Flashing lights - ABS lights and gas gauge jumping

firefly · Post by **firefly** » 24 Sep 2009, 19:01

The ABS lights on my 1999 S70 almost continually flash and periodically the gas gauge jumps. Are all these controlled by the ABS module or do I need to quickly trade in? Also the ride is extremely rough. Can anyone help?
Thanks.

Post by **misha** » 24 Sep 2009, 19:18

When you said gas gauge...did you meant on speedometer?
If you did...then YES.Signal for speedometer goes through abs/tracs unit.

If you meant at fuel gauge...then i'm not sure.

firefly · Post by **firefly** » 24 Sep 2009, 19:38

no. it's the gas gauge.
Thanks.

Post by **Ozark Lee** » 24 Sep 2009, 19:47

A flashing ABS light is rare as is the fuel gauge problem. I would start by checking the connector to the instrument cluster but at the end of the day your cluster itself may be on the way out. Sadly the only accurate way to diagnose it on your car requires the Volvo specific scan tools.

...Lee

nightc1 · Post by **nightc1** » 24 Sep 2009, 21:35

When my ABS unit started acting up it would also affect my gas gauge. Sometimes it would drop 2 gal without batting an eye and then pop back up. My ABS & Brake lights both came on as part of the ABS module failing. ON rare occasions only the ABS would come on... but in those cases the speedometer, gas gauge and shifting didn't become issues.

My guess, and this is only a guess, the ABS unit has a bad solder joint that is connecting and disconnecting with the vibration of the engine causing the light to flash. You can disable the unit by pulling the fuse for it under the hood. This will also disable the speedometer but the gas gauge may straighten out. Plus you can drive the car around and see if this narrows down the problems to that unit. You could still have issues that are in the dash, but the signs you are posting are what I experienced with my ABS unit failing.

As for the rough driving, when the ABS unit goes out the transmission tends to lock into a gear and has problems downshifting. This makes driving difficult if it goes out while above 2nd gear because as you slow down it becomes difficult to get back up to speed. Sluggish is almost an understatement when this happens on the highway and you take an exit and stop and then try to get going. Before I fixed my ABS unit using the guide on this site I would down shift to L when coming to a stop if the ABS went out while in an upper gear. If I came to light just starting to turn red I would at times put the car in neutral, turn the car off, and crank it back up as this reset the transmission. So if the ABS+Brake lights were on, at least I could get going again without issue.

If the ABS is disabled from the fuse then the sluggish driving should disappear (along with the Tachometer, Tripometer, Speedometer, Cruise Control and if you have the trip computer the Average MPG, Current MPG and I think average Miles Per Hour... but oddly the remaining Miles setting should still work). For my 99' V70 (base model - aka no turbo) every 1000 RPM's was around 25.5mph after getting up to speed. So 51 was at 2000 RPM and ~76.5 was at 3000 RPM... which made around town driving while remaining near the speed limit possible (and this went on for 2 years before I found that I could fix it myself).

Hope this helps.

If you decide to have any soldering skills or have a friend that can solder and you don't mind DIY stuff... this is possible to do at little to no cost (if you have the socket and soldering iron needed).

firefly · Post by **firefly** » 28 Sep 2009, 20:20

Nightc1, thank you for your input. makes perfect sense. I've heard a great about Vic Rocha online so I may just remove it and send it to him.. I did some reading about soldering those connections and I think some of them may be a bit tricky.
I was looking at getting rid of it because of those issues but I may just wait a while longer!