V70 Cruise Control tripping off

My '01 V70 XC has a great cruise control unit, but sometimes when, after
turning on the cruise control control but before setting the speed, the
unit will trip off when you touch the set control (the "+" switch).
Then the cruise control cannot be turned back on with the cruise button
unless you shut the ignition switch off and then back on. The cruise
does this about once or twice a week. It seems to be a random event
that only occurs when attempting to set the cruise. It does not occur
when using the "+" switch to increase the set speed or when using any
other switch.

I have gotten so I can put the transmission in neutral, turn the
ignition off and back on, and restart the engine without slowing down or
stopping, but I would like to get this fixed. I am afraid that the
dealer will just start throwing my money at it like he did when I needed
a pnp switch on my 850's transmission.

I suspect it may be a software problem. I am guessing that the cruise
operates off the main computer. Any hints to help me limit the good
stuff the dealer will replace in trying to solve this is appreciated.

 

PS: I have never had the Throttle Control Module replaced. I don't
know if this could be related to that.

Also, when idling, the engine stumbles. That is the rpm's drop suddenly
from 700 down to about 650 and then jump to to 850 and then settle down.
These stumbles occur about every 15 to 30 seconds or so.

 

If you had a throttle problem the car would stall and you would have to wait a
minute or two before the engine would regain any power. I have been through it...
This sounds like electrical problem. In the fuse box there are two relays that
control cruise control - they labeled 101-102. Check them out...

-Peter

 

Once the computer detects a problem with the throttle module the cruise
will be off until the next restart. Your idle stumble points to this as
being the problem.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

This problem only occurs when I touch the (+) set button. I don't see
how a fuse problem could occur only when I touch the (+) set button.
Once engaged, the cruise works perfectly.

 

Thanks Mike. Once again I think you have solved a problem for me. I
have started experiencing on rare occasions a dead response when I try
to accelerate from a stop. Sort of like when I leave the geartronic in
3 at a stop and expect it to be in 1. It always recovers quickly. I
guess I will have to convince my dealer that I need the TCM replaced
under the extended warranty.

 

I had the similar symptoms with my 2001 V70 2,4T last year. Happened to
be so, that cruise control trips off as a precautionary measure. Thus
there were much serious problems in our car, and voila, after replacing
air flow mass meter AND ETM, the car has been fine.

Goes without saying that hurt my wallet quite a bit.

 

I had a similar intermittent problem on an 2001 V70 2.5 Diesel.
The computer ended up telling me to have the 'Engine management
checked'.
A remplacement of brake and clutch position sensors fixed the problem.