Using Autel AP200 to try ABS brake bleeding my 1999 Ranger 2wd RABS because they said it was compatible, but wasn't & couldn't communicate. It was able to pair up with my phone so it was being powered. Was told to give them the data log, & they say it was an issue with OBD pin 7. The only YouTube video I found on OBD pin 7 was on an Audi A3 with an issue on pin 7 (K line) as well because of a damaged wire. With key off & dongle off the OBD port, there was 0 V on pin 7. Out of curiosity, I did the same test on a 2001 Ford Escape with 4WABS, & pin 7 read 3.9 V & it was able to do ABS brake bleeding. Is the Ranger supposed to have the same voltage reading on pin 7 even though it was RABS? I had tested an Xtool A30M to do ABS brake bleeding & it only worked on the Escape as well. I was able to return the Xtool, get a refund & chalk it up as just having a buggy software. I was told to do a scan with the Autel & send them the data log again to see if I had any ABS issues, but the only codes that came up was B1359, B1431 & B1434. I didn't have an ABS warning light, the wiper was working just fine, & as long as the battery isn't drained, it starts just fine so there's no ignition switch problem.
Is Autel right about ABS compatibility even with RABS for my Ranger & it's just an issue with pin 7 or are they just leading me through a rabbit hole? If so, how can I test & verify it? My Haynes manual doesn't have a wiring schematic for the OBD port that I can follow. Thanks.
On a 1999 2wd Ranger you shouldn't need a scanner to bleed the brakes.
Ford moved the RABS Valve around through the years but by 1999 on the Rangers I think they moved it onto the Driver's Side Fender so I found a picture of one mounted there and added some text to it.
Here's a sketch that may be helpful
The reason you don't need a scanner to bleed the brakes is because the Isolation Valve is "normally open" (allowing brake fluid to pass through the valve body from the master cylinder to the rear wheel cylinders) AND the Dump Valve is "normally closed" (preventing brake fluid from entering the Accumulator) between the master cylinder and the rear wheel cylinders).
The Accumulator is a "reservoir" and let's say your rear wheels start to lock up. The RABS module will command the Isolation Valve shut to prevent any additional brake fluid pressure (as you mash down on the brake pedal) from getting to the rear wheel cylinders and locking up the rear wheels. BUT it still has a problem. There's already brake fluid under pressure back there on the wheel cylinders causing the rear wheels to lock up and closing the Isolation Valve didn't change that.
It needs a place to "relieve" that brake fluid pressure so it temporarily "Dumps" that pressurized brake fluid (By commanding the Dump Solenoid Open) from the rear wheel cylinders into the Accumulator in the RABS Valve Body.
And when the "event" is over the spring in the accumulator pushes the "collected" brake fluid in the Accumulator back into the master cylinder.
So anyway, using any type of scanner there's nothing to command these solenoids to do. They're already doing it in their "((at rest)) normal positions".
But enough with the "in a "perfect world" stuff.
What if you tried bleeding the brakes without a scanner and you couldn't?
Some of those RABS Valve bodies had a bleeder screw on them and you could bleed the brake fluid on the valve body before you started bleeding the brakes.
But a lot of them didn't.
In that case you could try (referring to the pic I added text to), unscrewing the Accumulator Spring Retaining Bolt, Pulling out the spring and trying to bleed the brakes.
IF the Dump Valve isn't leaking, you won't get any brake fluid squirting out of there as you mash down on the brake pedal. If fluid does squirt out of there, you've found your problem
Thank you very much for the very detailed description! I just recently saw a YouTube video about ABS brake bleeding an F150 where he unscrewed a bolt, removed the spring, & manually bled the master cylinder by cracking it open. I was looking for the ABS at the rear & couldn't believe that small thing in the front was it. I was expecting a cylindrical object, smaller than an oil filter.
Anyway, I was wondering if I can remove the bolt & spring & vacuum bleed it from the nipple on the master cylinder instead & reinstall everything back? I've tried that before not knowing that I needed to remove the spring as well. I'd prefer to not squirt out brake fluid everywhere if it can be avoided & not going back & forth on my own stepping on the brake, bracing it & opening the master cylinder. Do I still need to bleed all 4 wheels after this? The YouTube video didn't show him doing that, just the master cylinder.