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ABS & Brake Light Turns on for No Reason...

5K views 4 replies 3 participants last post by  Izzy 
#1 ·
Kelsey-Hayes Antilock Brake Systems:
The EBC 325 ABS system uses one wheel speed sensor on each front wheel, and one speed sensor mounted in the rear axle for the rear wheels.

The RWAL II uses only one speed sensor mounted in the rear axle for the rear wheels.

The sensor measures the wheel speed by monitoring a rotating tone wheel. The signal generated by the sensor and tone wheel is transmitted to the CAB.

Each sensor has:

a metal tone wheel with teeth on its outside diameter
a magnetic/coil pick-up (speed sensor) that is mounted to a fixed component
an air gap between the tone wheel and the speed sensor assembly
As the teeth of the tone wheel move through the magnetic field of the sensor, an AC voltage is generated. This signal frequency increases or decreases proportionally to the speed of the wheel. The CAB monitors this signal to check for a sudden change in single or multiple wheel decelerations. If the deceleration of one or more wheels is not within a predetermined amount, the antilock module takes control.

Diagnostically, the coil of wheel speed sensors have different amounts of resistance based upon the sensor type. When measured across the connector two terminals, the resistance should be:
AN, DN, BE and BR:
4x4 front sensors 945-1155 ohms
AB, AN and DN:
4x2 front sensors 2500-2955 ohms
BE and BR:
4x2 front sensors 1000-1250 ohms
AB, AN, DN, BE and BR:
All rear sensors 1600-2300 ohms

NOTE: For all resistance ranges add 30% to the value for extreme heat, subtract 30% for extreme cold.)

The rear wheel speed sensor used on all vehicles have the same resistance value, but there are two different sensors. Therefore, it is important to replace the rear wheel speed sensor with the proper part.

On a EBC 325 system each front wheel speed is monitored through the speed sensor mounted at the wheel end of the hub. On a EBC 325 and RWAL II system the rear wheel speed is monitored through the speed sensor mounted in the rear axle assembly.

The CAB will disable antilock control, illuminate the ABS warning light circuit via COD, and store trouble codes if it detects a problem with any or all of the wheel speed sensors:

*incorrect circuit resistance when checked with no vehicle movement
*incorrect sensor output during vehicle movement
*erratic sensor output during vehicle movement

Rear Wheel Speed Sensor Replacement
REMOVAL

-Raise vehicle on hoist.
-Remove brake line mounting nut and remove the brake line from the sensor stud.
-Remove mounting stud from the sensor and shield.
-Remove sensor and shield from differential housing.
-Disconnect sensor wire harness and remove sensor.

INSTALLATION

-Connect harness to sensor. Be sure seal is securely in place between sensor and wiring connector.
-Install O-ring on sensor (if removed).
-Insert sensor in differential housing.
-Install sensor shield.
-Install the sensor mounting stud and tighten to 24 Nm (200 inch lbs.) .
-Install the brake line on the sensor stud and install the nut.
-Lower vehicle
-Have a great day! :D
 
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#2 ·
More Questions behind ABS situation

Hi, Pete here,might you be a dodge certified tech? ifso I need some help if possible. I have same prob abs & brake lamp on I changed rear abs sensor already I have 96 dodge ram 2500 4X4 heavy duty dana's frt & rear 8800 gvw, yet lights still on . Another tech told me to change dump valve assy under master cyl but brake lines are soooo coroded I'm affraid of cracking them loose, I called local dealer to get replacement lines & they told me I would have to buy a roll of tubing & make new ones. Is this true? are lines not available? my second concern was a bad brake light switch because brake lights would stay on I also changed it & abs light & brake light on dash still on. I noticed small ground wire on base of dump valve & master is burnt from possible high amperage? maybe don't know can you help me diagnose this ? I tried to get codes w/ snap on scanner but can't seem to get system to retrieve codes . Do I use diag cconnector under hood or obd2 connector under dash, or any other manual way of getting codes. my e-mail is Spotbowl@aol.com, or post here
 
#3 ·
Aloha Pete:

Sorry I'm not a Dodge Tech, I'm a Network Tech, that tinkers with his Durango, but if you have good breaking and not DTC in the PCM, then I would trace down the wiring issue you brought up b4 changing the line...and if the brake lines are that rusty FOR THE LUV OF GOD CHANGE THEM OUT!!!

Just remember:
If any of the following exisit:
-incorrect circuit resistance when checked with no vehicle movement
-incorrect sensor output during vehicle movement
-erratic sensor output during vehicle movement
the lites come on.

DTC should be read with a ODBII Scanner (connections under the dash), did you test to see if your ABS is actually working with the lights on....dont do it on a busy street and get a buddy to help you. see if the wheels lock or not. I'm not sure about your lines.


I wish I can give more, but that's the best I got right now....did you check the tech thread for Rams
 
#5 ·
Aloha tyretzlaff:

Glad to have helped. Enjoy the truck! :D
 
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