Error messages ABS, STC, Brake lights on

SimonF · Post by **SimonF** » 01 Aug 2010, 15:20

I have a 2002 S80 2.9 sedan. 141,000 miles.New Jersey, USA. I had a leaking brake booster, bought a used one, installed it and it is now working fine. After I was finished, the ABS, STC, check engine and brake light on the dashboard all came on, as well as and the brake lights on the back are on all the time. In addition, the odometer is not changing. There's also an error message(in the message window) that says: "Brake failure- Stop". I took it to a shop where they put it on the computer, there were two error messages: po571-Brake switch A circuit malfunction and po504 brake switch A brake switch correlation. They shop didn;t know what to do and refer to Volvo dealership. We all know how much this might coast there!
My question: is this an adjustment issue or did I mess up something during installation?. Is there anything I can do (like changing a brake light switch? and if yes how to do that? or do I have to take it to Volvo? Any thoughts or suggestions? Thanks.

Note: the car drives well and the brakes are functioning properly.

stevick · Post by **stevick** » 03 Aug 2010, 08:58

Hard to say what you have there, Simon. The symptoms you have mirror those of the failing ABS module, except for the lights staying on and the codes. Were it me, I would first check the plug into the ABS module. If that didn't do it, I would consider having the module rebuilt (there are many posts on the ABS module issues here). There is an E-bay seller doing the job for as little as $45.00, link: http://cgi.ebay.com/ebaymotors/Volvo-850-S70-S80-V70-ABS-EBCM-Control-Module-Rebuild-_W0QQcmdZViewItemQQhashZitem35ab3bff9aQQitemZ230506102682QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
The posting also has an e-mail contact to help resolve if you would need it or not.

I'm on the road so my manual is not available. As to what's going on with the brake light switch, I can only guess that a stuck or shorted switch is involved. Good luck!

SimonF · Post by **SimonF** » 03 Aug 2010, 20:51

Hi there. Thanks for the advice. O checked the plug and it was loose. The error messages are gone. As for the light I adjusted the switch and it's working now. Appreciate the advice and support