Hello everyone
I have a 2002 S40 1.9T
haven't even had the thing for a year, practically started getting issues the minute i drove it off the lot.

Anyway, right now when i drive, perhaps 20 or so minutes into the drive (city) the ABS and Brake lights come on, and the speedometer drops to 0 and stops working. Sometimes if i drive another 10 or so minutes, itll clear up and the speedometer will start reading again, but usually it stays on untill the engine is turned off and cools for at least 4 hours.

Also, my gas mileage took a dive, used to be at 24.2 mpg, now sunk to 17.3 mpg. This took about 2 weeks to happen, first the gas mileage started to drop, then the abs and brake lights started to show up, and today, the CHECK ENGINE light came on a little while after the ABS/Brake lights came on. After work, i started the car, as usual the abs/brake lights were NOT lit, but the CHECK ENGINE light was still on. Drove the car to the gas station to fill up, after i started to get on my way home, the check engine light cleared too.

I have a suspicion the ABS module may be the culprit (Ive read some articles where people had the same issue with the abs/brake lights and the speedometer, and it seems to be from a cold solder joint) and as far as the check engine light and the gas mileage goes, i think (I HOPE) its just the O2 sensor.

As a side note, a few weeks after i got the vehicle, the check engine light did turn on, so i took it back to the dealer where i got the car, and the guy scanned it, and said the catalytic converter was shot, but he cleared the code, however I did NOT get it repaired, so im not sure if that could have anything to do with this issue (the car ran fine for the rest of the time until a few weeks back).

I dont hear anything wrong with the engine, no gas/exhaust smell, no hesitation, brakes work phenomenally.

Has anyone experience something like this before?

Thanks in advance!

 

The cat converter being reported as faulty was actually a problem with the O2 sensors for my 2001. You have 2 sensors, one before the cat (called upstream) and one after (called downstream). The top one is used as feedback to the ECU to adjust your fuel trims. This one being bad drops your fuel mileage. And too rich a mixture can also overwhelm the cat converter such that the bottom O2 reports a bad cat. Also, if the bottom O2 is faulty it can trigger the check engine light.

O2 sensors should be changed every 100k miles. I've gone 150k before they get really bad and start causing problems. They are easy to change yourself with the right tools.

EDIT: The speedo and abs/brake light problem is new to me so I'm no help.

 

The speedometer/ABS issue is likely one of the ABS speed sensors. That would cause your ABS light to come on and could also cause the speedometer not to work.

 

Thanks! Im having it checked out this saturday, hopefully its nothing serious!