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Transmission issue

11K views 31 replies 4 participants last post by  ndnoutlaw87 
#1 ·
I have a 99 Jeep GC laredo with the 4.0 I6 and 42re transmission. the trans works fine when it is first started up, but after it is driven long enough to get warm and it is shut off and restarted the trans over temp and o/d off lights come on and then no overdrive and no fourth gear. then after driving a mile or so the lights shut off and everything works as normal. i've replaced the fluid and filter and also the governor pressure sensor and solenoid. anyone have any ideas?
 
#8 ·
Did you change the governor pressure sensor (which has the temperature sensor in it) for this problem, or was that for something else?
Check the wiring harness for any chaving signs and remove/clean reconnect all connectors in the circuit.
 
#10 · (Edited)
Probably best using a multimeter in ohms range and measuring between both sides of the wire and then wiggle the wiring and look if the resistance changes or maybe even goes to infinite (open wire) . The problem could also be the wiring inside the transmission. Did you check the connector on the transmission already?
Edit: just had a look at my 04 wiring diagram. (Could be different on your 99) you would have to measure between the transmission connector point 8 and the PCM connector C2 point 1. This is the temperature sensor wire. I can confirm tonight when im at home if the 99 wiring is the same.
 
#11 ·
I'll have to use the multimeter on it tomorrow And see what that brings me. I've been looking everywhere for the diagrams on the connectors going into the transmission But I can't find them anywhere. But from what I remember when the pan was down all the wiring looked good.
 
#12 ·
Probably a good point to start wiggling is where you discovered the cuts in the wires, could be a weak point. When i'm at home i will send you the wiring diagram page for the 99.
 
#14 ·
Yesss, we like pictures:D.
Attached the wiring schematic for the 42re. The temperature sensing circuit is just one wire running from the PCM to the transmission. You will need to make one long test wire which will connect to the PCM connector C2 point 1 and the other to the transmission connector point 8. Don´t forget to remove the negative battery connector before attempting to remove any connector. Also never touch the PCM connector pins with you bare hands. Static electricity can build up in our body depending on which type of clothes you use, air humidity and type of shoes, and this charge can easily burn the electronics circuits inside the PCM (or any other electronic device).
 

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#16 ·
It looks that the purple wire isolation is partly gone. If the wire contacts any metal from the casing, it could make a short or a wrong feedback. I will see what the colour of the temperature sensor wire is.
 
#17 ·
Just confirmed that the temperature sensor circuit wire is violet, so seems to be the wire which has the isolation damage. How could this happen like this? Doesn't seem to be chaving.
 
#18 ·
Well that's a long story. Basically from the place I bought it, the jeep had some issues I couldn't see in just a test drive. But how I came into this was they took the thermostat out so it fooled the computer to think it never warmed up. I put the thermostat in to find out they pulled the o/d off And trans over temp bulbs out of the cluster. So I'm assuming they tried to jimmy something to fix it And it didn't work And just left the wire exposed. But a wire on the speed sensor is chaved off And also another connector that goes into the transmission that has 3 ends.
 
#19 ·
That is a place to never buy again, what a bad workmanship. Those wires need to be isolated at least. So as long you have the jeep it has never used 4th gear. Should have used some fuel.
 
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#20 ·
oh it definitely was using it up when i first got it. but the weird thing is though is that after it drives for a little while it will shift into fourth. so you think that if i was to replace that wire going into the connector that maybe it would change the resistance back to normal and hopefully restore everything to normal function?
 
#21 ·
Difficult to tell, since they where fouling around for some reason. Maybe the reason was the temperature sensor and they didn' t want to open up the transmission. So at least it will be a good beginning and maybe even the whole solution.
 
#23 ·
No, the 5V is used for the governor pressure sensor. The schematic doesn´t show the voltage the PCM is putting out to this wire, but the wire spec is mentioned.
The specification is: T54 18 VT. T54 is the number of the circuit. 18 is the wire size (gauge 18) and VT the colour (so violet). But if its only the isolation which is removed, you could also only repair the isolation itself, as long as there is no corrosion on the core wire. Or otherwise splice a new part in between. When you want to change the whole wire, then you have to get new connector pins as well and i have no idea where to get those.
 
#24 ·
Alright guys. Sorry about the long response time. Thank you Florida early raining season. Anyway, I bit the bullet And spliced a new line where to jacket was cut off. Looks good so far. Drove around 15 miles And no ill effects. But when I come to a stop And put the transmission in reverse it feels like its going to stall.
 
#26 ·
So you still get the trans overtemp lt on? And only after being stopped for some time and starting again? Because it seems to be a transmission temperature related problem, it could be internally to the transmission, but also a problem inside the PCM. But you have to be sure that the wiring is ok first, it could have a problem at some others point.
But the fact that the isolation of the wire was removed, is already a sign that something was going on and that they where trying to find the problem.
 
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