2004 V70 Will not start, possible issue with CAN bus

jman294 · Post by **jman294** » 04 Feb 2019, 10:08

Recently acquired this car, and it will not start. We knew it was probably an electrical issue from the previous owner, not mechanical. VIDA

shows errors with ECM communication, but with the CAN bus. We have checked ground points, a few other things, but kind of stuck on where to go next. Any ideas? Sorry if this is not enoigh information, new to Volvo repairs.

Thanks

Post by **RickHaleParker** » 04 Feb 2019, 12:54

Pull the CEM and clean the electrical connectors with MAF cleaner then reconnect.

If that does not work, one at a time disconnect the BCM, TCM, ECM.
See if doing so re establishes communication with the other two control modules. One of the three may be defective pulling down a common CAN bus line.

jman294 · Post by **jman294** » 10 Feb 2019, 12:05

I pulled the CEM and haven't cleaned the pins yet, but they look fine. I haven't been able to pull the computers out because I don't have the tool yet, but will soon.

Thanks.

Post by **RickHaleParker** » 10 Feb 2019, 12:59

Keep in mind, even a thin layer of oxidation can cause problems.

jman294 · Post by **jman294** » 15 Feb 2019, 17:57

Did some checking today.

We removed BCM, checked VIDA and nothing much changed. We removed both computers one at a time and then added one back in and nothing changed. At the end of the day, with the TCM and BCM removed VIDA displayed these errors.

A lot of the errors seem to do with relays, but we did check them.
We cleaned the pins on the CEM as well as both computers with MAF cleaner.

Once again, we are very new to VIDA and Volvo repairs in general. Appreciate any help you can give, and apologize if we are perhaps not providing the right information.

Post by **RickHaleParker** » 15 Feb 2019, 18:29

Click on the Diagnostics Trouble codes (DTC), your get a description of what can cause them. Look for a common factor.

Post by **precopster** » 16 Feb 2019, 06:08

The TCM, BCM and ECM are not reporting to the Network. They are possibly all lacking power or grounds.

I'm not sure if ECM gets power through the TCM.

Check the red leads going from the battery area strip fuse. Follow those red leads until they come to a pair of connectors in the rear left corner of the car and check those connectors thoroughly for corrosion.

The pic provided is from an XC90 but I believe the same connectors are used on the XC70s

Place all modules back in, go to Network and see if you have identity on all modules by clicking each one

jman294 · Post by **jman294** » 16 Feb 2019, 08:09

We could not find that connector in the picture. We checked in the rear cargo area all around. The leads under the hood in the front looked fine, however.

Post by **chrism** » 16 Feb 2019, 08:58

jman294 wrote: ↑15 Feb 2019, 17:57
We removed both computers one at a time and then added one back in and nothing changed. At the end of the day, with the TCM and BCM removed VIDA displayed these errors.

Are you saying that you ran VIDA diagnostics while one or more components were removed? I don't possess a VIDA/DICE setup so I'm no expert. But logic would tell me that if you don't have ALL of the pieces in place when scanning the system that you would likely get ALL KINDS of crazy results, some possibly WAY misleading.