I've searched, no clear answers yet. I have around 50 miles on my LQ4/80E swap. Was driving home Friday night, got on the interstate - business as usual, nothing out of the ordinary. A few miles up the road, I feel the converter unlock and see the tach jump. Then I feel it lock, then quickly unlock again. I lifted and coasted a bit, got back on the throttle gently, the converter never locked again. Checked fluid level, electrical connections Saturday - everything was in order. Drove it again at various speeds between 50-70 MPH... nothing, converter never locked up. Today I pulled the drain plug, fluid came out like brand new. Doesn't smell burnt, ran it through a paint filter, clean - no residue, etc.

I have no SES light, engine runs great, cruise works, etc. I'm at a loss as automatic transmissions = witchcraft to me.

I'm going to try to get a transmission shop to look at it either Tuesday or Friday. Really bummed, as this transmission has maybe 50K miles on it, never abused.

 

picking up any KR?

 

Is it a stock converter?

 

Some DTC's do not illuminate the SES light on the first event, and some do not illuminate the SES light at all. But some will put the trans into "limp" mode, and max out the line pressures, and prevent converter lockup.

You need to get a scan tool on there to start with. If no DTC's are present, then moniter the trans and converter lockup to see what the PCM is commanding. Then go from there. You need to find your starting point for the diagnosis.

 

im having the same issue let me know what you find

 

Factory torque converter, no KR. Last log - 02s, MAF, etc all looked as they should.

 

If you have software then log TCC status to see if it's commanding lock.

 

Random shot in the dark... but is it something to do with your brake switch? My converter unlocks as soon as i tap my brakes even while still on the gas. When I want to show off from a roll for friends I usually do that just so the converter is already unlocked when I hit it.

I would watch your scan in the primary display while logging what is commanded of the TCC and see if the comp ever tries to lock it.

 

Just an update... super busy with work, etc. Did more searching, reading, etc. Picked up a stop light switch, going to install it tomorrow. Also noticed my left tail light has a bulb out when I moved the truck Tuesday. I'll replace that at the same time to rule it all out. I'll be sure to post my findings. Next step is to spend some more time trying to data log and sort it out. Last resort will be to replace the converter.

 

Easy test. Get a cheapo generic scan tool and do a DTC wipe while driving. Don't read the codes, just wipe them. I betcha the converter locks back up right away for a while.

It's probably a tune issue, mine had the exact same issue (no lockup, phantom code triggered by certain highway conditions) but was easily corrected.