Intermittent ABS/Brake warning indicators and Yellow Arrow

SpaceCadetSD · Post by **SpaceCadetSD** » 12 Mar 2009, 16:58

This is regarding a 2000 C70 LPT Convertible, w/ approx 83K miles. The ABS, BRAKE & 'Yellow Arrow' lights will sometimes stay out for a day or two (CEL is constant) then suddenly trigger again in the middle of driving--and sometimes even kick the car into limp home mode.

I pulled the OBD-II codes and got the following three P0722, P1618 & P1633. There aren't a lot of specifics available to me on these codes (after all, not as if I have a VIDA system at home to read directly from the affected control units)

Are these faults most likely caused by a bad ABS controller or a bad speed sensor(s)? And, if it is likely just the speed sensor, how would I know whether it's the back dual sensor or which of the front left/right sensors?

Thanks for any insight!

Post by **MadeInJapan** » 12 Mar 2009, 18:10

Yes, those codes are most likely due to a bad ABS module:
P0722- Output Speed Sensor Fault
P1618- Fault in Lead Between AW 50-52 and Motronic ECU
P1633- VSS (Vehicle Speed Sensor) Fault
Because everything goes through the ABS unit in relation to the codes you get (although P1618 is questionable), I would say that it is your ABS unit. When it goes, strange things begin to happen. Have it rebuilt and reset your codes and you should be back to normal.

SpaceCadetSD · Post by **SpaceCadetSD** » 12 Mar 2009, 18:37

Okay I'll get on top of fixing the ABS controller ... can't have my speedo keep cutting out randomly and losing acceleration in limp home mode.

My follow-up question though is about clearing the codes ... can I simply clear the codes via my OBD-II reader once the rebuilt/new unit's installed, or are the faults stored in the actual subsystems? Will they trigger again unless cleared by the dealer or a shop with a VIDA link?

Thanks Again MIJ!

Post by **MadeInJapan** » 12 Mar 2009, 21:20

Look at Victor Rocha's site: http://home.earthlink.net/~vicrocha/
It explains a lot of what you ask. If I recall, I just pulled the fuse (or was it a relay? Anyway, it's on his site) until the rebuilt ABS unit came back...when I hooked it up an replaced the fuse/relay and after going about 35mph, the ABS light and trouble codes went away on their own. Be aware that you'll need the small E5 reverse torx socket.