: Strange PC 0741 code situation - '97 STS



KHE
08-06-10, 08:16 AM
About three years ago, my '97 STS would set the PC 0741 code - I'd clear it and it wouldn't re-set for almost a year so I never paid much attention to it until recently.

It began to set the code every couple of days. There are no other PCM codes stored. The symptoms I've noticed are:

No RPM jump when the brake pedal is depressed while at cruising speed.
Chuggle/fishbite sensation at moderate engine loading - usually on an uphill run. Very intermittent.
Fuel economy is 1-2 MPG lower than usual.
Cruise control has an intermittent issue - it sometimes takes 3 - 10 tries to get the cruise to maintain speed even though the CRUISE ENGAGED message is diaplayed on the DIC. No idea if it is related to the PC 0741 code but who knows???
When the code set the other day, I took the car to the local transmission shop and the tech. took it for a test drive with a scan tool plugged in. The following was noted:

When the PC 0741 code was set, the speed was 58 MPH and the slip RPM was 221. He said the slip RPM needed to be below 200 or the code would set. The shop manual states -10 to +67 RPM.
The tech. could not force the TCC on with the scan tool.
The brake switch status indicated "Closed" even with the brake pedal depressed.
Tech. cleared the codes and still could not force the TCC to engage. Even though the service engine soon light was off, the code was still current when I entered the onboard diagnostics.
The tech. said they rarely, if ever rebuild the 4T-80E trans. as it is such a durable unit. They mostly change TCC solenoids and the ocassional torque converter.

Last night, I tested the TCC switch mounted near the brake pedal and it tested fine. I removed the switch and tested the continuity with an ohm meter. My guess is something is preventing the TCC from engaging and when it eventually does engage, the high slip RPM causes the PC 0741 code to be current and turn on the service engine soon light.

Any ideas what could be inhibiting the TCC from engaging? I do not want to replace the TCC solenoid only to find out my existing one was good. It does sound like the torque converter is on its way out though. Thanks!

mhamilton
08-06-10, 09:40 AM
There's a different code associated with the TCC solenoid failing, it will indicate an electrical fault. The problem you have is with the seals in the torque converter themselves. When the PCM commands lockup, it energizes the TCC solenoid, which then allows pressurized hydraulic fluid (transmission fluid) into the lockup circuit of the TC. The problem you have is the seals themselves are leaking, so the transmission is supplying pressurized fluid, but the leakage prevents the TCC from actually applying.

I actually have the same exact problem on my car currently, just haven't had the repair made yet. When this problem starts out the seals are only partially leaking, so it will apply when cold and when speed is great enough to overcome leakage. Eventually the seals wear out too much, and it won't lockup at all anymore. Time to replace the seals and torque converter, and probably the solenoid just for good measure while you have it out.

Here's all the info you'd ever need on the repair: http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/149834-information-p0741-p1860-1998-a.html

KHE
08-06-10, 04:14 PM
There's a different code associated with the TCC solenoid failing, it will indicate an electrical fault. The problem you have is with the seals in the torque converter themselves. When the PCM commands lockup, it energizes the TCC solenoid, which then allows pressurized hydraulic fluid (transmission fluid) into the lockup circuit of the TC. The problem you have is the seals themselves are leaking, so the transmission is supplying pressurized fluid, but the leakage prevents the TCC from actually applying.

I actually have the same exact problem on my car currently, just haven't had the repair made yet. When this problem starts out the seals are only partially leaking, so it will apply when cold and when speed is great enough to overcome leakage. Eventually the seals wear out too much, and it won't lockup at all anymore. Time to replace the seals and torque converter, and probably the solenoid just for good measure while you have it out.

Here's all the info you'd ever need on the repair: http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/149834-information-p0741-p1860-1998-a.html

Thanks for the information. I was under the impression that when the tech commanded the TCC on, the solenoid wasn't engaging the TCC. That's why I thought it was strange that it didn't set a code for the solenoid.

I'll read through the information in the link - the seals that fail are inside the torque converter correct? I would think if the turbine shaft seal to the trans case was bad, I'd have a transmission fluid leak to the ground.

Looks like I need to find a window when I can drop the trans and fix this. The local trans shop is verbally quoting $1200 but I think I'll tackle it myself. I've never dropped a trans. on a FWD car before but have R&R'd the engine in order to timesert the block. Is the trans R&R job as much of a PITA as the engine removal or is it less difficult? What is the best source for a remanufactured torque converter?

mhamilton
08-06-10, 04:32 PM
If the solenoid was bad the PCM would set a code P1860. The torque converter is getting apply pressure, but the leaking seal is preventing the clutch from engaging. But if you take the transmission out, might as well replace that $20 solenoid as cheap insurance.

There are multiple seals between the trans and torque converter in a TCC setup. The case seal is not the one at fault, so no external leaks. BUT... you definitely do need to replace the torque converter in addition to the seals, because the partial-apply condition will have damaged the viscous clutch.

Sorry I don't know what brand is good for a replacement torque converter. I've done some trans work on older RWD Turbo Hydramatics, but on this one I personally would give it to someone else to make sure it's done right the 1st time, because I don't want to R&R the unit more than once. Basically you do have to drop the cradle just as with an engine swap (though I think I've also heard you can partially drop the cradle and get the trans out the side, might as well drop the whole thing). Hopefully someone else who has done the job can comment on the trans R&R.

Old Skool Soldier
08-08-10, 05:47 PM
I actually just got this code too..same year 97 STS..so torque converter is going? are there any aftermarket replacements? higher stall?

Brandon Meats
02-24-11, 02:30 PM
I know it's been a while since this was posted, but I'm looking into the same repair and plan on doing it myself. I wondered the same thing if a better torque converter was available for when I perform the repair. I did some searching online and came across a company called ARI. They make torque converters for various applications, but the one that caught my eye was the 4t80e with Sonnax conversion. They didn't have much information on the webpage, so I called the company. A tech by the name of Tom called me back about an hour later. I asked him exactly what this torque converter was. He described to me that it's an exact replacement converter, but instead of using the viscous plate, they make it with a Sonnax plate that is an actual lockup plate with metal components. Much heavier duty than the OEM viscous style. He said that it eliminates the P0741 trouble code, functions just as stock and is an upgrade from the stock style. He told me that a lot of people go with the viscous style (which they offer as well) due to the fact it's cheaper and most people are looking to offload the car soon. He also stated that the people who go with their Sonnax converter have noticed no difference in performance from stock (surging, vibrations, or lockup and unlock feeling) of what you'd expect from a luxury car. He said that if you plan on keeping the car and want reliability, go with the Sonnax converter. If you're getting rid of the car, do what you feel. Their viscous setup goes for around $195 and the Sonnax one is around $295. I'll hopefully be doing this within the next week or two and I'll be using the Sonnax converter. And yes, change the solenoid when you have it out whether it's bad or not. It's inexpensive and easy once the trans is out. I had the solenoid fail on me before, and it was a royal pain to change it while in the car. Save trouble, CHANGE THE SOLENOID IF THE TRANNY IS OUT FOR ANY REASON! I also did the filter and seal that's under that cover, along with the pan gasket and pickup screens, as well as the cv axle seals even though they weren't leaking. As long as it's out, do as much as you can. It'll save a lot of headaches later on. Hope this helps anyone else doing the repair. How'd yours turn out?

Here's the link for ARI's Sonnax torque converter. You can look up their other products from the navigation menu.

http://www.ariindustries.net/gm-cadillac-4t80e-wsonnax-conversion-pl480.html