ECM is showing tranny in "Normal D2" mode after warming up... won't shift past 2nd.

[BigDs_C6]

First off, I'd like to say I'm sorry as this is not related to a performance tune that I installed in the vehicle, I'm just using VCM to troubleshoot an issue I'm having and didn't really see a good area to post it... also figured some of you tranny guru's might have some input.


Vehicle is an '01 suburban with a 4L60e. I just recently rebuilt the tranny due to a torrington bearing failure. Tranny ran great after the rebuild for about a week, but now it won't shift past 2nd gear... some of the time. That's where it gets tricky, it only has this issue once it's been running and warmed up. I can let it sit for a few hours after driving it and then start it up and it'll shift normal again... then the failure comes back after driving a few miles.

I've got VCM scanner reporting both "Trans Current Gear" and "Trans Shift Mode" for troubleshooting purposes. When everything operates normal, it shows the shift mode as "Normal Shift". After it's shut down and sat for a few minutes, it shows "Normal D2". If driven in this "D2" mode, it will start out in 2nd gear unless I select D1 on the column (this allows a 1-2 shift or 2-1). It will not shift higher than 2nd. If I get it up to about 35 mph and let off the throttle the rpm's roll back down to idle until I push the throttle again, then the rpm's have to spool back up pretty high before it will hook up and it still will not shift. The odd thing is, if I use the VCM controls in this "D2" mode, it will change the gears as I select them. I've tried putting it in "Performance" mode, but it will only go when it's not acting up.

The only DTC that it's throwing related to the tranny is P1810, but it doesn't always show up when it goes into D2 mode. I've considered changing both shift solenoids and the pressure switch manifold but not sure if it'll help or not. My first suggestion was the wife was just going to have to drive it with the laptop hooked up from now on and shift it using VCM scanner... needless to say that didn't go over too well.

From what I understand, the pressure manifold switch tells the ECM what gear is selected based off line pressures. Figured it could have a bad switch showing closed when it shouldn't be. Also figured it could be a solenoid sticking open allowing pressure to be applied when it shouldn't be.


Any suggestions would be greatly appreciatted!!!






Thx,
D

[almarconi]

When you rebuilt the tranny did you check the solenoids and the pressure switch? Both are relatively cheap and easy to replace. Sometimes if shift solenoid B is not working properly the trans will not shift out of second.

[BigDs_C6]

Thx for the reply...

I did check the solenoids and the temp resistor in the pressure manifold during the rebuild, but not the individual switches. Not sure if it would have shown bad or not with the way it's acting since it's fine when you first start it up.

What I'd really like to know is where the "D2" input is coming from. I'm assuming it's ultimatly the pressure switch module. Like I mentioned before, everything I've read shows that it provides the ECM the data to show what gear is selected. I just thoght this was a little odd though, originally I figured it would have gotten the signal input from the switches in the column.




D

[MikeyZ]

you have a datalog?

[Chris@HPTuners]

http://www.hotrodlane.cc/New%20LS%20...%205.7%20L.htm

i've had this problem before, had to replace the TFP switch.

[BigDs_C6]

http://www.hotrodlane.cc/New%20LS%20...%205.7%20L.htm

i've had this problem before, had to replace the TFP switch.

Thanks for the post Chris, that's exactly what I needed.


Pretty sure this is what I've got going on:



Action Taken When the DTC Sets

• The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.

• The PCM commands D2 line pressure.

• The PCM commands a D4 shift pattern.

• The PCM freezes shift adapts from being updated.

• The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.

• The PCM stores DTC P1810 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.

And this explains why it clears up after sitting for a while:



Conditions for Clearing the MIL/DTC

• The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.

• A scan tool can clear the MIL/DTC.

• The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.

• The PCM cancels the DTC default actions when the fault no longer exists and/or the ignition switch is OFF long enough in order to power down the PCM.

Hopefully the pressure switch module will take care of it, I've got a new one on the way... I'll report back with the results.





D

[BigDs_C6]

FYI for anyone that might happen to find this thread later on and be experiencing the same issue, looks like the pressure switch module solved the problem.

I picked up a new p/s module and 2 new shift solenoids (figured might as well swap them out too if I was going back in) off the big auction site for $50... not too bad for Delco parts. Installed them today and it's been running great, hopefully that'll be it for this one and I can start to concentrate on tuning my C6. I've got everything I need including a wideband, just gotta get going.



Thanks to all that helped out...



D

[Chris@HPTuners]

glad you're up and running again