Colorado Overdrive Dropping Out

[wainstones]

After nearly 9 years and 160K mls of caring for my Colorado 3.0VXTD it has started to let me down for only the second time (first was the well documented cyl/head cracking at 72K) but I'm looking for some help.

On the motorway yesterday and today, at 70mph, the overdrive unexpectedly dropped out without the dash orange light coming on. By selecting overdrive to off the dash light illuminated then on and the light went out but overdrive was still not in. After approximately 5 minutes, overdrive went back in of its own accord. This occurred 4 times during a 600ml round trip.

I've seen on some other posts talk of the solenoids on the gearbox - especially one which is the speed sensor. Could this be the problem?

Any comments gratefully received.

[Andy]

Could be the speed sensor as you say, also could be the engine temp sensor which is just above the starter motor.

[Teknys]

Hi/Lo detection switch LH side at top of transfer box blue connector water in connector or actually in switch.

[wainstones]

Hi/Lo detection switch LH side at top of transfer box blue connector water in connector or actually in switch.

Thanks Teknys - you sound like you speak from experience. I spoke to my local garage (not Toyota) yesterday and he was going to plug it in to their system to look for fault codes but as an intermittent snag it could be difficult. I'm seeing him on Tuesday and I'll take a note of your comment with me so we can look at this switch together. I'll let you know the outcome.

[wainstones]

Just come back from the garage who plugged a magic system into the car for diagnostics. Unfortunately it found no fault.

Teknys I mentioned your theory of it being the hi/low detection switch on the transfer box but Toyota do not have a switch with that name. What experience do you have of this fault? If you had the exact same symptoms and changed a component, do you have the part number?

The only advise I left with was to give the gearbox a precautionary oil change and see what happens next. Any other thoughts would be appreciated.

[Andy]

What colour is the ATF in the box.

[Andy]

Any other thoughts would be appreciated.

Water temp sensor.

[wainstones]

What colour is the ATF in the box.

When the garage were having a poke around the other day they said that the level was good and that the fluid looked normal. However, ATF was last replaced in Jul 05 at 115,000mls and since I'm now on 160,000mls changing it is worth a try.

[Andy]

I still think it could be related to the water temp sensor, not the gauge sensor.

If you PM me your email address I have some PDF files for auto box diagnostics.

[wainstones]

Thanks for the files Andy. I can already see what you mean regarding the water temp sensor but I'll keep reading and let you know where I go next.

[Teknys]

Hi/Lo switch is actually called lock switch No1 part number 84222-35080 about £40

Just disconnect switch connector to prove this is that cause.

switch.bmp

[Teknys]

Hi/Lo detect switch, prohibits overdrive if in lo gear. diff lock switches prohibit ABS as well.

Switch is open circuit when in hi range and closed when in lo range, therefore you can just disconnect blue connect which will keep circuit open and prove if the switch is at fault.

[wainstones]

Just for completeness:

After the garage had changed the ATF, they found that the turbo/air hoses had leaks and needed repairing - and come to think it, the car had seemed a bit sluggish on the journey when it had the original overdrive problem.

All seems OK at the moment but I'll not hold my breath.

[wainstones]

And now for closure:

After 1000mls including motorway cruising - all appears well. So those turbo/air hoses must have been the cause after all!