2013 FORD F150 5.OL ABS NO COMM, CAN BUS

I have a question about CAN communication. I have this 2013 Ford F150 with an ABS module not communication. I have tested all powers and grounds and the all check out (tested with a headlight the draws 4 amps current). The ABS module has two separate set of CAN wires, one set goes to the main CAN BUS and the second goes specifically to the SRS module for the yaw rate.

First image is from the PCM (the ABS module has the same pattern, I forgot to save the pattern to the ABS module.) I went to the PCM to get a known good signal.





Second image is at the ABS module back probed to the set of CAN wires going to the SRS module.




There is a distinct difference in the signal with the downward voltage trace. When I disconnect the connector to the ABS module the signal will look like the first image.

I haven't had too much experience with know bad CAN signals. So my thinking would be that the ABS module has a short to ground causing the downward voltage trace. I am wondering if my conclusion is sound or is there something else going on.

Oh, btw. this is a salvaged truck that has been rebuilt. The dealer that brought it to me has told me that he has replaced the ABS module twice with no luck in fixing the vehicle. I did see some insulation on the can wires damaged to the point of showing copper but there were no broken strands. I repaired the insulation with some liquid electrical tape temporarily.

Thanks in advance for your input

Disconnecting the module which fixes the signal seems to condem it in my eyes.
Are the abs and srs modules the only modules on this data line? If so both need a terminating resistor don't they? Have you done a resistance measurement? Both across the lines and from either line to ground?
I'm no more experienced than you sorry. I'm just trying to help. It does look like it's being pulled down though doesn't it.

I dont have a wiring manual, but is this measured between the ABS module and the airbag ecu? Are there any fault codes stored? How is the ground of the chassis to the battery negative terminal?

Please post a longer recording (about 2 seconds) to see if the message has a OK bit or a fault flag

This is a good data signal



Check the ground of the ABS-controller. If that is ok, and the signal is pulled down, then it seems the transiver has a fault to ground and needs to be replaced. This is a non serviceable part, and that will mean that the ABS module needs replacment.

Here is a video capture of the waveform. I didn't notice it before but there is no acknowledgement signal in the trace.



There are two sets of CAN wires on this module, the one with the bad signal is dedicated ABS to AIR BAG Module to transmit for the yaw signal from what the diagram says. The other CAN wires go to the main CAN system.

I have not checked the CAN wires from the ABS to SRS modules for shorts to ground or each other, the SRS module lives under the center console. When I get a chance I will have to remove the console to test the wires.

I had originally condemned the ABS Module. Then I informed that the used car lot had previously replace module twice, with salvage yard parts of course. Now I am second guessing my diag.