If your van is a 95 then try this procedure which works from 89 to 95:
Turn ignition on. Use a jumper wire to ground the Service Diagnostic Connector black wire. Maintain the ground for approximately 2 seconds. You should find this single connector under the glove box next to the ABS controller. The flashing of any codes is the same as my post above.

 

Thanks for the reply, however I don't seem to have such a connector in that position (I guess you mean under the plastic tray insert in the glovebox?). From some of the earlier info in the thread I believe this only applies to the RWAL ABS, but I have 4 wheel ABS on this van. Do you know the way to get the diagnostic ABS codes from the 4 wheel abs system?

Thanks,
Ben

 

I am sorry, but I do not know at this time how to pull the 4 wheel ABS codes.

 

Ok I've had another look at this today.

I have located the ABS controller next to the 4 wheel ABS valves, and this has a multiway connector which I assume are the inputs from the wheel sensors and the outputs to the various valves, and a 2 pin connector with thicker wires, which I assume are the power to the controller.
One of the pins is ground, and the second pin measures 10v when the ignition is on. This doesn't seem quite right to me as I would expect to see the full battery/alternator voltage on this pin. I can hear a relay click inside the ABS controller when I plug the connector in however.

Also, I put an ammeter in place of the ABS fuse in the fuse block under the hood - it is reading absolutely zero which again doesn't sound right, as I would expect the controller to be pulling some current when idle. Its almost as if the power from the ABS fuse is not getting to wherever it's supposed to.

Unfortunately though my Chilton manual doesn't have any wiring diagrams for the ABS controller, I don't suppose anyone has a copy of these?

Thanks,
Ben

 

Did some more fault finding today.
I traced the wire coming from the output of the ABS fuse to see where it actually connects to. It took some considerable time, but found that it goes to a relay that is located between the battery and the drivers side headlamp, and the output of the relay appears to go into the ABS pump/valve module.

The relay coil supply measures 12v with the ignition on, the relay clicks when connected to a test 12V PSU, but the relay when in circuit does not click when the ignition is on! When measuring in circuit, the relay coil voltage drops to 0 when the relay is plugged in. So, for whatever reason the coil supply does not have enough current, perhaps a bad ground or driver transistor, depending on where the coil supply comes from.

I tried bridging the switched contacts where the relay would go to see if the ABS light would go out, effectively bypassing the relay. Unfortunately no such luck.

So, I'm a bit stuck now. Anybody got a wiring diagram for the 4 wheel ABS?

Thanks,
Ben

 

Hi guys i know this is a old thread but i am getting frustrated. I have 1995 dodge ram with four wheel abs. I am trying to retrieve codes and took it to a friends shop who said the only way is from the connector under the dash. He showed me the connector and said that he tried to ground it like usual with the key on but could not retrieve any codes at all. So what the heck does this mean . the abs light has been staying on every time i start it up and randomly foes off and on as i drive. Sometimes it stays of until i some to a stop and then goes back on again. I have replaced the rear sensor in the past at least one time and it fixed the problem so i did it again and it worked for a couple of months and now the brake light came on a couple of times. One day both lights stayed on all the time with a long drive. I am just trying to get the codes so i can figure out what is wrong any idea"s. The connector under the dash only has 8 pins but does have the black wire with a white stripe. So i assume ground it for a second or two with the ignition in the on position correct. please help me
rick