E38/T42 4l65E (no ISS) TCC fix???

[vette5797]

I have a 62 Corvette/LS3/4l65E E38 OS 12617631 /T42 OS 24239927

After a few short drives my TCC stops working and gives code P0741 "TCC system stuck off". Clearing the DTCs allows normal operation again for a few short drives until the same occurs again. Searching all the forums, I've learned that apparently the E38 needs to see an ISS signal. Another forum suggested that although their system didn't have a cure that EFI Live (which I have) did have a fix for this. I found D7026 Input speed sensor, and changed it from yes to no, hoping that this was the fix, but it didn't help. Can somebody tell me what the fix is? All components are new GM over the counter, so I'm confident that it's a tune or install issue. Any help would be greately appreciated. Thanks, Gary

[joecar]

Does your 4L65E have an ISS sensor...?

[vette5797]

Hi Joecar. Thanks for responding so quickly. No it doesn't have an ISS. It's a GMPP purchased two years ago when the project began. Scanning while driving shows TISS as zero, and TCCslip appears to be engine RPM. Gary

[slow67]

What about also turning off P0716 and P0717?

[vette5797]

The DTC codes p0716 and p0717 are still shown as reported codes, but they are not showing up. Only P0741 shows up.
I've also read a number of posts with related issues saying to set C5601 "misfire detection max temp" to 1degree. Neither my ECM nor TCM show that parameter. C0611 seems to be the closest thing I could find. Is that the same parameter for this system? Should I try setting it to 1 degree??

[Taz]

Hello vette5797,

Can you post your original (never modified) ECM & TCM tunes ? Don’t mind taking a look to see what (if anything) could be done.

From memory, when the ECM runs the trans slip diagnostic, about a 250 RPM difference between the ISS and the VSS is allowed (that number may be different for various applications - just intended as an example).

I don’t recall if a DTC is set if the values from ISS and VSS are the SAME. If not, perhaps slicing the ISS into the VSS would be a “hardware” fix for your VSS only transmission.

Just a thought …..


Regards,
Taz

[slow67]

If not, perhaps slicing the ISS into the VSS would be a “hardware” fix for your VSS only transmission.]
Problem there is, the ISS on a 4L70 (I'd assume 4T70 would be the same) is the ISS wheel is 17 tooth, and VSS wheel is 40 tooth.

[Taz]

Good point ... didn't know that ... good news is that 17 tooth reluctor is the same as the manual transmission (I believe). In the TCM .. H0103 ... in the speed calculator ... can set the VSS reluctor to either 17 or 40.

If there does not end up being a "tuning" fix ... then replacing the 40 tooth reluctor with a 17 tooth ... would allow the ISS and VSS to "share" a signal.

Right now we're just "bench racing" as they say ... once the tunes are posted, a "work around" may present itself.


Regards,
Taz

[Taz]

Hello vette5797,

Sorry … focused on your transmission issue and didn’t answer your misfire question.

If the engine is a GMPP crate engine, with no modifications, I would recommend leaving the misfire diagnostic active - often helps sort out issues (i.e. defective coil, poor connection to an injector, etc.).

Sometimes when an enthusiast installs a larger cam, or makes other modifications, rather than working out the “best” tune, or appropriate diagnostic parameters for the particular application, they simply turn things “off”.

While this approach is quick and easy, it fails to fully utilize the PCM’s (or ECM, TCM) ability to monitor the engine / transmission. There are times when this approach may be necessary, or partially necessary - but is properly used after tuning solutions have been exhausted.


Regards,
Taz

[vette5797]

Thanks Taz, slow for the help. Yesterday I went ahead and changed c0611 to 1degree, reflashed and went for a drive with the v2 scanning. Misfires stayed at 0 but after about ten minutes the TCC quit again. So I think that rules out misfires as the cause. I did find out though that by just shutting off the car and starting back up that the TCC will work again for a short while, even though the p0741 is current. Is there anyplace I can find the list of parameters that set P0741 on a 2008 era 4l65E. I've googled my butt off but can't find much specific to the 4l65e. Also, I don't know how this trans compares to the aforementioned 4l70 or 4t70 transmissions.
Regarding the tunes, this project started over two years ago right when the LS3 became available over the counter from GM. The GMPP complete LS3 package still wasn't available yet so I ended up with the long block version and had to purchase separately the intake,rails,injectors,coils etc. The LS3 intake wasn't available, so the Holden version with diffrent MAP sensor was used. I tell you this so you'll understand why the MAP is scaled and other mods. My original tuner started with the 2008 Silverado ECM and TCM tunes, apparently one of the only ones available at the time that used E38 and T42. Later, I think he swapped in and modified the Corvette LS3 tune for the ECM. These (hopefully I've uploaded them properly) are the tunes in the car today. Again, any help is greatly appreciated. Gary
Taz, also agree regarding the misfire detection and plan on changing that back on next flash since it didn't help cure the problem anyway.

