1998 S70 Intermittent Engine, trans, ABS lights

MikeC · Post by **MikeC** » 11 Sep 2007, 17:17

I just purchased a used 1998 S70. There are usually displayed various combinations of Check Engine, ABS, Tracs, and Transmission arrow lights (sometimes all lights are out!) The local Volvo dealership is stumped. Every fix they do, they test drive it OK, then I arrive to pick it up and immediately get the lights back. Based on the downloaded codes, the local dealership first cleaned the Throttle position sensor and gave it a tune-up (plugs). Didn't work. THen they relaced the TP sensor. Didnt work. Then they 'cleaned' the engine control unit. Didn't work. I understand that the ABS/Trac system is an optional fix (I've seen your posts and plan to replace the control unit). They say on the 1998 models, the transmission doesn't talk to the ABS or Engine control system so they shouldn't be related (I think they are). I asked them to consider looking at the PNP switch (from your forum) but they brushed off the idea. Do I have one, two, or multiple problems here?

Post by **MadeInJapan** » 11 Sep 2007, 18:18

You didn't mention drivability issues. That information would also be helpful as well as the exact codes.

MikeC · Post by **MikeC** » 11 Sep 2007, 19:14

I don't have the codes (dealer mechanic said multiple misfires and a throttle sensor code). The transmission runs smoothly. There is some hesitation/bucking of the car when I try and accelerate. This too varies greatly - sometimes it acclelerates smoothly, sometimes slight bucking, sometimes pretty badly. This doesn't seem like a transmission problem, but an ignition/engine control problem.

Post by **MadeInJapan** » 12 Sep 2007, 05:07

MAF sensor?

jbm · Post by **jbm** » 12 Sep 2007, 07:34

Do you know anything about the history of the car? If all three things started at once then my guess is that there is really only one problem, and it is electrical. Bad connection to the main computer board, or a bad board (ECU)? I am just guessing.

I think you need an experienced Volvo mechanic who can spend some time looking for the real problem. And that might be at the dealership, or it might be an independent. If you take it to someone who just starts throwing parts at it you could spend a lot of money and not fix the real problem.

Post by **MadeInJapan** » 12 Sep 2007, 14:13

Thing is, ABS modules are known to go bad...they throw an ABS/TRACS light. DId this come on before the other things started? And btw, the ABS module when it goes bad, it tends to be intermittent at first, so don't let it throw you that it's on one day and off another...eventually it will stay on all the time if the module is going bad. Also, I have had "coincidental" happenings of several things gone wrong at once even without electrical problems, so I would trouble shoot the specific codes first. You can ignore the ABS/TRACS for now...they won't set the Engine or tranny light anyway. If you're still having strange electrical glitches, then yeah, I would say that something is up electrical and a "real" pro should check things out.