GM Connect & Cruise Intermitten issue

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H

hatleye

10 Year
Joined
Oct 5, 2014
Threads
20
Messages
165
Location
Charlotte, NC
I purchased an FJ62 a while back and all has been well, just working through little projects and learning what makes an FJ62 tick [well, what is left of the original and learning what has been changed], until i hit something over my head.

Little background....the engine and transmission in mine has been swapped to an LS3/Auto connect and cruise package. It has always been a little weird when you let off of the accelerator approaching an intersection, but the light has just changed and traffic clears for you to accelerate again, the FJ tends to down shift if you don't give the transmission plenty of time to "decide" on what to do. Made me feel like something was fishy with the torque convertor.....but i haven't decided on the plan of action to troubleshoot it.

The issue.....
I was driving along at 55 or so and suddenly the FJ downshifted to what i think is second gear and refused to shift up. I pulled over, shut it off the engine and looked around to make sure nothing mechanical gave way and found nothing wrong. Apparently this power cycle "reset" the controller.

I hopped back in to "limp" home, and it shifted perfectly. I tested it a couple times by accelerating hard and everything functioned perfect.


I am 100% sure i don't trust this situation, but I am not sure how to troubleshoot it. I am suspecting that i start by looking at the grounding for the system as i heard these controllers are very sensitive to that.


If anyone has an idea to check.....i would appreciate the help.
 
fluid level in the transmission? Any codes set in the ECM, any history of recent work that impacts transmission, did it shift ok or is this part of the gremlins of a new engine swap...
 
My observation:
-fluid level seemed ok, but this group would know more. I checked this level at semi-warm [had just started moving the temp reading] with engine idling, in neutral; it was about halfway in the run range on the dipstick.
-I will check ECM with scan tool and report results.


It just blew me away that an engine restart cycle would change this condition. It shifted as usual before the incident and after the engine restart [i had driven ~100 mile trip yesterday].
 
Engine restart tends to reset limp mode.
 
And the mystery gets more interesting, no codes. Or at least no code reported by my little cheap reader.

Not sure if it is related, or all in my mind...but this engine seems to run a little cold natured. Starts great, but runs like it is running a high performance cam, until it gets warm, just an observation...probably nothing to do with this issue.
 
Just to be clear, you're talking about the controller being swapped, and not the 3F-E/A442F for an LS3/? engine/transmission, right?
 
the whole enchilada. Mine has the LS3 swap with auto transmission. I need to get exact part numbers....but it was all from crate components.
 
I wish I could help, but my knowledge of Corvette engines/transmissions is really slim. I can offer a wrench or two, if that'll help. Let me know.
 
thanks....glad to see a fellow Charlottean on the boards. Have to get the FJ's out and compare notes soon.
 
Lot of power for an FJ62!
The main grounds are generally on the back of the drivers side cylinder head for the ECU. Make sure your trans harness is fully plugged in (Above pan on the Pass side) Also check your plug ins for the pedal on drive by wire, and the sensors around the intake for throttle position and air flow. Trans shifting is related to throttle position, as well as load. I assume you have a 4L60 or 4L65 trans. If you have the 6 speed auto 6L80, they are knows to do some gear searching on swaps. Takes a tuner a little time to get them dialed in for the weight load vs a corvette
 
thanks for the advice, i was expecting a loose connection or grounding issue....as it just runs too well otherwise. It is a lot of fun to drive...
 
Shes Mad said:
Lot of power for an FJ62!
The main grounds are generally on the back of the drivers side cylinder head for the ECU. Make sure your trans harness is fully plugged in (Above pan on the Pass side) Also check your plug ins for the pedal on drive by wire, and the sensors around the intake for throttle position and air flow. Trans shifting is related to throttle position, as well as load. I assume you have a 4L60 or 4L65 trans. If you have the 6 speed auto 6L80, they are knows to do some gear searching on swaps. Takes a tuner a little time to get them dialed in for the weight load vs a corvette
Click to expand...
You have to remember he lives in the NASCAR zipcode; we all drive more car than necessary. It's sort of a social imperative.
 
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