So...got the A2 142 code. Changed out the brake light switch. Contortions and all. Still have ABS light. Cleared code. Still have code. WTF.
1995 850 10v.

 

DTC 1-4-2: FAULTY BRAKE LIGHT SWITCH, OPEN OR SHORT CIRCUIT

1) Check if brakelight works. If brakelight does not work, check bulb and wiring as necessary. If brakelight works, connect test box to control unit. See Fig. 3. Connect voltmeter between test box terminals No. 32 and 1. Depress brake pedal. If voltmeter indicates battery voltage, erase DTC and test drive vehicle. See
TEST DRIVING VEHICLE under DIAGNOSIS & TESTING. If DTC occurs again, replace control module. If voltmeter does not indicate battery voltage, go to next step and check if circuit is open or shorted.
2) Remove 2 wires (Red and Yellow wires) from brakelight switch. Connect voltmeter between Red wire and ground. If battery voltage is present, go to next step. If battery voltage is not present, check wiring or fuse for an open circuit.
3) Connect a jumper wire between Red and Yellow wires. If brakelight lights, ensure brakelight switch is adjusted correctly. If switch is adjusted correctly, replace switch. If brakelight does not light, ensure wiring to brakelight bulbs is okay.



Read more: Volvo 850 ABS & TRACS service manual

 

Well...trying to find the solution to the a3 code 142, I found a ground connection not installed. Plugged it in...some clicks and bumps from the engine bay...and now I get the 444 code. Did I inadvertantly fry a relay or some such?

 

possible. 444 means no power to the ABS valves so you either blew a fuse, have a bad relay or bad connection/connector somewhere.