99 hyundai accent overdrive

My overdrive wont kick in on cold mornings and if it does it kicks in and
out until it runs for aboute 30 minutes. I took it to the transmission
shop and after 15 days they have changed the overdrive bands, oil temp
sensor, pulse generators, saftey switch, and said they have tested
everything and it never throws a code but it still isnt fixed and they
gave up , PLEASE help, i'm out of money and ideas

 

Did they check the overdrive switch on the shifter? There may be a bad
contact inside the switch (or in the wiring going between the switch and
TCM).

 

yea they checked the overdrive push button switch and selonoids , all
checking good. When im driving along in overdrive it suddenly drops out of
overdrive but the light on the dash is still out showing its in overdrive.
I can sometimes slow down then pull it into 2nd gear drive till it revs
way up on the tack then put it back into drive and it will go back into
overdrive. Any other suggestions?

 

Here's how the switch works (when it's working correctly):
It either applies ground to the dash lamp which reads "o/d off" or to the
monitoring circuit of the TCM. If there is an intermittent open circuit
in the switch or wiring, or there's a bad ground, then the lamp won't come
on, and the trans won't shift into overdrive either. If you haven't any
DTC's, then this switch should be the primary suspect.

 

I have the console and switch apart now trying to trace the 3 wires from
the switch to check the ground and wires but the thing is the light will
be off when it is in overdrive and stay off when it kicks out of overdrive
, its suppose to be on when overdrive is off . Also last night I noticed
that when it kicks out of overdrive if I push down on the shift lever it
goes back into overdive for a while what would that show?

 

It would show that you have a break in the switch wiring or a poor contact
in the switch. Replace the switch.

The reason the light doesn't come on is that when there's an open circuit
in the switch or wiring, ground is neither applied to the lamp nor the
trans computer. The job of the switch is to change where ground is
applied. When it doesn't function correctly, no ground at all is a common
occurrence.

 

Hey tech man guess you were right I took the switch apart and wired the
overdrive straight to the ground got a closed curcuit and overdrive has
been on for a week now, only thing is it stays in overdrive but thats ok I
travel highway everyday and transmission shop rebuilt the overdrive
clutches and bands when they were trying to figue it out. I fixed it in 2
hours they couldnt after 18 days and $300.00 . Thanks , I guess I can put
a toggle or some othe swith in now so i can turn overdrive on and off when
i want.