[gmh308]

Thanks Taz, slow for the help. Yesterday I went ahead and changed c0611 to 1degree, reflashed and went for a drive with the v2 scanning. Misfires stayed at 0 but after about ten minutes the TCC quit again. So I think that rules out misfires as the cause. I did find out though that by just shutting off the car and starting back up that the TCC will work again for a short while, even though the p0741 is current. Is there anyplace I can find the list of parameters that set P0741 on a 2008 era 4l65E. I've googled my butt off but can't find much specific to the 4l65e. Also, I don't know how this trans compares to the aforementioned 4l70 or 4t70 transmissions.
Regarding the tunes, this project started over two years ago right when the LS3 became available over the counter from GM. The GMPP complete LS3 package still wasn't available yet so I ended up with the long block version and had to purchase separately the intake,rails,injectors,coils etc. The LS3 intake wasn't available, so the Holden version with diffrent MAP sensor was used. I tell you this so you'll understand why the MAP is scaled and other mods. My original tuner started with the 2008 Silverado ECM and TCM tunes, apparently one of the only ones available at the time that used E38 and T42. Later, I think he swapped in and modified the Corvette LS3 tune for the ECM. These (hopefully I've uploaded them properly) are the tunes in the car today. Again, any help is greatly appreciated. Gary
Taz, also agree regarding the misfire detection and plan on changing that back on next flash since it didn't help cure the problem anyway.

This post jogged my memory...the OS & cal you are using from the Vette is an A6 friendly cal. If you want to use that OS, then to check whether this issue is being caused by the ECM's preference to see an A6 you could drop a Yukon 5.3 calibration in. Otherwise try a process of elimination and turn the TCM fault behaviour settings off.

[Taz]

Hello Gary,

Thanks for posting the tune files. Both the ECM and TCM tunes are from a 2008 Yukon 4 x 2 with a 5.3L (LY5) engine and a 4L60E / 4L65E / 4L70E type transmission. Given Ian’s (gmh308) comments, this tune should (hopefully) lend itself to your application.

I did not make any changes to the engine tune (ECM). In the TCM (trans) tune I changed the values in D7014 and D7015 - which may not make any difference.

Everything else generally looks OK. Trying to think “outside of the box” - do you have a brake switch wired into the harness ?

My experience is primarily Gen III swaps - this is a Gen IV, so it’s a little outside of my area of expertise. The Gen III PCM needs to see voltage from the brake switch when the brakes are NOT applied, and conversely no voltage when the brakes are applied - to appropriately manipulate TCC function.

Something to check … not sure if this applies to a Gen IV. I renamed the file to avoid confusion – posted below.


Regards,
Taz

9194

[gmh308]

Cool. If the Yukon ECM file sees the throttle going into limp mode (which it may depending on the base calibration in the ECM), PM me, may be able to get my hands on one that wont. :)

[vette5797]

Taz, Ian , thanks again for your help on this issue.

Taz- yes I do have a brake switch and I believe it's hooked up as you said. I also have a similar gen III car and I believe we wired the brake switch the same as that car. I checked it the other day. It has a purple wire in and out. Closed when brake off, open when brake on.

I'm real new to all this stuff, but did a short log the other day. This is after the TCC had quit and p0741 was current. I pulled over and shut the car off and restarted it, then started the log. Two things on the log have my concern. The first is that I don't see any changes to the brake pedal parameters even though I know I pressed the brake a few times in this short run. The second thing, which I think is the smoking gun, is the TCCE test parameters. The TCCEP "short to power test" goes from Failed to Unknown to Failed a few times during the run ( note frames 815, 1415-1419, 1609-1615, then the TCC quits immediately after it goes Failed again (2055), noted by the PWM going to 0 and then the TCC remains off till car is restarted. I don't think these test Failures are related to the brake since I was actually accellerating slightly when I felt the TCC kick off.

