2001 STS OBD code P0741 and P1860
 

P0741 TCC Performance or stuck off, and, P1860 Torque Converter clutch solenoid codes were set.

About a year back, I had run a bit low on transmission fluid. Didn't take much to cause major slippage though. However, after adding some fluid, the transmission operates great. Took the car in for some other service recently and was told the above codes were set.

Since the transmission works perfectly, is is plausible that the codes were set when I went low on fluid and now everything is fine now? I suppose I could have asked the mechanic to reset the codes and then check them again. The check engine light continues to come on, but other codes were present too: P0335, P0385, P0340, C0615 and C0620.

Any thoughts?

Depends on if the codes were current, or history codes.
If you ran it low on fluid a year ago, and haven't had any issues with the trans in that time, then it is not likely the codes are from before. The PCM will clear any codes after a period of time that it does not see the problem any more.
Chances are, tho, that you actually do have a slipping converter lock-up clutch. Far too common a problem on the 4T80E transmission. The P1860 TCC PWM solenoid code is an electrical fault....most likely due to the solenoid being melted. Why would the solenoid be melted, you ask? It's because the seals in the channel plate that seal the fluid pressure to engage the converter clutch are leaking. The PCM will see that the converter clutch is slipping(by comparing engine rpms to trans rpms), and the PCM will ramp up the solenoid to try to control the slippage. Eventually, the solenoid fails due to excessive, constant voltage from the PCM trying to stop the slip. I have seen the solenoids turn into plastic blobs from this problem far too many times.
Replacing the solenoid will NOT fully correct the problem, however. Correcting the real problem requires trans removal to replace the channel plate seals that are actually the problem. :mad:
(you can do a search in the transmission forum here and find several threads on the P0741 code, and the problem with the torque converter clutch.)

Not sure about the other codes without checking to be certain, but the P0335/385 I believe are crank position sensor codes.

The C615/620 sound like codes for the right & left front suspension height sensors.

hth

Thanks for the info. Yeah, I saw some of the other threads on the topic. My primary question was whether the codes would have reset, which you answered. Next question, and I believe I already saw the answer in other threads too, is what if I just let it go. Seems it would just lead to poorer highway gas mileage, but I recall reading that it could damage the tranny. I suppose there is additional stress on the torque converter that is normally relieved when the lock up occurs, right?

Thanks again!
Bob

You will certainly have poorer fuel economy, but that is not the main problem. With no lock up functioning, the trans fluid will overheat, for one, and the slippage of the converter clutch will destroy the clutch....which will shed a lot of material into the rest of the trans...it's a vicious cycle.
If this is an "around town only" vehicle, you could get by for a while by not putting it into "Drive"....just put the shifter into "3". Once the trans goes into overdrive, not having lock-up will increase the heating of the trans fluid immensely. An overdrive trans needs the converter lock-up to help cool the fluid, since once the lock-up applies, there is no "stall" in the converter...it is basically direct drive from the engine to the trans. The stall of the converter is what creates 90% of the heat that an automatic transmission produces.

Thanks again. Let me ask a couple more since it appears that you enjoy answering tranny questions! I think I understand why the fluid would heat immensely if the lock up is not occurring. Basically the fluid is doing all the work to keep the coupling going. When the lock up occurs, the fluid can "relax", right?

If the solenoid is shot, why would the lock up clutch partially engage and slip and wear? Wouldn't it just not engage?

Lastly, wouldn't driving around in 3rd produce the same coupling stresses and thus heat the fluid immensely as well?

Automatic transmissions fascinate and confuse the heck out of me!

Bob

I too have the P1860 and P0741 in my 2001 SLS.

Whats the approximate cost of parts and labor? How difficult is it to do on my own?

I haven't had the issues fixed. Sounded like a fairly expensive proposition to me, and not something for a weekend mechanic. Adam's Apple is very knowledgeable and can give more insight though.

Thanks for the info. Yeah, I saw some of the other threads on the topic.