods on the car. The trans was installed by a experienced mechanic with over thirty years experience. I would have to assume that he filled up the trans to the proper levels.

I was just hoping that someone out there has had similar experiences with other A-4's. Thanks

WWK888

No problem...the reason I responded was that I had almost the same situation with my Camaro SS. It was throwing codes and not shifting correctly after a torque convertor swap. The mechanic (dealer) swore he topped off the fluid properly...but he didnt. He was about a pint short. Once that was corrected everything was fine. Good luck :cheers:

98GreenC5

1870 is a TCC slip code, test for slip is run when TCC is engaged,
Common causes are: low transmission fluid , gear change ie,273 to 315 and
ratio not corrected in PCM or worst case, bad TCC.
Don't discount low fluid, this has been the cause of many 4L60 E problems.

The max pressure shifts are the result of the 1870 code as you have noticed.
the code is trying to prevent slippage and more damage...........................

Dick

Kenny94945

CA, I looked up this code in the manual.
The very first step is to confirm the tranny oil level.
Let's get that done and out of the way.

Without you car here, it appears the "crux" of this code is the Torque Convertor Clutch.

The test procudres for this code appears quite time consuming and dare I say complex.

Since the tranny was changed out, perhaps some of the accessory or attached parts were not and that is why the problem has reappeared.

The two main culpruts refered to are:
1- Torque Convertor Clutch Solenoid Valve
2 - Torque Convertor Clutch Pulse Width Modulator

Further, it states that this code will set high line pressure, so you are onto that correctly.

Additionally, it states that internal transmission failures may set the code.

In that regard look to internal shift solenoid 1-2 and solenoid 2-3.

Now go check your oil...trust no one on this but yourself. That is the easiest fix.

CAPN17

The first thing I learned about my Vettes is never trust others to do the work right, always double check it yourself. Better yet learn how to do the work yourself, then you will have a better feel for the problems.

ToplessTexan

What kind of mods are we talking, just H/C + programming? Has it done this since programming?

MikeyD

No.1 Check fluid.
No.2 Check switch behind the brake.

I have just had my tranny replaced with an FLP level 4 and also a Yank 3000 converter. After getting the car back, I had all sorts of TCC problems. Sometimes it would lock up and other times it didn't. When it did lock up, it kept throwing the P1870 code which someone before had mentioned is the tansmission slip code. There is a switch behind the brake pedal that sends 12 volts to a pin on the PCM which is the TCC lockup command. When you depress the pedal, it breaks that 12 volts and the TCC will disengage. I adjusted that switch and now I have no problems with the TCC locking up. And, I haven't gotten that P1870 code yet either. It makes sense about the TCC lockup issue but I'm not sure why that switch would have anything to do with the slip code :confused: Its only been one day so I'm definitely not going to say that was THE fix but I certainly hope it was!

ToplessTexan

Very cool if that's the fix. I thought that was a great suggestion but hadn't wanted to be too optimistic since I don't see how that might explain the code.
:thumbs:

Mike Mercury

CAracer

you also need to read others posts; they are making some very valid points based on experience.

very valid. There is a special and unique method to do this... that applies to C5's only. Just because the dealers mechanic got your new tranny installed... doesn't mean he is knowledgeable about the C5 "special" tranny fluid level check method.

that is spoken from experience with C5's :thumbs:

:nono:
there's that "assume" word :)

and that is who has been posting replies to your questions. When the PCM detects unusual slippage in the drivetrain (on A4's) it does raise the line pressure to compensate. If you are getting those hard and neck-jerking shifts at even light throttle... then there probably is not any real "slippage" but the PCM is being fooled into believeng there is.

The most common reason for the 1870 code is that the PCM is programmed for the wrong rear axle ratio (or there is real slippage due to a part failure).

If your C5 still has it's factory rear axle ratio; then there may be a real part failure... or the dealer reflashed your PCM (without your knowledge) with the wrong rear axle ratio information.

there is a speed sensor in the tranny as well. Some things to find out are:
* if the sensor is electrically connected; and
*whether the sensor was damaged during the swap.

Plus keep in mind that even thopugh the tranny was replaced, the error code will continue to show for a couple hundred miles unless it has been successfully cleared out by someone that knows how to do this properely.

First things first... make sure the tranny fluid level is full; using the check method that is specific to the C5.




[Modified by Mike Mercury, 10:34 PM 6/6/2003]

WWK888

Keep us updated...

Aloha
Bill

CAracer

First off, I want to thank everyone for their excellent recommendations.

I did have recent programming and the problem started shorty there after.
Also, on the the low trans fluid theory, I will check this out in the morning. However, the last trans I just replace was doing the exact same thing before it went out. The same code and mechnical hard shifting under light load as the new replacement. I guess it is possible that the old trans was low on fluid as well.

Thinking back, when we did the heads/cam install, we lost some AT trans fluid. I had another shop check it and top it off. Is it possible to have the same problem back to back? Two transmissions in a row???

The rear gears have been changed to 3:42's and the car was programmed for that over two years ago without any problems. I don't believe the dealer re-flashed the computer because the idle, shifts points and other properties are still working as they were prior to the trans install.

Mike, you said that the error code may come up again unless it's successfully deleted. Can you tell me how to do this? Funny thing, once I clear the 1870 code, using the option and fuel button, everything works well. It appears that on the highway, when cruising at 80 mph, is when the code rears its ugly head. It's like the converter is locked up and the slightest grade causes a noticable change similar to a light downshift feeling. Following that, the service vehicle soon appears on the dic.

The good thing is that once I clear the code, the line pressure goes back to normal and the trans seems to operate normally.

So again, thanks for all the great information. Any other thoughts are always welcomed.

Thanks CAracer




[Modified by CAracer, 1:02 AM 6/7/2003]

ToplessTexan

Any other correlated events? If not...

Okay, that's good. Same folks that did your gear programming did this latest round or no?

This is the expected behavior. Once PCM decides it's slipping, it codes and commands D2 line pressure which is where your hard shifts come from. Clearing the code sends things back to a normal state (although you haven't changed any of the conditions that triggered the event) but as soon as the PCM decides it's slipping again you're back to where you were. I wouldn't actually kill the code w/o understanding why it's throwing.

My feeling is that anybody experiencing P1870s and suspecting programming (particularly new programming) should get after it with the OBD-II scanner in order to verify the programming is correct. It's a very easy thing to rule out (or not.)

ToplessTexan

:confused: :confused: :confused:

Kenny94945

After the oil check .........the TCC Brake Switch is another good one to focus on....for the easy fix.

There is a great Scan Tool discussion on the torque converter clutch on pg 7-67 to 7-69 in a 1999 factory manual (in addition to the specific code diagnosis).

Good luck; I think we would all like to know it was a $1 part you repaired with the forum's help. Please post the answer once solved.


[Modified by Kenny94945, 8:37 AM 6/7/2003]

ToplessTexan

Do you mean the data definitions or something else?

$1 part would be cool, if it were me I would not be so lucky... :(