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Trans won't lock up when warmed up


trox
07-24-2014, 02:53 PM
I have a S10, 2000, 2.2 liter with 4L60E automatic transmission. The trans was rebuilt just before I got the truck and I verified this at the shop that did it. It's got about 45k on the trans since this rebuild. It started jumping in and out of TC lockup intermittently not long after I started driving it. No codes set and no light at all. I took it to the same trans shop that did the rebuild and drove it with a scanner and it wouldn't malfunction for them and they saw no stored codes. Then it went for several months and only slipped in and out once in a while so I lived with it. It started getting bad again so I took it back in and it acted normal again for them. I said if I drive it to work and it does it on the way I’ll come by so they agreed. The next day it started going in and out after about ten minutes down the road so I went straight to the shop. By the time I got there it wouldn’t go to lock up at all. He drove it with me and the scanner showed the TC was not being told to go to lock up. He said the trans wasn’t at fault. He could see the temp was steady and OK, the TPS (throttle position sensor) was a little low but steady and not the probable cause and VSS (speed sensor) was steady and looked good. He said he could only guess the computer was bad. I’ve since replaced the computer, TPS, and the VSS with no luck. I’ve ohmed out the wires and connectors from sensor to PCM connector as far as I can reach for each of these parts and find no broken or shorted wires. It seems to get worse when it warms up to the point it won’t lock up at all now. The temp gauge is rock steady so I don’t think it’s bad or the wires. If I drop it down to 3 it seems to work fine up to what seems like 4th gear. I’ve tapped the brake pedal and pulled up on it with no change. I’m at a loss now since the trans shop says the trans is good. Does anyone have any helpful advice?

maxwedge
07-24-2014, 06:28 PM
If the pcm fails to command tcc, then one of the critical sensor inputs is skewed. Get the diagnostic trouble tree for no tcc function.

trox
07-25-2014, 09:38 PM
I found a GM diagnostic page that has what should be most checks. I'm going to put it on jack stands and run it up. I was wondering if I pull the plugs from the brake switches would that take away any input from getting to the PCM if they are causing my issue?

trox
07-26-2014, 01:31 PM
OK...I disconnected the brake light switch and drove it to see what happens. It was the first drive of the day so it was cold (85 degrees F). It went great through the 4 gears and into lockup. Seemed to be ok until I stopped and ran it up through the gears again and it started going in and out of lockup until it wouldn't even try anymore. It also seemed to bounce between 3rd and 4th?? Very hard to see 3rd to 4th so not sure what was happening there. Once it stops using lockup I can change the shifter from D to 3 and see no difference in RPM. I put the brake switch connector back on and thought I would OHM out the MAP sensor connector to the PCM and clean the MAP sensor while I was at it. Map sensor connector and wires I could get to OHM'd good so I put it all back together and put the back wheels on jack stands. Started it after the hour of messing with it and ran it up through the gears and into lockup looking good. Stopped wheels and ran up again and it started bouncing in and out of lockup and eventually stayed in 4th. With the wheels off the ground it is very hard to see 3rd to 4th gears but again it got to the point where changing from D to 3 made no difference in speed or RPM. The site I thought might help me with this isn't what I was looking for. I need to find a site for 2000 4L60E input sensor testing. It really seems to be temp related but the water temp gauge is rock steady. Is there another output for water temp to the computer? Could it be trans temp related? Running out things to do here. *******Does anyone know of a good diangostic trouble tree for no tcc function????????

maxwedge
07-26-2014, 03:40 PM
Tough to diagnose this without the use of a bi-directional scanner, you can manually engage all gears and lock up without any sensor blocking it, then if ok you can go back and try the conventional way allowing anything that might prevent tcc to be seen on the scanner. Google no tcc 4l60e.

trox
08-13-2014, 02:11 PM
OK, I had it scanned by another trans shop that confirmed what the first shop said. The trans is doing what it's told to do. Since I've replaced the PCM, TPS, VSS, TFP switch maniflod and tested the MAP switch, this guy says it really only leaves the wiring. What I need is diagram with pin numbers/letters of the PCM connectors C1 and C2 to the trans connector so I can ring them out. Currently I have the trans going to 3rd gear and then lockup but not 4th gear with lockup. Anybody have a diagram and a good place to start with my meter?

j cAT
08-13-2014, 06:05 PM
OK, I had it scanned by another trans shop that confirmed what the first shop said. The trans is doing what it's told to do. Since I've replaced the PCM, TPS, VSS, TFP switch maniflod and tested the MAP switch, this guy says it really only leaves the wiring. What I need is diagram with pin numbers/letters of the PCM connectors C1 and C2 to the trans connector so I can ring them out. Currently I have the trans going to 3rd gear and then lockup but not 4th gear with lockup. Anybody have a diagram and a good place to start with my meter?

the transmission most likely needs new A/B solenoids at the least. when doing this inspect these valve bodies for wear.

ask the tranny shop if they replaced these valve bodies. what tranny fluid did they use dexronIII or the DEXRON VI which has been the only fluid to use in these since 2006.. dexron III is a defective no longer GM approved fluid for transmissions. when was the fluid replaced 50K miles ago...?

trox
09-03-2014, 04:47 PM
I found my problem. Well I paid an electrical guy to find it. I had ohmed out the wire harness from the big connector on the trans to the PCM specifically looking for an issue related to code P1814. The blue wire was hanging by 1 strand which gave me continuity but it wasn't enough to carry the load of the 3-4 solenoid. The electrical guy pulled on all the wires at this plug and it pulled right out showing all nut one strand of about 8 broken off. I bought a new connector with 20 inches of wire to splice onto my old harness and the trans has never shifted better. I hope this helps others to realize that wires will ring continuity on 1 strand but won't carry the load.

maxwedge
09-03-2014, 09:30 PM
Good info!

j cAT
09-04-2014, 07:48 AM
I found my problem. Well I paid an electrical guy to find it. I had ohmed out the wire harness from the big connector on the trans to the PCM specifically looking for an issue related to code P1814. The blue wire was hanging by 1 strand which gave me continuity but it wasn't enough to carry the load of the 3-4 solenoid. The electrical guy pulled on all the wires at this plug and it pulled right out showing all nut one strand of about 8 broken off. I bought a new connector with 20 inches of wire to splice onto my old harness and the trans has never shifted better. I hope this helps others to realize that wires will ring continuity on 1 strand but won't carry the load.

the transmission connector and the wires/connector to it are fragile. the tech was not too careful when this was last worked.
thanks for the feedback.

this connector to remove is squeezed then pulled straight out ..also if with fluid in this connector and or debris it will do the same thing with the issue like you had... a wire that was causing a voltage drop due to the wire damage shows that the repair shop was not doing this job properly.
good luck..

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