CAN BUS AND ELECTRICAL GRIMLINS

[apache64]

I am not one to normally post problems, due to i have not found many things that have not already been discussed. I have 2002 ram 2500 auto, 4x4, 24v, sport that has some major things going on with the modules, and can bus signal. I am getting readings from +3.5-4 volts -3.5-4volts. ref should be 5 volts overall limit. The injection pump has been tested standalone( cummins module) we have scoped the obd2 port on canbus+ and can bus-. the ecm has been disconnected to verify a change in signal limits( no change), and we are still having problems with out of limits voltage readings. More info... It had a tst powermax 3 stacked with a ts mvp tuner. The truck has been returned to stock to diagnose. If any of you guys have any input, I would be most thankful for any knowledge in this area. 

 

Thanks!

[Mopar1973Man]

I typically remove all modules (ABS, Air bag, central timer, etc.) then any tuner remove them as well. You should have only the PCM and ECM hooked up and check again. 

[Me78569]

Canbus wires don't go into the OBD plug, only SCI and CCD.

 

What pins in the OBD were you scoping?

[apache64]

i probed pin 6, and pin 14. 

 

[Mopar1973Man]

 

[Me78569]

So you are talking to the SCI bus on the PCM by probing those wires.

 

What issues are you having exactly?

[apache64]

I am loosing communication with the modules at random.  Transmission looses lockup-overdrive. canbus is over 3 volts positive, and 3volts negative on the the lab scope. Before I REALIZED that ccd was acting as canbus for the network( thanks Mike).

 

2 hours ago, Me78569 said:

So you are talking to the SCI bus on the PCM by probing those wires.

 

What issues are you having exactly?

I am currently plugging into pins 3, and 11 for ccd voltage.

 

[Mopar1973Man]

What is the voltage at rest? Have you unplugged all the other modules and checked and see if the problem goes away? I've seen some of the problems stem from a bad module (ABS, AirBag, Stereo, overhead, etc). I've also seen problems come from bad ECM or PCM too. So if you disconnect everything but the ECM and PCM and it still exist then drop the ECM and check voltage again. Basically start from rock bottom and work your way back up till you find the module screwing up the network.

[Chris O.]

When testing the CCD bus wires (pin 3 and 11) when probed with pin 5(or chassis ground) must have 2.5 volts each, at KOEO(Key On Engine Off).

If you don't get 2.5 volts at the CCD bus wires, check pin terminal connectors going to the following CCD modules:
 central timer, radio, instrument cluster, air bag, ABS, overhead console.

 

You can also monitor pin 3/11 with battery disconnected and expect to get 60 ohms* there.
 *Note: 120 ohm termination resistor
 While at least one termination resistor is required for the system to operate, most Chrysler systems use two. 
The second termination resistor serves as a backup.
If not, disconnect the CCD modules one at a time until ohmmeter reading returns to normal.

[apache64]

I am currently getting 2.45 volts on pin 3, and 11 grounding to pin 5(ground). I also have 60k ohms with batts disconnected. i m still having an interuption in the ccd thats causing to me to loose communication randomly.

[Chris O.]

It all appears to be correct as the voltage and termination resistor.
I don't see any issues here it's probably one of the connectors maybe loose.

Check the connectors and chassis ground on PCM, also check the connectors on instrument cluster Gage.
I would also check the big connector with the white plastic and a bolt in the middle of it above the brake pedal close to the fuse panels.

Don't forget to disconnect the batteries before you mess with the connectors.

Edited October 28, 2016 by Chris O.