W140 security module / no start
 

Im planning to have a look a very clean 1998 S420 (140k) this week, however he says it wont start and when he had it scanned and the security module code popped up. $1500 dealer repair. Does not crank.
What steps do I need to take to fire this thing up in his driveway? Im hoping it might be something simple like the neutral saftey switch or something.

I beleive this car has a metal key blade, its a bit easier than the later items but equally pricey.

I would run the other way. lol. (But this coming from someone that has had problems with a W140 that I cannot figure out, lol).

Good luck!

1998 was the first year of the DAS system and 3 button keys for 140s. If the drive auth system ecu has died, there may be no way to start it. Sometimes d&c of the battery can get the car to start again. Just replaced one of these on a 99 SLK and there was no work around on that car.

Mine had a trouble no cranking,and I would have to hold the key at starting position for 2 monutes before it fired sometimes.It was my k38 relay that was bad.Its under the cover and behind fuses.@nd row of regular fuses.Space F I believe