Second Time ABS/Tracs Strangeness

Post by **rmmagow** » 26 Jul 2012, 10:03

OK, I am familiar with the ABS/TRAC Matty-Moo fix (and will probably do it)
My ABS light will go one once in a great while, say every 2~3 weeks which equates to once in 1500 to 2000 miles. Speedo never mal-functions regardless. Air tire pressure is OK I think, checked less than a month ago.

Is this the classic ABS related failure? Are the sensors tough to remove and clean? For the peace of mind, I think I'll send the ABS thing out for the fix. The light goes on, but the next time I start the car it is off and stays off for a long time.

byeboy · Post by **byeboy** » 26 Jul 2012, 10:11

Please post the link to the Matty-Moo ABS/Tracs Fix. Thanks!

Post by **jimmy57** » 26 Jul 2012, 10:16

For every wheel sensor problem that is really a wheel sensor issue there are 100,000 bad modules.
Get the module fixed first.
One of the areas where the circuit board to connector pins solder crack usually is the wheel speed sensor inputs.
The speedo will function if one of the rear sensors still connects.
The reason the light comes on can be several things other than the wheel sensor circuits. Regardless, the module failure rate is 100% in time unless the module stays in a box on a shelf. The heat cycling with its location in engine compartment cracks the lead-free solder deposited very thinly due to the original manufacturing process wave soldering. NOT exclusive to Volvo.

Post by **Matty Moo** » 26 Jul 2012, 10:41

Exactly what Jimmy said.

the LF wheel sensor pin ALWAYS cracks first. It's on the edge of the board. The two pins for the pump motor usually go right after that. Then they work their way up from the edge of the board.

when I scan the LFWS code comes up at least 95% of the time, followed by the pump motor, then RFWS and sometimes the rears. Depending on the combination of what is cracking, then the communication codes come up. On a module that's been let go for years it's not uncommon to come up with a handful of codes.

For what it's worth, they used the exact same system on a lot of different cars, it isn't Volvo's design. Dodge Neons, Rangers, VW's, Jags, Grand Cherokees, Dodge Caravan...etc.

Could they have spec'd out something better? Not really, just about anything from that era has it's own flaws.

Post by **rmmagow** » 26 Jul 2012, 10:49

OK I'll send off the thing to be fixed. I need to find that weird torx thing, but I know I have one from my earlier V70. Funny you mentioned Jag, I had a Jag a few years back and had the ABS computer fixed on that, now I know why all this looks familiar.

Post by **jimmy57** » 26 Jul 2012, 11:58

"Could they have spec'd out something better? Not really, just about anything from that era has it's own flaws."

The bad part of this is that wave soldering of electrical boards is still done and the issues are still there but luckily fewer.

They learned to flux spray the areas and to clean insulation off in a larger area but engine bay CM's still have those failures. A brittle metal and things that have different thermal expansion rates with no allowances for that (off the shelf resistors, caps, etc) still crack in time.
The engine control computers on several diesel engines are block or rocker cover mounted and there is a cottage industry to repair those too. I'm not complaining. I'm repairing those regularly on Ford 6.0 diesels.

By the way, a lot of the evaporator failures are oven brazed caused cracks and corrosion. The process to make evaporators uses flux coating on the aluminum pieces and flux residue leads to external corrosion and the brazed areas are thin and crack. Evaporators are replaced regularly on LOTS of vehicles, 800 platform Volvos are in good company on that failure. The OB process has been improved.

Post by **niles** » 26 Jul 2012, 18:52

My ABS and Trax Off lights have started coming on in the past week. They go out periodically and then come on again. Sometimes this is accompanied by a whine and pulsation at the brake pedal, kind of like one can sense the system disconnecting. I ran the code reader, but nothing comes up. Is this my module going bad? In the last month I soldered in a diode to relieve code P0410, SAS malfunction, according to instructions in another part of this website. That kept the CEL from coming on for 2000 mi, but it has recently come on again. If I delete the code, the CEL goes out for 200 mi and then comes on again. Could this jumper fix have something to do with the TRAX and ABS lights coming on? '98 S-70 GLT, 105 K mi.

Post by **jimmy57** » 26 Jul 2012, 18:59

A generic OBD-II code reader only accesses the engine computer and a limited access to the transmission computer. Those are the only two with emissions implications.
You are listing the symptoms of the ABS module faults. If you do not know of the ABS module being replaced before then I would suggest Matty Moo repair/exchange and then see if the light comes back to indicate it needs other repair.