Today, I'm going to disconnect the brake switch and see if that affects anything. Then I may try doing some more logs.

Ian- which behavior settings would you change? Almost all of them appear to be off now.

Anybody know a likely culprit for a short to power???

Thanks again guys, I greatly appreciate you sticking with me. Gary

[vette5797]

Guys, pulled the two purple wires from the brake switch, cleared DTC's, and went for a drive. Thought the car would die when I put it in gear or come to a stop, but it appeared to drive and stop no different than with the brake swich connected up. Scanning through the TCCE parameters I noticed that the TCCEP parameter was now going between indeterm and passed. Never showed passed before. Yay, thought I found the cure, then a couple miles later down the road the TCC quit again. Just scanning, not logging, but the TCCEP was not showing failed as it did before. Brought back to the garage. Checked DTC's and P0741 present as expected. Read out the switch and it was like I thought, normally closed, open when brake pedal pushed. Checked the two purples to ground, no cont. Checked voltage with ign off- zero on both. Turned ignition on , one purple reads battery voltage 12.6 , other read 9.6 volts. I'm going to have to get behind some panels to trace the wires. Obviously one side is Ign pwr. The other I believe is the brake switch leads of the ECM (pin 9) and the TCM (pin ?) connected together. I'll go verify this, but does anybody know for sure that this would be the correct connections? Also, does 9.6 volts make sense?? My FAST Perfect Circuit engine harness data shows pin 9 to go to the brake switch, but doesn't say what should be on the other side of the switch. I never got a data sheet for the FAST trans harness (I'll call them and see if the have one).
I would think that this has to be the problem area. Any suggestions or inputs would be greatly appreciated. Thanks again, Gary

[Taz]

Hello Gary,

Regarding the TCC brake switch …

As stated previously, my experience is primarily Gen III swaps - so the following comments are Gen III based - you will have to confirm the appropriate Gen IV circuits / wiring diagrams.

The Gen III PCM needs to see voltage from the brake switch when the brakes are NOT applied and conversely no voltage when the brakes are applied - to appropriately manipulate TCC function.

A 12 volt 10 amp power source from the vehicle is routed to one side of a “normally closed” switch on the brake pedal. The other side of this switch is wired to the PCM (often C1 pin 33 - purple wire). The PCM grounds this circuit.

If this circuit is not connected (or malfunctioning) DTC P0719 is set (no MIL) and the TCC will remain “off” (not locked).

If this circuit is connected to a constant power source (no brake switch to intermittently interrupt the power) DTC P0724 is set (no MIL) and the TCC will remain “off” (not locked).

If the PCM detects high TCC slip when the TCC is commanded “on” (locked) then DTC P0741 is set - in other words the TCC is slipping (not locked) when it is supposed to be locked.

You mentioned that you checked both wires on either side of your brake switch, and one had 12.6 volts and the other had 9.6 volts. If the Gen IV is similar to the Gen III in this regard, then one wire should have 12 volts (fuse panel side) and the other should have zero volts (ground - PCM side).

Guessing that your TCC is not locking - probably from not receiving the appropriate 12 volt input.


Regards,
Taz

[1badss]

I know this an old post/thread ,but I am having the same exact trouble with my 2007 Trailblazer SS started intermittently just maybe 1 time every 3 months and now after a converter swap it is just like Gary's situation locks fine then after a short period of driving stops locking and throws code PO741, I also have got code P0700 one time with PO741 it and the very first time this happened it blew a fuse and ever since it just acts exactly like Gary's. Did this ever get fixed for Gary ?

[Taz]

For now, post your ECM & TCM tunes. If these check out, would then need a log of what is happening.


Regards,
Taz

[vette5797]

Guys, It's been a long time since I've been to this forum or even touched my EFI Live and my memory is very poor. Back then someone suggested to change P0741 to not reported. The theory was that if it's set to reporting it does a test. If it fails the test, then it locks the TCC out. When set to not reported then it doesn't do the test. I did this and have not had any problem with the TCC since. Of course, now if there is a problem I won't have a MIL or code set, but I would feel the problem (TCC unlocking) anyway. Since everything is brand new from GM I feel confident that everything is mechanically sound, and that the solution to this problem is just a glitch that had to be done when mating parts that weren't designed to be together. BadSS, hope this helps you. Taz, thanks again for all your help years ago. Gary