Looking for C-5 tech or someone the help with a transmission problem I'm having with a 2000 C-5, (A-4, 3.42's). A little background:

About 18 mo ago the GM battery case cracked and leaked all over the PCM and wiring harness.

About a month ago, I got a check engine light and the DTC is P 1870.

First attempt to fix this by the dealer ended with a "cannot duplicate customes complaint." They simply cleared the computer and sent me on my way. The check engine light and the same code (P 1870) was set within 45 miles and I brought it back to them.

The second attempt the dealer replaced the transmission and torque converter. I got about 45-50 miles from the dealer again and the check engine light and P 1870 was back. By this time I have been without the Vette for about three weeks and I was in serious "Corvette withdrawl" so I drove home (about 150 miles) after calling the tech to confirm that I wouldn't burn anything up doing so.

I have been looking in the service manuals and I am wondering if this is a computer (PCM) problem or maybe a wiring harness that has been eaten by the spilled acid. Since my car has a set of 3.42's and a custom PCM program (from MTI in Houston), I don't know if having the dealer check out the electrical gremlins is wise. If GM wants to re-flash the PCM the MTI program would be gone and the 3.42 gears would mess up the speedo etc. and it might open up a can of worms like invalidating the extended warranty.

HELP!

 

This may be what you are looking for
http://forums.corvetteforum.com/zerothread?id=382714

or http://forums.corvetteforum.com/zerothread?id=245019


[Modified by MilYellow02, 7:01 AM 10/28/2002]

 

Can you use AutoTap or other scantool to monitor parameters as I mentioned in the first thread MilYellow02 pointed you at? That's the easiest way I know of to determine whether you have a programming or component problem which is the first problem solving step you need to take. Given that the dealer has replaced the trans and converter, I would be leaning toward a programming issue. This could be confirmed or denied with the PCM trace. (Reflashing or replacing the PCM at the dealer would definitely result in this sort of problem.) How long have you been running these gears w/o trouble?

 

I don't have AutoTap or scantool, I am hoping the dealer will be cooperative in diagnosing the problem.

I have been running the 3.42's for about a year. No problems related to the PCM in that time. Other issues recently, I have had the steering colum lock replaced, the security system went nuts (lights on & off by themselves, lots of lights and DIC warnings on the panel displays) requiring the BCM to be replaced.

Symptoms with the P 1870 code: trans shifts become VERY harsh once the P 1870 code sets. If I clear the code in the DIC, it feels like the TC lockup is OK when the trans is cold, but there is no lockup hot.

 

I have no idea why this happened, but I would look toward a programming issue. If you have a stock tq, this is a strange one. The torque converter clutch pulse width modulation solenoid valve controls the fluid acting on the converter clutch valve. During the duty cycle, if the correct voltage is not present a ground or a short signal is sent to the PCM setting the DTC P1860 code.

 

This is good, and probably means you're looking for something that's changed recently.

It's quite possible that the PCM was flashed at this time. Did your P1870 problems start around this time?

The harsh shift and no lockup with the code present is normal. If the converter is not locking up with no code when hot it could be a mechanical problem. I do think that's highly unlikely though as these components have been recently replaced. My bet would still be that your custom tuning has been overwritten be a reflash at the dealer somewhere along the line. If the first instance of P1870 problems appeared not too long after a visit to the dealer, say for the BCM problems, it's a pretty safe bet it's programming.

It's worth trying to find a buddy that'll help with the scantool stuff. I really wouldn't expect the dealer to very effective at chasing through this until you verified that it wasn't a programming problem. They can't really solve those and won't even be looking for them.

 

Y'all are GOOD! The problem showed up the day after I picked it up from the local Chevy dealer (the final straw...I will never go back to them). They were told NOT to mess with the PCM without letting me know first. When I came back with the P 1870 code, I asked them if they flashed the PCM they assured me that they flashed the BCM not the PCM.

I am planning another trip to San Antonio to a dealer I trust. It sounds like the PCM will have to be totally wiped out and then go back to MTI to have the programming re-installed over the new (stock) code.

Just curious, the rev-limiter and the shift points are not right (looks like they are back near stock) but the speedo still seems to be accurate, is it possible there was a partial re-flash?

 

Excellent news! Sounds like an easy fix, at least not something mechanical :) The speedometer doesn't require any any recalibration to be correct so there's no reason to suspect any kind of incomplete or partial flash. The vehicle speed sensor (VSS) measures axle rotation rate and already accounts for gearing. This is different from most other cars where the VSS measure rotation rate of the transmission output shaft (in front of the gears) and typically requires adjustment of some type.

I feel lucky... My service writer is a LT1-Edit user and is particularly sympathetic to my "please don't flash me" requests.
:blueangel:

 

Some bad news...and some good news... Today, I went for a ride with the tech in San Antonio and the lock-up did not work and threw the P 1870 code like it was supposed to. While we drove back to the shop, he was playing with the Tech 2 and found he could lock it using that. The transmission guy said it sounded like the tranny was low on fluid, or something was wrong inside, so he wanted to take a look at the fluid. When they dropped the pan, there was a lot of brass particles in the fluid. :(

Now, GM wants to tear down the tranny on Monday to find out what went wrong (in less than 500 miles!). The good news is they are going to fix it, the bad news is that I will experience Corvette withdrawl for about another week until it is ready. Still no word on if it will be a new tranny or a rebuild of this one. I hope they go with a new one, but at this point, I just want my baby back!

When the dealer tech was checking out the PCM, he said it had been recently updated and he couldn't see any "modifications" but knew they had to be there since the 3.42's won't work properly with "stock" codes...(how does MTI hide the code?) I'll still visit MTI to let them check it out when everything else is working.

 

Bummer... :(

As far as determining what code you're running goes, OBD regs require calibration verfication numbers (CVN) to be reported (i.e. computed when requested, it can take a good amount of CPU to do this so you don't do it with the car running) specifically for the purposes of determining if emission related calibrations have been altered. Each specific calibration ID will have at least one unique CVN. Anyway...

Just when you think it's software, those pesky hardware problems creep back in. Good luck getting the tranny fixed. Make sure everything that doesn't get replaced gets flushed out well.

 

I had the same problem with the P1870 code after my gear an TQ were installed. It was due to programming but I have decided to upgrade the trans to an FLP IV due to the torque generated by the turbo. Good luck with this. I would have them beef up the tranny a little bit while they are rebuilding it!!!