- I drive a 1996 850 plain jane wagon, nothing special and right at 80000 miles – it does not have TRACS (the winter package). Most recently I have experienced a shuddering in the rear brakes – and only at the rear of the car. All pads/rotors are good. The shuddering only happens in slow traffic where you start/stop or need to slow crawl a lot (as dictated by fickle traffic). I thought it was just my wife’s technique of driving. It happened to me. Only once did the ABS light up.

How does one get an accurate diagnosis of just what the problem is? A new ABS pump is expensive. The car brakes solid and true/ and secure. The OBD fault code indicated the ABS pump. There were no other ABS codes indicated. No sensor related codes. No loose assemblies/components either. No controller/computer/or control unit codes (ABS module) either. Sometimes maintenance terms and parts descriptions vary, but actualy seem to address the one in the same item – adding to the confusion.

I disabled the ABS pump (or thought so by removing fuse 29) – only to have the ABS light come on and then no speedometer functionality. But, the car did not shudder during braking operations. Then I find out there are some four (4) total fuses that affect ABS and only 2 are noted in the "drivers" handbook. Dealers do not seem to be more expert.

I have spoken to several Volvo experts (that I trust) and all have a different analysis of how to proceed. In any event they say I should not buy a new ABS pump - but get a used one. Even 2 of them (at Volvo dealers) agree on that. If that is the case I have the Torx socket E5 and rachet and can replace the unit – then re-bleed the whole system. Is it that simple? What have I not considered?

I could use some help and would really appreciate some feedback.

CRD