So I've been having some weird problems:

It started with the Brake Failure dashboard message, along with STC, ABS, and Brake lights; I would get this msg infrequently and I would disappear on restart. Then, out of the blue I got SRS service urgent and Service transmission soon messages and NO brake failure message; and I get trouble starting the car sometimes.

I let the car sit a few weeks and today I insert the key into position II and I see the following:
1) The SRS airbag urgent dashboard msg
2) after a second or two, it turns into the brake failure msg (along with the assorted lights) and the SRS airbag msg dissapears
3) The engine cranks, but doesn't manage to start


Next, I connected a cheap OBDII reader, insert the key to position II and I see the following:
1) Now, instead of the brake failure message, I just get the SRS urgent and Transmission soon messages <<<<What just happened here???? I connect the scanner and the dashboard messages change?!>>>

2) I turn the key and the engine starts
3) No check engine, but the srs and transmission messages remain
4) no brake failure message
5) i drove around for a few miles and it seemed fine, i got up to 40,50mph with no trouble, although i didn't try anything faster.


Somebody suggested that it may be the gas pump, so I released the pressure on the fuel rail and tried to start the car....it wouldn't start. Next, I disconnect and reconnect the battery and...it starts!

Right now, i am thinking it could be a few things:
- The abs module malfunctions and causes the computer to throw the SRS and transmission codes OR
- the Gas pump fails and doesn't let the car start OR
OR - the central computer is malfunctioning and affecting the other systems

Can anyone help? I am no car expert.

Thank you
Oscar

edit:
I drive a 2000 s80 with about 140k miles, no turbo.

Update:
I went through the procedure described here: http://www.matthewsvolvosite.com/for...hp?f=11&t=5827

I got these results:
'DTC set' for: ABS, SRS, TCM, ECM, CEM, DIM, CCM, PSM, REM, SWM, UEM
'Ready' for: LSM and AUM
'Checking' for: DDM and PDM

 

There are a lot of possibilities- without having the codes from those modules checked (a generic scanner likely won't be much help), guessing can get expensive.

 

Well, if you had to take a guess....what do you think it could be?

 

I would guess you have more than one problem. A bad ABS control module can cause the transmission service message to come on, but not SRS.

Or you could have a bad CEM.

Battery voltage can be an issue.

Or you could have fault somewhere else in the CAN system (wiring, terminals, etc).

I would not guess the fuel pump, however.

 

Okay, thanks!

Battery voltage seems like easier and cheaper to check. I'll start there.

A few people have also suggested the ABS module...If I took it out, is there a way I can check if it is working properly?

Edit: Also, when I use the OBDII reader, I get codes P1633 and P1631. That leads me to believe it might be the abs mod.

 

Nothing you can test on the ABS control module.

I'm not at work so I can't covert those generic codes to Volvo-specific ones, which may help get a better guess. But there are certainly codes stored in the other modules that a generic scan tool won't read that could be helpful.

 

for anybody wondering, I got my battery replaced. It seems that the low voltage was triggering false positives

 

I had a similar issue just now

Messages
TRANSMISSION FIX
BRAKE FAILURE - STOP ASAP
ABS
CHECK ENGINE

Like the above, it wasn't any of these. My battery is fine so the mechanic added some liquid contact enhancer to the electrical terminals and all appears to be working well again