I have been searching for a couple of months for information on were i can tap in and get a velocity measurement in the wiring of this truck.

I am testing an inertial navigation system and we are trying to integrate it into common vehicles and would like to start with our 2500.

For instance the bully dog PDA has a speed read-out were does it get that information from

any thoughts or help would be appreciated.

 

they use input and output speed sensors on the transmissions....would need to know what type of tranny is in it to tell you more

 

right I understand that and i believe its a 48re maybe way off there 4x4 5.9l. I was able to find a wiring schematic on dodgebodybuilder.com but im looking for more detail on the actual pin-out on the can bus port or even the obdcII code.

 

The speed sensor from the rear differential and the rear of the transmission send a signal to the ABS module. Then , the ABS module sends the info thru the bus to the instrument cluster that then deciphers it to a signal sent to the speedometer. Not easy to translate into leyman's terms. There is nothing I have been able to find as to what the signal is ( or supposed to be ) from sensor to ABS module or from ABS to instrument cluster. There really isn't a spec for that. Here is the pinout for the rear sensor and the ABS module.

MODULE-ANTI-LOCK BRAKES (AWAL) - 46 WAY CAV CIRCUIT FUNCTION
1 - -
2 A111 14DG/RD FUSED B(+)
3 D65 20WT/LG CAN C BUS (+)
4 - -
5 - -
6 B29 20DG/WT BRAKE SWITCH NO. 1 SIGNAL
7 - -
8 - -
9 - -
10 - -
11 - -
12 B9 20DG/LG LEFT FRONT WHEEL SPEED SENSOR (+)
13 B8 20DG/TN LEFT FRONT WHEEL SPEED SENSOR (-)
14 - -
15 - -
16 Z107 14BK/DG GROUND
17 - -
18 D64 20WT/LB CAN C BUS (-)
19 - -
20 - -
21 K75 20DB/OR (SRT) VEHICLE SPEED SIGNAL NO. 1
22 - -
23 - -
24 - -
25 - -
26 B7 20DG/VT RIGHT FRONT WHEEL SPEED SENSOR (+)
27 B6 20DG/WT RIGHT FRONT WHEEL SPEED SENSOR (-)
28 - -
29 - -
30 - -
31 A107 12TN/RD FUSED B(+)
32 F202 20PK/GY FUSED IGNITION SWITCH OUTPUT (RUN-START)
33 - -
34 - -
35 - -
36 - -
37 - -
38 - -
39 - -
40 - -
41 B22 20DG/YL REAR WHEEL SPEED SENSOR (-)
42 B222 20DG/WT REAR WHEEL SPEED SENSOR (+)
43 - -
44 - -
45 Z127 12BK/DG GROUND
46 - -



OPERATION
The speedometer gives an indication to the vehicle operator of the vehicle road speed. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Controller Area Network (CAN) data bus.

The speedometer is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or START positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the OFF position. The instrument cluster circuitry controls the gauge needle position and provides the following features:

Vehicle Speed Message - Each time the cluster receives an electronic vehicle speed message from the PCM it will calculate the correct vehicle speed reading and position the gauge needle at that relative speed position on the gauge scale. The cluster will receive a new message and reposition the gauge pointer accordingly about every 88 milliseconds. The gauge needle will continually be positioned at the relative vehicle speed position on the gauge scale until the vehicle stops moving, or until the ignition switch is turned to the OFF position, whichever occurs first.
Communication Error - If the cluster fails to receive a speed message, it will hold the gauge needle at the last indication for about three seconds, or until the ignition switch is turned to the OFF position, whichever occurs first. After three seconds, the gauge needle will return to the left end of the gauge scale.
Self Test - Each time the cluster is put through the self test, the speedometer needle will be swept to several calibration points on the gauge scale in a prescribed sequence in order to confirm the functionality of the gauge and the cluster control circuitry.
The PCM continually monitors the Vehicle Speed Sensor (VSS) or electronic wheel speed messages from the Controller Anti-lock Brake (CAB) to determine the vehicle road speed. The PCM then sends the proper vehicle speed messages to the instrument cluster, also known as the Cab Compartment Node (CCN). For further diagnosis of the speedometer or the instrument cluster circuitry that controls the gauge, (Refer to 08 - Electrical/8J - Instrument Cluster/Instrument Cluster - Diagnosis and Testing) .

For proper diagnosis of the VSS, the CAB, the PCM, the CCN, the CAN data bus or the electronic communication related to speedometer operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.

 

2 diff speed sensor types used depending on year,a resistive inductive or a hall effect.Any one sharp enough to work on the system should be able to figure it out.

Bob