LS3/4L80E Issues - P0751
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LS3/4L80E Issues - P0751 Hello All, I have a Land Rover Defender in the shop that is really stumping me. Has a new crate LS3 and a new 4l80e installed by another shop, whole package ordered from GM Performance Parts, including the ECU and Supermatic TCU. I believe this is the "Connect and Cruise" system. I have only previously had experience with standard factory ECU's and Holley stuff, so this Connect and Cruise is new for me.
The truck drives well, shifts well, but will go into Limp Mode and get stuck in second gear pretty regularly. I replaced fluid, filter, and shift solenoid A just to be sure, but as these are new units, it all looked good as expected. Behavior remained. The Supermatic software describes P0751 as follows:
P0751 - High Ratio Error
No DTC 21,22,24,38,72,74 Sets when not in P,R,N, RPM is greater than 300rpm, TPS is greater than 25%, VSS is greater than 7mph, Transmission Ratio matches 1st or 2nd gear when 3rd or 4th gear is commanded, for 6 seconds.
On a recent test drive while datalogging, I noticed both times I replicated it was up a steady hill while holding second gear. I thought nothing of it, as I would expect the trans to hold that gear given my throttle position. It seems it just got mad it was in that gear for too long?
At this point I really feel this is a tuning/software issue and not a mechanical issue. I attached the calibration and datalog in a .zip
Any and all help and advice is appreciated,
Thanks
The truck drives well, shifts well, but will go into Limp Mode and get stuck in second gear pretty regularly. I replaced fluid, filter, and shift solenoid A just to be sure, but as these are new units, it all looked good as expected. Behavior remained. The Supermatic software describes P0751 as follows:
P0751 - High Ratio Error
No DTC 21,22,24,38,72,74 Sets when not in P,R,N, RPM is greater than 300rpm, TPS is greater than 25%, VSS is greater than 7mph, Transmission Ratio matches 1st or 2nd gear when 3rd or 4th gear is commanded, for 6 seconds.
On a recent test drive while datalogging, I noticed both times I replicated it was up a steady hill while holding second gear. I thought nothing of it, as I would expect the trans to hold that gear given my throttle position. It seems it just got mad it was in that gear for too long?
At this point I really feel this is a tuning/software issue and not a mechanical issue. I attached the calibration and datalog in a .zip
Any and all help and advice is appreciated,
Thanks
