Volvo: 2000 Volvo XC70, obd ii reader, volvo xc70

Question
Hi Ray,

A couple of weeks ago, the ABS and Brake lights on our 2000 XC70 were showing intermittently.  We took it to the dealer and they put new rear rotors and pads on and the lights seemed to go away...they said they didn't find any other issues.  Well, on a trip over the weekend, those lights began showing again.  However, this time when they came on, our speedometer stopped working.  This happened after driving at highway speeds for a couple of hours.  Occasionally things would look normal again, but would then reappear.  Next, the transmission starting behaving as if I had pressed the "W" (winter) button and the arrow indicator would blink.  Actually depressing the "W" button did nothing to change the situation.  Since we were travelling on a Sunday when this happened, we just decided to get to our destination.  The next day and on the trip home, none of the behavior was repeated, but the "check engine" light is on.

Any idea what is going on?  Could it be a bad sensor some where on the system or the ECM going bad?  I have a general OBD II reader (not Volvo specific) that reads "NO diagnostic codes stored."

Thanks for your help.

Drew

Answer
Drew,
I would say that the ABS has a fault and that fault is in the control unit and affecting the speedo signal. When there is not a speed signal the transmission control unit does not know the speed of the car and what gear to chose, so it goes into "limp home" mode. That is a high gear that will move the car to a safe place, but offers limited speed and power. If there are not any codes stored then things become difficult. Maybe you only read engine fault codes, see if you can read the braking system.