Speedo haywire on 1996 850 Turbo Wagon

Hi everybody! :) I'm new to the site, but I've been reading around for more than a month. The problem I have is the following: I had the ABS and TRACS lights constantly on. I repaired the ABS control module following the instructions found in this forum (Thank you for posting them!). Now, I have another problem; my speedometer goes randomly haywire (falls on zero and back to normal intermittently) and my odometer stops working at the same time. I know that the speedo/odometer signal comes from the ABS ECU on one wire. Could you tell me what wiring to check so I can eventually bypass it, please? Thank you in advance! :-) P.S. I have a Volvo 850 Turbo Wagon, 1996, engine B5234, 2.3L

Speed signal from ABS is on a Ylw/Brn wire from terminal 6 on the ABS ECU to terminal A3 at the instruments. Suggest you look at the connector on the ABS unit as this will have ben disturbed.

Thank you Chris! :) Any chance the wire would be cut and I need to by-pass it? Cheers, Marius

If the problem started when you repaired the ECU I would guess that the connector at the ABS ECU has a poor contact or maybe the soldering has distrubed the joint in the ECU itself.

Hi Chris! :) I checked that signal wire (yellow/brown) and it's ok from the ABS ECU into the instrument cluster. I think the problem occurred before as well; why? Because before repairing the ABS ECU, my radio volume used to go up when accelerating and go down when braking. Right now, this is what happens: speedo/odometer works normally and all of a sudden falls to 0 and back to normal within a second or two; it may stay at 0 for 1 - 2 minutes and get normal after. When this happens, speedometer, odometer, cruise control won't work and the radio volume is at half (of what it was when speedo/odo works). Is there any chance that my cluster is defective? I'm thinking at that digital 48 pulse output. Today I'll try to do a test drive. I'll attach a voltmeter to the yellow/brown wire and see what voltage comes out. BY the way, what values should I have under normal operation, please? Thank you all in advance! Cheers, Marius

the electrical plug to the ecu is definatley fitted correctly?....maybe a clean of the plug should be done... the only other thing i can see is that when you re-soldered the ecu board joints one was not done correctly..... cheers jod