ABS Warning Lamp> Troubleshooting/ Diagnostics..

[RobBeck]

My car has been hit with the ABS light. The light seems to come and goe with weather, etc. When I start the car in the morning, it will remain off until I drive it to about 25mph... then the light will ignite and not go off leaving my ABS inoperative. Later in the day, it may never turn on or may pull the same thing again. I am pretty sure it is one of the 4 ABS sensors.... but dont want to replace all 4 when likely only 1 is bad. I need to find out how to pull my own diagnostics out of this thing... anyone got any info on how to do this without the Ford Rotunda scan tool? Like with a jumper wire or something, equivalent to the EEC-4 test.... or any other standard way to test the sensors would work to (ohms, etc.)

Thanks,
Rob

 

[SHODWN]

with the ING off they all should be between

0.8-1.4k ohms

 

[rangerj]

RobBeck,

With the ignition OFF disconnect the 55 pin connector from the ABS electronic controller.

For the left front ABS sensor test the ohms resistance between pins 30 and 48 with an ohm meter. See the wiring diagrams so graciously provided by Bizzy to identify the pin locations.

Also check for continuity between pin 30 and body ground. If you get continuity, either the sensor is grounded out or the harness is grounded. The next test will tell us which.

The resistance should be between 800 and 1400 ohms, or as stated by SHODWN 0.8 to 1.4K ohms. Do the same test at the left front sensor plug, between the sensor plug pins.

If the first test is out of spec., but the second test is in spec., then the sensor is OK, but the harness before the sensor plug is a problem.

Next check at each sensor plug pin (sensor side) for continuity between the pin and the vehicle ground. If you get continuity, replace the sensor.

Check the ABS sensor ring on the axel for any broken teeth, cracks, or other damage. Check the front wheel bearing for excessive end play.

Next you are going to do the above test for the other sensors.

Right hand front pins 29 and 47 of the 55 pin connecter. Pin 29 and body ground.

Right hand rear pins 27 and 45 of the 55 pin connector. Pin 27 and body ground.

Left hand rear pins 28 and 46 of the 55 pin connector. Pin 28 and body ground.

The above will give you a check of the harness from the 55 pin connection to the 4 sensors, and a test of the harness to the sensor connector, and a test of the sensors.

There are another 40 to 50 test of various elements of the ABS system. If the above does not solve the problem we'll go back to square one! rangerj