Overdrive misbehaviour ('94 GC Laredo 5.2V8)

[HSawabe]

I have a very strange problem with mi '94 GC Laredo.

It hapens when driving for a while that the overdrive starts switching on and off repeatedly, making the transmission to shift between 4th and 3th as the OD switches.

One weird thing that I do trying to force the Trans to not to Shift and stay in 3th is to turn on the Cruise Control (???), so by any cause the OD sticks off.

Then, if I switch off and on again the Cruise Control, the OD turns off... and if i do that again (CC Off and then On), the OD turns on again.. and so on.

Eventually, after driving for a while, the OD does not turn on nor off when pushing the OD button, but it does when doing the CC OFF&ON (???).

Also, I've found that, sometimes the OD is ON when starting the car and sometimes is OFF.

I had the Trans Repaired ($$$$) and still have the problem, then I returned with to the shop and they told me they changed some sensors (without charge) and the problem still remains.
Actually, the shop is willing to correct the problem, because they sent my car to a specialyzed electric shop to check all the connections and charged me nothing (because I took my car there to correct the problem and they do the trans repair without success with the failure).
By now, I'm just about to take it again to the shop, but I'm a little bit desperate because it seems impossible to find out the root of the problem.

Please HELP !!!!

Regards,

Hiroshi Sawabe

[HSawabe]

I forgot, might be related with this, because also, if driving to much in the traffic, I get also a "Check Engine" signal at the same moment the OD switch stops responding.

[dksob81]

I am not sure about this, b/c you say the OD goes ON and OFF, but you may want to have the tranny cooler lines flushed out, they ay be clogged causing the tranny to overheat.

when the tranny overheats it shuts OD off to help cool the tranny. I have never seen/heard of the OD going ON/OFF like you described.

[HSawabe]

Yes, as you quoted, the O/D indicator start blinking ON and OFF and actually, the tranny shifts as the O/D activates/deactivates.

Done lines flush already.

Thanx,

Any other recommendation?.

Hiroshi

[dksob81]

no thats all I can think of it may have just been the tranny lines and radiator not cooling the tranny fluid.

does the OD ON/OFF tranny shifting still exist after having the lines/radiator flushed.
when I say rad flushed I am not talking about having the coolant part flushed just the tranny part the lines that go into the rad flushed.

[dksob81]

also have you extracted the code (CHECK ENGINE light) to see what the code was.
do this by turning the key ON, OFF, ON, OFF, ON - leave on this time, the CHECK ENGINE light will come on breifly then go out then start flashing, count the flashes. it will flash in double digit code form, with a short PAUSE in between each digit and a long PAUSE between each code.

Example: | = 1 CHECK ENGINE light flash

| pause | | = 12.
pause pause pause pause pause
| | | | | pause | | | | | = 55,

code 12 - loss of power to PCM, battery was disconnected.

code 55 - End of fault codes.

just post the code(s) here and I or someone else will let you know what the codes means.

[HSawabe]

Thanx, I will do that tonight and post the codes tomorrow morning.
And for the flush, I will check with the shop, to know if they have flushed the rad part of the trans lines (they just told me they have flushed the lines).
Do you think I need to flush the rad coolant also?
Regards,
Hiroshi

[dksob81]

no the coolant part should be fine, just the tranny lines section.

[HSawabe]

Today my GC entered the shop again.
They will try to find the problem.
I will let you know if they do.
Thanx.
Hiroshi

[HSawabe]

I almost forgot, the codes I got were:
12, 27, 33, 17, 55

Thanx.

Hiroshi

[dksob81]

you don't have to worry about 12 and 55, (battery was disconnected, and end of fault codes.

27 -One of the injector control ciruit output drivers does not respond properly to the control signal. Check the ciruit.

33 - Air Conditioning clutch relay cicuit. An open or shorted condition detected in the Air Conditioning clutch relay circuit.

17 - Engine is cold too long. Engine coolant tempature remains below normal operating tempature during operating (check the Thermostat). - the thermostat is probably stuck OPEN.

[dksob81]

Have them check the thermostat - this could be related to your OD ON/OFF situation, like I said before if the tranny overheats the it will shut off the OverDrive. this could be related to the Thermostat of the coolant, if the thermostat is stuck open then the coolant will continue to recirculate and cause the engine too warm up very slowly but then once it does warm up it will just get hotter and hotter, because the coolant will not sit in the Radiator long enough to cool down - and the constant heat from the coolant will be transfered to the tranny fluid. HAVE THEM CHECK THE THERMOSTAT!

[jmulkin]

I have the same problem with my wife's GC. Have you found a solution yet? Thanks for any info.

[HSawabe]

No, no solution yet.
My car have been in the shop since Jan,4th and done AT line flush, Rad flush, brought down the Tranny twice checking mechanic and electronic components, changed some sensors, checked all the electric lines/harnesses, without any improvement.
Right now they are changing the TCM... will see if this solves the situation.

I will let you know .

[HSawabe]

Changed TCM... Still the same problem ....

ANY IDEA ???!!!!

NOW I'M DESPERATE !!!!