No crank, no communication with CEM

Joelsplace · Post by **Joelsplace** » 19 Jun 2021, 06:03

2004 V70 that I'm trying to help a friend out with. I'm using a Vident scanner that is supposed to communicate with all the modules but I get a communication failure no matter what module I try to read.
The problem with the vehicle is no crank. It shows a "severe" air bag problem on the dash. The transmission indicator shows the proper shifter position. If I jump the starter relay it cranks but doesn't start.
I'm thinking that there is something wrong with the computer system since I can't communicate with any of the modules.
It is looking like a CEM high speed CAN bus failure. ?
Help!

MDK · Post by **MDK** » 19 Jun 2021, 08:25

So, I can tell you from what I've seen

MDK · Post by **MDK** » 19 Jun 2021, 08:25

So, I can tell you from what I've seen. There is a man named Bernie Thompson. He has a YouTube channel called ATS .. automotive test solutions.. who uses an ociliscope to fix these types of problems. You should check that out. I think that's probably what you need to look at this point. MDK

Joelsplace · Post by **Joelsplace** » 19 Jun 2021, 09:36

I'll check that out.
Thanks!

Joelsplace · Post by **Joelsplace** » 19 Jun 2021, 14:23

I connected my scope and no signals on bus. I'm guessing the CEM is responsible for that? None of his videos I've watched so far tell you how to tell what device is responsible for bus arbitration and power.

MDK · Post by **MDK** » 19 Jun 2021, 19:38

You should check out the Dodge Ram 1500 with no start communications failure. He goes way above what I can do. His machine and the system he uses is awesome. He basically starts in plugging modules until he get a can bus signal on the scope and goes ..ah that module is keeping the high speed from communicating..step by step by step.. Joel.. like I said beyond my capabilities.

jking4020 · Post by **jking4020** » 22 Jun 2021, 18:02

Remember sometimes with electronic failures it could be something as simple as a bad ground. My mom's 99 V70 XC had a no start problem and we found a bad ground and it started right up. These cars can suck but we love them so.