tranny vs. engine limp modes and associated codes

[Mark Rinker]

Well it seems that I am encountering a new milestone - my first limp mode on a 2001 lb7.

About 800 troublefree miles after installing an MSD propane system, the truck bucked while towing heavy uphill and then limped. Since that time, the truck will limp whether loaded or unloaded, usually under acceleration or uphill - but only with propane engaged, never under diesel only.

Sure sounds like torque converter or transmission slippage. 110K on truck/tranny.

1) How do I pull the codes?
2) Should I be investigating an upgraded ECM software version from GM before proceeding with any other troubleshooting?
3) If its tranny slippage, can I simply upgrade the torque converter to hold more power, or will I need a complete Suncoast type package?

[SoTxPollock]

Lets see...Pulling hard diesel and propane, lots of heat, tcm detects slippage, defuels engine. The octane rating of propane is way up above gasoline so its not going to self ignite the cold propane, it bucks, loss of power, slippage stops, diesel comes back in power goes back up. Yeah, you might be right about the slippage.

[Mark Rinker]

Things are back to normal - working fine according to the driver. I think it had everything to do with the unusually heavy load that day.

21 mpg (diesel) today - it will be interesting to see the propane numbers when we refill at the end of the week. It all about the total gallons and total fuel cost per mile. So far, its been MORE expensive, but we aren't tuned yet.

[Kennedy]

The 2001 is just a bit goofy in some respects. We've seen it do "phantom" overboost codes etc. Best is to read what DTC's are set (Predator, Tech 2 or EFI Live) and go from there. The best solution IMHO is to reflash (bootleg) to a 2002 OS and get rid of the old programming...

[Mark Rinker]

Thanks for the input, JK. I was waiting for you to weigh in on this topic.

I have a good contact at local GM dealer. Can they do it for me? If its technically possible he will likely do it for me for the asking.

If its technically impossible - can I work with you to accomplish this? Maybe a day on the dyno and some EFI Live lessons are in order.