Can communication Issue

This is more informative then anything.
I have been dealing with a customers vehicle from another dealer which came in with can communication issues so lets get down to the details.


Vehicle: 2015 Tacoma double cab 4 cylinder w/o tow package
Odometer: 66,000
Has been in an accident in front left corner.
Engine bay recently power washer and inside detailed too much.
Vehicle was from another dealer and purchased at auction.
Vehicle was purchased by customer at other dealer and brought vehicle right back, that dealer was unable to figure it out so they sent it to us.
Arrived with skid and abs light on. Rpm and coolant gauges would fluctuate randomly. Intermittently No data list for abs module and intermittent communication to abs module.
Dtc's: U0073, U0123, U0124, U0126, C1421
_________________________________________________________________

C1421 was related directly to skid control ecu as an internal fault and vehicle was heavily power water under hood and detailer spray was used ( alot! ). I found water inside the abs module connector so clearly they over killed it and cause come damage.

The dealer decided they would replace the skid control ecu themselves. A few days later the vehicle returned and they stated it was doing the same thing.
Although rpm and coolant temp we no longer fluctuating and vehicle had a few new dtc's. P2759, P0412, B1655, U0124, B1821, U0073, U0123, P0453, P2433, B1653, U0126. So after looking into some of the codes i found that they installed the wrong actuator which was causing some codes and that again they power washed and detailed the car for the customer after being told we found water inside the connector. We told them they need to install the correct actuator and we can go from there.

Again a few days later they said they installed the correct one and stated they still had the lights on.
So back into it. Vehicle arrived with dtc's U0073, U0123, U0124, U0126 all pertaining to can bus off, yaw rate and steering angle sensor.

At this rate i knew we had a separate issue going on in the network or other ecu's. Taking a look at the waveform with the picoscope showed this very quickly. voltage spikes, packets were not mirrored and arking idle times. Taking a look at the repair manuals showed that it was not going to be much help with this vehicle.

- At this point i tested the terminating resistors, good at 62 ohms.
- Checked power and grounds to all ecus on the can bus. All good.
- Performed a resistance check of all wires on the can bus network all good.
- Disconnected ecu's one by one to see if waveform would improve, when disconnecting a branch connector the signal improved completely. But that disconnected about 5 ecu that were on that branch so i knew the problem was somewhere inside the vehicle.

At this point i was unsure if they fried other ecu's with all the cleaning they did. It looked like they tire shined the inside of the car with a paint gun and got into everything.

After disconnecting the steering sensor connector i found the signal improved slightly. So i wondered if it was an issue with the pins themselves on the connectors.

So i checked every pin at every can connector and to the ecus we were having issues with. Well what what do u know i ended up replaced over 6 pins because it was like a hot dog down a hallway. One pin at the abs module which gave me the abs data list back. both can high and low at the steering angle sensor and several the communication wires at the can bus branch connector.

But that got me thinking why the crazy voltage spikes on the picoscope? where was that voltage coming from?

Well those bad signals on the scope showing bad packets and voltage spikes ended up being those loose pins causing bad signal frequency's in the network which appeared to be voltage spikes.

_________________________________________________________________

I felt as though better info on communication issues like this to be out there because i was unable to find any info on bad can bus signals such as this and a procedure on how to start diagnosing. The repair manual was very little help and also anything online basically pertained to one ecu causing an issue. So if you have issues where abs is coming on and off randomly rpm flutter issues. No communication. Check your pins!! And do the proper checks.

 

With welding machines getting loose or bent pins is quite common

Very Good write up !!

 

Well Done..

 

So glad you posted about this. My 2013 just popped these exact codes. I suspected it would be a bad connector at a branch that took out those modules, and your post confirmed it. However I have no idea where these connectors and modules are located on the vehicle. Would you be able to tell me where to look? Does there exist a wiring diagram that shows the layout of the harness and the module's locations? Thanks.

 

its located near the driver side kick panel on the large wire loom. its hard to find because it is electrical taped over into the harness so i will have remove tape to find it. Its looks like regular connect with a black plug on it but inside the plug are a bunch of small pins.

 

Sorry it took me awhile to get the diagrams you need. But here they are, pics of where the branch connector is located and the pinout for it.
The branch connector is hidden though and covered up with electrical tape onto the large main harness located in the pic, so grab onto it and feel for a connector under the tape.
----
Start with checking the pin fit at the branch connector and the spiral cable those will most likely be the areas were u are having the issue.