ABS/brake light

[Towrigdually]

Ive replaced the rear sensor with a new from Napa and rock auto. Still no change. I can clear the codes and the lights go out momentarily then come right back on.

The fuses for the abs system are good also, as are the underhood connections, along with the connection at the rear axle the pigtail is in good shape. 

the 74 code will come and go if I just sit with the truck running and scanner hooked up. 

 

Has anyone else had these codes with similar issues?

Edited January 7, 2019 by Towrigdually

[Mopar1973Man]

Ohm test you rear speed sensor wiring. Check for the open wiring.

[Towrigdually]

Truck wiring at 5.60 ohms while the sensor is at 18.14 ohms

[Chris O.]

This is from my CCD bus tool notes.

When Monitored and Set Condition: REAR SENSOR OPEN
When Monitored: Ignition on. The CAB monitors the wheel speed circuit every 7
milliseconds (ms).
Set Condition: If the CAB detects an open or shorted wheel speed sensor circuit, the
Diagnostic Trouble Code (DTC) will set.

POSSIBLE CAUSES:

REAR WHEEL SPEED SENSOR OR CONNECTOR DAMAGE
INTERMITTENT DTC
REAR WHEEL SPEED SENSOR (+) CIRCUIT SHORTED TO GROUND
REAR WHEEL SPEED SENSOR (-) CIRCUIT SHORTED TO GROUND
REAR WHEEL SPEED SENSOR SHORTED TO GROUND
CAB - INTERNAL SHORT OR OPEN
REAR WHEEL SPEED SENSOR (+) CIRCUIT OPEN
REAR WHEEL SPEED SENSOR (-) CIRCUIT OPEN
REAR WHEEL SPEED SENSOR (+) CIRCUIT SHORTED TO VOLTAGE
REAR WHEEL SPEED SENSOR (-) CIRCUIT SHORTED TO VOLTAGE
REAR WHEEL SPEED SENSOR CIRCUITS SHORT TOGETHER
REAR WHEEL SPEED SENSOR RESISTANCE OUT OF SPECIFICATION

 

Measure the resistance across the Rear Wheel Speed Sensor (+) and (-) circuits at the
CAB connector.
Is the resistance 1600 - 2300 ohms?

 

 

When Monitored and Set Condition: SYSTEM CONTROL MODE TIMEOUT

When Monitored: Vehicle in antilock control mode. Vehicle speed above 6 km/h (4 mph)
for 2 seconds.
Set Condition: When monitored conditions have been satisfied for 120 consecutive
controller checks spaced 1 second apart.
POSSIBLE CAUSES

CAB - NO RESPONSE TO INPUT
BRAKE LAMP SWITCH
BRAKE LAMP SWITCH SENSE CIRCUIT
CAB INTERNAL FAULT

 

ACTION:

in Inputs/Outputs, read the Brake Lamp Switch state.
Apply and release the brake pedal.
Does the Scan Tool follow the pedal position?

 

Edited January 8, 2019 by Chris O.

[Towrigdually]

23 minutes ago, Chris O. said:

Measure the resistance across the Rear Wheel Speed Sensor (+) and (-) circuits at the
CAB connector.
Is the resistance 1600 - 2300 ohms?

 

in Inputs/Outputs, read the Brake Lamp Switch state.
Apply and release the brake pedal.
Does the Scan Tool follow the pedal position?

 

 

Where is the CAB connector exactly? Or what is it?

 

I'm not sure if it follows but I can check.

[Chris O.]

I did edit the post above with ABS connector and multimeter picture.

GLOSSARY OF TERMS:
ABS antilock brake system
CAB controller antilock brake
CCD Chrysler Collision Detection
DLC data link connector
EBC electronic brake controller
EMF electromotive force (generated voltage)
HCU hydraulic control unit
IC integrated circuit
NVRAM non-volatile random access memory
PDC power distribution center
RAM random access memory
RWAL rear wheel antilock
ROM read only memory
WSS wheel speed sensor

 

WHEEL SPEED SENSORS:
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 EBC 2 used 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 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:
4x4 front sensor 893-1208 ohms
4x2 front sensors 1800-2200 ohms
All rear sensors 1600-2300 ohms.

Edited January 8, 2019 by Chris O.

[Towrigdually]

when I read the abs CAB connection I read nothing. 

 

And when the brake pedal is pressed while running the scanner shows, 37 intermittent systems control module timeout

Edited January 8, 2019 by Towrigdually

[Chris O.]

12 minutes ago, Towrigdually said:

when I read the abs CAB connection I read nothing. 

Well it could be the wiring harness, measure the resistance directly on the real ABS sensor first.

https://youtu.be/HRvhzrsEQ28

21 minutes ago, Towrigdually said:

37 intermittent systems control module timeout

CODE 37 - Intermittent Signal From Rear Sensor.

Edited January 8, 2019 by Chris O.

[Towrigdually]

Sensor come back good, fluke beeps at me. So I guess now is time to play the follow the wire game.

[Chris O.]

Set the multimeter at the ohms (symbol Ω), look for (1600Ω - 2300Ω).

[Towrigdually]

I used ohms at first, then switched to see if I got the beep

[Mopar1973Man]

I went step farther and made a paper clip jumper. Plugged it in the sensor plug and ohmed the circuit from the ABS module. Should be less than 1 ohm.

[Dieselfuture]

9 hours ago, Towrigdually said:

I used ohms at first, then switched to see if I got the beep

To me it looks like your rear abs sensor is bad or a weak connection on prongs, need to be above 1600 and below 2300

 

[Towrigdually]

Tonight I'll bring home my fluke from work, it's I. Better shape than my home one, and certified so maybe I'll get a better read. Will test the sensor, sensor pigtail, and CAB connection tomorrow again using the paper clip method. I'll post back results. 

[Towrigdually]

tested everything out tonight using the work fluke, used the alligator clips on the rear sensor, rear connection, and used the paper clip method on the CAB connector. All reading came out the same. 

I think it's time to Chase wires, I have a feeling my issue is behind the fuel tank so I'll be putting it on hold till I run the tank down more. Then the search begins.

[01_Cummins_4x4]

On my 99 Cummins RWAL brakes only, the ABS and brake lights would come on almost every time I started the pickup and drove it. There were a couple times that it didn't come on for a day. My cruise control would come on, but it wouldn't always set when I pushed the set button. 

 

This evening I got underneath the pickup and noticed that the wiring sheath was broken and the "white" wire had an exposed spot due to it rubbing on the rear sway bar connector link behind the gas tank. I just repaired that wire and will test it out on my drive to work in the morning.