Hello
I have a s40 2003 1.8 petrol automatic{my uncles car},that in the 6 months he owns the car it has failed to start 4 times,yesterday was the 4th occurance where he drove to a meeting parted for two hours and got back in and it would not turn over..
Turn on the key and no dash lights come on..the steering lock unlocks,windows,lights,wipers all operate correctly but turn the key and the car does not turn over..
On the first occasion I disconnected the battery for 10 mins reconnected and it started{just luck I think},on the second and third occasion the car was parked up for a week to two weeks and rectified its self..
It is a very strange one and it does the exact same problem every time it happens
I had checked the ignition connections,fuses,fuse box and a rough look around the wiring to see if I can see anything ovious..
There has been an airbag light on for the last 4-6 weeks but I cant see how it would affect my starting problem..
He had the car two weeks and I had to replace the fuel pump in the tank as it died..{just thought id mention it}
This car was a one owner car with full service history from new when I picked it up for him..
ANY HELP WOULD BE GREATFULLY APPRECIATED AS MY UNCLE IS DOING MY HEAD IN...

Thanks James

 

The key is that the dash lights (etc.) don't come on but other things still work. That eliminates the battery or main cables.

About the only way you're ever going to find this problem is to troubleshoot it while it's in the failed mode - and it sounds like that's going to be pretty difficult. I don't have any schematic for your car, but if there's a relay that supplies power to the dashboard, I'd swap it out as a "shotgun guess", since relays are a lot more prone to fail than connectors or fuses.

 

not sure I follow - if you turn the key to position 2, you get accessories but not the dash lights? and when you turn to position 3, nothing changes?

Sounds like an ignition switch issue but you may want to probe the fuse box/relays to see why the dash lights don't come on with the switch. What happens when you try to lock/unlock the doors with the key fob? (btw, lock/unlock 5x with the fob is a way to get the immobilizer to disengage...). I suppose you can try a jump start but that wouldn't explain the no dash lights. What happens when you wiggle the key in the ignition switch?

 

Wiggle ignition,took steering colum covers off to inspect wiring and plugs and can’t find anything obvious wrong.fuse board has power at all fuses used both sides where required,turn the ignition to the on position and everything powers up in the car as normal but I have no dash/ignition lights and I know the car is not going to start at that stage!battery perfect,starter perfect not that they can cause my problem anyway as the problem won’t let the power go down to the starter because the ignition is not coming on.
p.s I am a construction plant fitter/mechanic by trade so hope I have an idea what I’m at 😲4 times in 6 months this has happened

 

Relay supplying the dash could be worth looking into!i can nearly guarantee if I leave the car a few days and go back to it it will work again which is the annoying thing.
well the real annoying thing is my uncle who drives it,the car is immaculate and has years left in it but not worth getting an auto Electrican to spend a fortune looking for the fault in it.
whatever the issue is,it does the exact same thing every time it won’t turn on

 

not uncommon for a 17 year old car to get connector issues. Given the lights are off, it should be pretty straight forward with a wiring diagram to probe for a failed component or a connection issue. I'd start with the easy to access points (like the fuses and relays) to see where you have volts and check ground points as well.

 

It has happened to my 03 Volvo S40 few months ago. I changed the PNP switch or gear position sensor and now the no start problem is gone. If the PNP switch is not on the park position, the car will not start or no response at all. This is my suggestion, good luck.

 

If you suspect the PNP switch, you can try doing a "shifter row" (park to lo to park 10-20x fast) to see if that will scuff up the contacts in the position sensor enough to allow the car to sense its properly in Park to allow a start.