My ABS light is glowing on the dash. I think it could be a case of dirty wheel sensors.
So I found some info about the diagnostic unit on Brickboard, but I only have one diagnostic unit on the left strut tower, and it's not labelled "A" or "B".

I read I am supposed to pull the code from position "A3" but that spot is a
"dummy" and no connector is down inside it. The only "real" spots in my diagnostic connector are "position 2" and "position 5"

"Position 2" had no codes.
"Position 5" threw a "2-1-4" code, not sure what this means. Are you?

Here's what I'm planning to do unless I hear otherwise:
Turn the car's front wheels all the way left and reach behind the brake rotor and loosen the sensor from the back of the rotor shield, brush it off and re-install. Then turn the front wheels to the right and repeat on the other front wheel. Then I'll disconnect the battery for 15 minutes to clear all codes.

Any ideas???

THANKS.....

You can't read ABS diagnostic codes on a 240. Does your ABS system deploy unexpectedly, or is it just that the ABS light is on? If the former, this might apply:

The ABS on my 93 acted up a while back. When I would come to a slow stop, the ABS would deploy right before the car stopped. The problem turned out to be a worn tie rod that allowed the wheel to wiggle a bit, just enough that the ABS system interpreted it as wheel spin. I replaced the tie rod and the problem was solved. It surprised me because the amount of play was very small. Cleaning the sensor could also help, but to do a really got job, remove the rotor and clean the reluctor (toothed) wheel on the back.

If the ABS is not deploying but the light is always on, check the fuse. The ABS computer is under the passenger seat near the front (moved from earlier years). You have to take out the seat and pull back the carpet to get to it. There is a fuse in the front of the unit. Make sure that fuse is not blown. FYI, removing this fuse will cause the ABS system to be inactive, but the light will stay on.

Let us know how you finally fixed it.

The 93 240 OBD-I only reads codes for F/I and IGN faults. Positions 2 and 6 I beleive. Newer volvos, I think some 94's and up use the OB-II that will read ABS codes. On your 93 the ABS codes have to be pulled up remotely like the SRS system.

Read the 700/900 FAQ on this site, for the codes, and how to erase them. You don't need to disconnect the battery; you can erase them using a procedure that makes use of the button on the diagnostic unit.

The wheel sensor wire could be split somewhere, or there could be another problem. Cleaning the sensors won't hurt. Watch out for the o-rings on the sensors, to make sure they're seated properly. I usually grease the O-rings a little bit on reinstallation.

The 2-1-4 code is an RPM signal missing. It could be time to replace the crankshaft position sensor.
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chris herbst, near chicago