Volvo V70 engine management light

At first it was intermittent. Then permanently on. Volvo dealer said ECU needed at vast expense. I declined. Tried them again and they said "We have cleared the fault". After leaving the garage and within 20 seconds it came on again. On returning they said it was in fact the auxilliary air valve.By this time I lost confidence and drove the car for 6 weeks or so with no real problem except slight engine "hunting".
A diagnosis elsewhere defines it as the idle control system. They cleared the fault but again within 1 minute it came on again.
The latter people said I dont have the alleged valve on my V70(New December 1999). So I am confused and brassed off with the matter. Any one have similar experience and/or advice please.
Jim

All I can suggest is try another dealer.

Some have better experience than others at various faults.

If that fails, try Volvo CC.

If that fails, write to Auto Express.

I would also suggest finding a specialist forum on the Net. I found one for my Seat Alhambra (read Ford Galaxy) and it has been really helpful. Like this one for DIY, you can glean a lot of knowledge.

My opinion of the main dealers I have dealt with is that most of them know almost nothing except how to rip you off. You might also try to find a specialist as they often very knowledgable. My local porsche dealer sometimes uses a specialist for the difficult stuff!!

Thanks for the comments. An independent diagnosis found it was the idle control motor and the job is done and dusted. So much for Volco dealers !!!!
Jim