2005 BMW 318i CANBUS problem

Darren Fraser · Post by **Darren Fraser** » Fri Dec 24, 2021 6:09 pm

Hi all
One would think I had nothing better to do on Christmas Eve than post up a problem? Well you're right. Its just my wife and I here in Zambia and she is ill in bed at the moment trying to sleep off a tummy bug!

Anyway, Im fairly new at CAN diagnostics and Im hoping someone could help me decipher a problem Im having with this vehicle which has a crank no start condition, no communication with the DME and the MIL light does not come on when you turn the key on. (It has come on about four times in about 300 key cycles and only stayed on for a few seconds)

Im going to try and post up the psdata file together with a Word document that highlights my concerns.

liviu2004 · Post by **liviu2004** » Fri Dec 24, 2021 7:34 pm

2MS for canbus scoping? Sounds low to me. Up to 6-7 at least. There’s nothing wrong in that capture.

Darren Fraser · Post by **Darren Fraser** » Sat Dec 25, 2021 4:23 am

I agree, there is nothing wrong with this capture. However, all three captures are from the same buffer Liviu.

Did you look at the word document that has all three together with notes?

snap4749 · Post by **snap4749** » Sat Dec 25, 2021 3:57 pm

I would be getting a a wiring diagram for engine ecu and load test power & ground for engine ecu , another measurement you can do and it’s non intrusive by checking 5V ref on few sensor such cam& crank position sensor and see what voltage you have .

picowight · Post by **picowight** » Sat Dec 25, 2021 7:04 pm

Where did you take the sample from and in what condition. That looks like a module(s) pinging the network and getting no comms (or possibly your scan tool if it's connected). From the short sample it does not look like active communication.
Have you checked all power and grounds at the DME inc. any "wake up" wires

Darren Fraser · Post by **Darren Fraser** » Sun Dec 26, 2021 6:06 am

This capture was taken from the twisted pair at the DME, KOEO no scanner connected. I don't have a schematic for this vehicle but I have since discovered that the 16 pin connector only has two grounds (pin 4&5), power (pin 16), and one K line on pin 7.

I did manage to get a DME pinout for this vehicle and verified that the powers and grounds at the DME are good.

ronw38 · Post by **ronw38** » Sun Dec 26, 2021 9:01 am

Check the 5v reference circuit is not pulled to ground; often a cause of no mil lamp display and loss off coms Cheers Ron W

Darren Fraser · Post by **Darren Fraser** » Sun Dec 26, 2021 9:44 am

Thanks Ron. I'll look into that. Our shop re opens on 3/1/22.

PicoScopes
& kits

For vehicle manufacturers

EV kits and
accessories

Noise, Vibration and Balancing

Milliohm tester

Pressure sensors

Current clamps

Breakout
leads/boxes

Accessories

Automotive Forum