Transmission will not engage

[hydromax]

After vehicle was parked for more that 5 days in garage transmission would not engage, first event only malfunctioned in reverse, shift indicator flashing in reverse position. The second event occured after vehicle was parked, this time not only did reverse but also forward gear. Shift indicator flashed in both "R" and "D". On both occations condition corrected itself by shutting engine down and restarting. SES lamp remained on after each event for approximately 40 miles.
Stopped by dealer and they found multiable codes:
PO700, PO841, PO870, PO871 and PO875. They reported that they found updates and repropgramed.
My question is this the real fix or should I expect this to reoccur.

2002 Duramax/Allison
21,000 miles

This is first trip to dealer for other than scheduled maintenance.

[DonG]

hydromax,

This problem was discussed some time ago and BigAl provided his excellent comments on how to avoid this if you leave your truck set for a number of days. His comments are below. You may be able to find the thread that discussed this a while ago.

BigAl:
"Having re-read this entire post, I believe I know what happened. I'm guessing you jumped in, started her up, and threw her in gear (like normal, right?). Some of the trannys have a tendency to "drain-down" after sitting idle for extended periods (6-days would qualify). When this happens, and you go out and start it up, a slug of air goes through the system, causing some of the pressure switches to "drop out" (i.e. they don't see pressure when they are expecting to). No problem if you are still in Park, but if you have the shift lever in gear (reverse or drive, this causes the tranny to suspect something is wrong (He wants to go, but I don't see no steenking pressure!! ). In reality, there isn't anything wrong........but in the meantime the tranny will defend itself by restricting your access to gears (limp home mode).

By recycling the system after the drain-down was gone, you got out of limp home, but the tranny had already thrown a code (SES Light!) and the Dealer technician gets pointed toward the Pressure Switch Manifold (P/N 24222079). I'm betting nothing was wrong with the switch.......just doing it's job........senses no pressure (accurately, when the air went through).

Try this the next time you let it sit for a few days..........start the truck and let it warm up in Park for a couple of minutes (don't touch that shift lever). The air, if it is present, is going to chug through the system during this time and get purged. Shut the truck off for 10 - 20 seconds, and then restart it. Throw her in gear, and I'm guessin' all will be well. P.S. This drain-back situation can be made worse if you park on an incline, nose up! (like my driveway!)"


I hope BigAl's comments help. Don

[hydromax]

On both occasions vehicle was parked on level garage floor, engine was run to allow time for oil pressure to get to normal pressure plus battery voltage had recovered to full 14 volts prio to shifting from P position. I am pretty patient. I estimate eingine was up to normal for 1 minute or more before shifting from P. I will pay close attention next time around.

Thanks

[DonG]

hydromax,

I believe you on running for a minute or so, but the key input is shutting it back OFF and restarting the truck BEFORE you shift. Shutting it off allows the tranny to "forget" that it started with no pressure.

[hapaschold]

thats what happened to me also, stopped to use cell phone, for 5 minutes or so,left running, then put in D and was just flashing, tried again, no go, restarted truck, no problem since.

i checked for codes, but none recorded. will have to talk to dealer next trip in.

[SteveO]

hapaschold,

Your problem does not sound the same as topic.. Your's is more like an NSBU, nsbu adjustment/wiring to NSBU ...

Hydormax''s situation the truck will need to be parked for about 5 days for this to happen and it will show up when he first starts it.. After the intial startup all is good..

[ 12-21-2002: Message edited by: SteveO ]</p>