What's your issue, BUS DOWN?
Usually the causes are the integrity of the wires and the modules connected to the BUS.
The integrity of a wire includes the continuity from end to end and the insulation between touching wires.
The continuity should be less than 10 ohms.
The insulation should be over 100 Kohms. (Resistance between any two wires in a harness, including B+ power and ground wires).
Each module has its own resistance/impedance.
A short/defective module can bring down a BUS.
According to FSM, AFAIK
, troubleshooting is done by isolation of a module, measuring resistance, check for short to B+, ground and other wire. Suggest to follow the steps from FSM. It's not that simple.
The CAN BUS is a comm network with two wires (can+/can-).
Usually it's a twisted pair of cable with grounded shield.
I think we can see what they are talking about by using a protocol analyzer. (It's an IT thing.)
You may see some signals with a voltmeter across the can+ and can-.
My problem is rather severe.
Heres my history:
I rebuilt the cummins after it went down. Got it back together and it was in theft mode. I took it to a dealership and they found all kinds of problems. Replaced the ECM AND the TIPM and still some issues. They found the overdrive solenoid in the tranny was busted up and fluid got in the connector and started shorting everything out (ECM and TIPM for sure it seems).
I still have all kinds of issues though. My cluster wasn't working. Only showed Miles, fuel level, and volts...nothign else worked. As well as, no OBD2.
I dont even get the "No bus" on the cluster. I just bought a new (used) cluster (exact same part number) and installed. My injectors are being sent back to check for issues under warranty so I can't start the truck...but I checked the cluster with just key on. It doesn't show my gear indicator so im assuming I still have issues.
And my OBD2 isn't working.
I've tried to follow the FSM as much as I can, but the problem is, they want you to use the OBD2 port with a scanner to try isolating things. Well, that does no good if there is NO COMMUNICATION at all at the OBD2.
Had this problem for a few weeks now. The truck will run and drive down the road (I have injector issues though, which im not so sure are injector problems or electrical problems).
So essentially, I have to back probe every single thing.
It seems to be that everything is actually working just as it should, it's just not talking to anything at all. My blinkers, headlights, brake lights, etc all work fine. Truck shifts fine I think.
So my goal is to 1) Check the integrity of every communication wire. 2) check all of my 5v supplies and grounds 3) try to see if I can actually see if the communication lines are actually talking. I assume the messages are extremely fast and I won't be able to read an exact voltage, but I think if I put my dvom on there and it goes crazy all over the place....it would be safe to assume that module is talking. If I just get a flat volt reading then I can assume that its not talking....does this sound correct? I'm just making it up as I go right now.
So far, I've been able to track down most all of the CAN wires and they all have continuity and all the connectors seem good.
Today I'm going to track down the other numbers that were in the picture I listed. the SCI receive/trasmit. I was able to track it down to the connector on the floorboard under the pedals (think they informally call it the 100pin connector). It then travels to the big connector on top of the firewall roughly right above the engine. the big square one.
I'm not sure what the SCI is, but will look into it as well.
If no issues are there, then I need to assume that all of my CAN wires are in good condition, and need to start looking at why they aren't talking....possibly looking for a lack of ground/5v, or maybe a single module being down and not talking nor letting other communication bypass it.