08 xc90 lost canbus? Topic is solved

2000c70hpt · Post by **2000c70hpt** » 04 Jun 2020, 15:29

Ok so here’s what’s going on. Started loosing fuel pressure after fixing a stuck float on the pump side of the tank. Got a code for the fuel rail pressure sensor. Changed it out ran great for a few days. Symptoms came back, so I figured what the hell. Let’s change the pem too. Yay fuel pressure normal runs great! Now all of a sudden I have no communication with the ecm, tcm, bcm, and sas modules. I have no broken wires, while doing a basic canbus test 2.7v on the high side, 2.3v to the low side and 60ohms while the vehicle is in pos 2. Now as soon as I start the car, it idles and runs all day perfectly as long as I am moving. If I start it and let idle for a few minutes, the gear indicator goes from P to - in the display. This tells me bad tcm, as the codes in vida correlate that. But it’s also saying lost comm with ecm as well. So I put a used ecm in (not expecting to be able to start it cause of wrong software) and I still have no communication with the above modules. Anyone got any ideas?

The is an 08 xc90 3.2l non turbo, fwd.

2000c70hpt · Post by **2000c70hpt** » 04 Jun 2020, 15:40

Forgot to mention. I do have vida dice

Post by **yagger** » 04 Jun 2020, 16:16

In ideal case, you have to use oscilloscope for check signal on CAN bus.
But, you can start from:
check top connectors on CEM for water damages,
disconnect DEM connector for confirm DEM is ok or no.

2000c70hpt · Post by **2000c70hpt** » 04 Jun 2020, 18:04

No water on the cem as I’ve already had it out looking for corrosion and popped surface mount components. Dem? Do you mean the dim? Driver info module? Checked it. The only oddity I’ve noticed was a 10 mile discrepancy between the dim and vida.

Post by **yagger** » 04 Jun 2020, 19:49

DEM - Differential Electronic Module

2000c70hpt · Post by **2000c70hpt** » 05 Jun 2020, 05:05

My vehicle is not equipped with that module. It's only front wheel
On a side note i put the original pem back in since my issues I think started after the change

2000c70hpt · Post by **2000c70hpt** » 05 Jun 2020, 16:08

Well a little update. I reinstalled the original pem and regained communication with the rest of the modules. Though I’m have fuel pressure issues again. From cold start it runs great. This morning I even let it idle for 30 minutes and then took it for a drive and ran great. After sitting for. 4 hours fuel pressure issues started again, and check engine light came on.

Post by **yagger** » 05 Jun 2020, 16:16

Do you have a list of errors?

2000c70hpt · Post by **2000c70hpt** » 06 Jun 2020, 06:02

Still lost tcm and a code for the little bulb in the antenna

Edit: After serious testing today I regained comm with the car. Though the tcm had to be disconnected. All wires check out, fuses good, I’m at a loss. It’s really starting to look like a tcm. Does anyone know if a used one with a software update will work? Or do I have to use a new one.

Post by **yagger** » 06 Jun 2020, 13:28

Still lost tcm

Can you do screenshot of errors and Network tab also?