4l60 no 4th gear

[Jaso74]

Hey all .

Auto was working fine, pretty standard higher km's sluggy 4l60e .
Chucked a corvette servo in because well , 60 bucks why not .
Pretty easy job , took nothing off just worked in the space I had between body, trans, and exhaust . 1.5 hrs later all good , refilled lost atf , roadtested at 7.30 at night runnning great and shift time between 1st and 2nd much better but not harsh at all.
Forward to yesterday arvo and went for a drive , at around the 35 minute mark wouldn't upshift to 4th anymore , no bangs no nothing just wouldn't upshift.
Got home and looked at log and can see in desired gear it wasn't requesting 4th only 3rd.
Did some reading and can think of three real common issues, One would be the 2/4 servo pin is too short( I didn't check it at all just reused original), 2nd would be the manifold switch plate and third is solenoid/s.

Obviously could be many other things but got to start some where.
Feels like servo rod is an obvious one but the not seeing requested 4th gear in the log seems to make that not likely .

Any tips anyone , had same issue or similar ?

[immortality]

Shift points are governed by road speed and TPS. Make sure both of those are reading correctly first.

[Jaso74]

Pretty sure both were ok but I will recheck the log tonight after work. Will also look at tps operation in tp5 with key on .

[Jaso74]

Ok so , Looked at drive log data from yesterday. All seems mostly good as far as tps , speed sensor , etc.
There was a discrepancy though between the tps engine data and trans tps at the same point , namely full throttle of one instance anyway. The eng data says 4.86 volts and 99.61 throttle % but trans says 4.21 volts and 100% . I believe the trans stopped shifting correctly after that point , no dtc's were logged so nothing went open circuit or short to ground . Also when I have all four tps data pids on the data monitor, you can see a blip in the trans voltage and % that is not there in engine voltage and %.

Surely the four different data streams for engine tps voltage, engine throttle % , trans tps voltage and trans tps% all are read from same point in ecu or not ???
Not really sure what to make of this .

Looking at the tps data live with key on in tp5 all seems ok , moves smoothly with no strange jumping or pausing in travel of throttle/tps.

It gets better though, I took ute for a drive not long ago for about 15 minutes and didn't miss a beat !
I took a log but haven't looked at it yet .
Seems might be a heat induced issue, this drive was my longest yet in one stint too, around 45 mins total drive.

[immortality]

Intermittent faults are a bitch.

Next time out try going 100% TPS and see if the fault re-occurs.

[Jaso74]

Rito sounds good , will do .

[Chuff]

This is from the service manual as to what may be the causes of no 4th gear.

4L60 $th Gear ProblemsA.png (111.63 KiB) Viewed 303 times

4L60 $th Gear ProblemsB.png (34.45 KiB) Viewed 303 times

[Jaso74]

Thanks for that Chuff. Luckily in a way , most of the hydraulic items are much less likely now due to the currently not active fault ! Electrically much more so likely .

I looked over the log data again last night and I have a pretty strong feeling that there is a wiring/connection issue possibly at the trans connector or the ecu at this stage. Mostly due to the erroneous data from the engine tps data vs the trans tps data.
This would also fit in perhaps with a heavy foot throttle moment possibly influencing a wire/connection issue.
Anyway I'm going to look at that stuff next , I have a new tps sitting here to throw on at some stage, for 35 bucks why not , I also have a few items ordered for the internal of the trans including a manifold switch plate and the pair of shift solenoids and a boost valve repair kit in the .500 size which can only help a tired trans giving a slight line pressure increase over all.

But first thing I will look at is wiring and go from there . I'd love to find a repeatable fault item, repair that to be sure I have fixed something at least .

[Jaso74]

Ok guys just for anyone else having same or similar issue, I replaced the tps sensor on weekend and appears problem solved .
I didn't have any dtc's originally when fault occurred but started to have check engine light illuminate last drive previous to tps replacement .
Fault code was 22 tps . It was a bit weird but could pretty much make it happen by using wot under load on one drive cycle repetitively .
Any way seems fixed currently , nothing else was touched other than the connectors on throttle body, didn't clean or bend pins or anything like that , tps spacer piece was present and refitted with new tps, tps voltage at closed throttle with old one was .63 volts and with new one .40 volts .
Thanks for help once again guys !

[immortality]

Happy days