mountainmanjoe

No, your vehicle has both an ATA and a TCM. There are various types of CAN bus with various numbers of termination resistors, depending on wire length etc. With high speed communication you have to start addressing things like reflections, impedance matching and power line effects.

https://en.wikipedia.org/wiki/CAN_bu...cal_properties

rockfishon

Based on my older scope analysis, I believe that I have a module that is corrupting the bus. Instead of randomly replacing modules, my goal is to capture the data of the offending module and gather the ID field of it. Then I will know what module is bad and replace it. I have seen others troubleshoot it by pulling fuses to the modules one at a time until the bus looks clean, but I am going to try this method first.

LCAC_Man

if you really believe you have a module issue you need to borrow a GM MDI / GDS tech tool, it will allow you to determine/test the health of each system. Your van is too new to use the older Tech2 which is pretty common at local service shops (I have one myself and they are invaluable but my van is an 06).

rockfishon

Thanks for the info LCAC_Man.

Just a quick update. The engine starts every time I try now, I can no longer make it fail. I did not do anything to fix it that I know of. For additional troubleshooting, I purchased a "CANable" CAN to USB adapter. I was able to configure the adapter and connect it to a Raspberry PI 3 and run Wireshark to capture raw CAN bus packets. I was specifically looking for packets with the "error" bit set in the CAN header which would represent bus errors. I captured packets for an extended period of time and did not see a single error. I guess I will have to wait till this problem reoccurs to troubleshoot further.

Till next time.......

rockfishon

Problem back. My vehicle is an RV so I went to use the vehicle last weekend for the first time since December and the same thing happened again. Turn key , dash goes dark and nothing happens, the engine does not turn over. Stop turning key and "SERVICE AIRBAG" is displayed and dash chimes 33 times. I then used the same method of getting it to start as before. Opened the drivers door and closed it. Waited for the mileage to disappear, turn the key to on, wait for 4 seconds and then start. It has started ever time after that. At least I think I have a work around and hoping it does not stick me on the road in some distant city.

huntster

Engine not turning over is NO CRANK, not No Start!

ChevyVanMan

Check your ground wire around starter location for being loose.
Thank you
Ken

dberladyn

I am getting this problem, but it's the positive cable on the battery. I just pop the hood, give it a very small turn... click click click... goes all the relays and she's back to life. I have to fix that sometime.

rockfishon

I now have completely different symptom. I think HUNTSTER jinxed me. The engine now turns over but will not start. Nothing I do seems to get it to start. At least this is a hard failure and so I should be able to figure out the cause. Going to start with fuel pressure test and see if it has spark. No codes are stored.

I disconnected the battery and disconnected/reconnected the BCM. Reconnected the battery. Still turns over but does not start. I pulled the cowling off the engine to see where to measure fuel pressure. It does not look like there is a valve on the rail to read the pressure.

Any ideas on how to read the fuel pressure?

mountainmanjoe

what engine?