2019 Toyota Highlander Charging Issue

I recently had 2019 Toyota Highlander (2GR-FKS) in the shop with an intermittent charging issue. It had almost 250k miles and had been in the shop a couple weeks prior because the generator locked up and basically imploded. Another tech replaced it with an aftermarket unit and it was towed back to the shop a few days later with a vague customer complaint about the “all of the lights on the dash coming on” and the car stalling. The vehicle started right up for me and I went through my usual process - data pids all looked great, voltage at the battery was around 14V at idle, voltage drop was normal on the B+ and ground side, etc…

I wasn’t able to duplicate the fault until I drove this for 35 miles!

Since TIS doesn’t give an example waveform of what I should be seeing on the LIN line from the generator, I was hoping someone on this forum might be able to explain what I’m seeing on the scope.

Channel A is on the LIN line at the generator and Channel B is on the battery current sensor

REPLACE WITH OEM UNIT AND GO FOR A DRIVE

I did and it fixed the issue. Just trying to dig a little deeper since Toyota doesn’t give any info on this LIN line. I wasn’t able to get a known good capture but I’ll try to get one on another vehicle this week

I think what you're seeing on the scope actually IS a known good. As far as the LIN is concerned, anyway.

I borrowed this from the Pico Auto library:

www.picoauto.com/library/case-studies/li...ntrolled-alternators

 

The waveform you posted has all the attributes and voltages that I'd look for in a correct LIN message. The master sent the header, and a slave responded. You don't know which slave responded, necessarily. But that waveform by itself looks good to me. It may be that the aftermarket alternator you were testing had an internal fault that didn't impact the LIN performance.

There are a couple obvious LIN issues you can keep an eye out for in the future. One is a missing response from a Slave. You'll see the master sending the header, but no answer from a slave. The frames with missing responses will stand out like a sore thumb compared to a complete frame. You could simulate this by disconnecting the battery current sensor on a known good vehicle.

Another is a LIN slave with excessive circuit resistance between the master and slave. You'll see the response pull down, but only down to 6.0V instead of 0V. 

If you do get around to looking at other known good examples, maybe take the network decoding feature of Pico 7 for a spin! I've always been impressed with the Pico decoding functionality.

Thank you! This is great information. I’ll definitely start messing around with the network decoding feature when I have the chance

Tyler, if there was a resistive problem in the wiring between the master and a slave, let's say a corroded wire, and you were to probe at the slave, the waveform would look all funny, right?

But would then probing at the master show a good LIN signal? Is that how it would work? I've never come across an issue like that, but it would help isolate a master/slave issue if at the master the signal on that wire was good, but at the slace connector it were to be odd looking.

Farseer wrote:

Tyler, if there was a resistive problem in the wiring between the master and a slave, let's say a corroded wire, and you were to probe at the slave, the waveform would look all funny, right?

But would then probing at the master show a good LIN signal? Is that how it would work? I've never come across an issue like that, but it would help isolate a master/slave issue if at the master the signal on that wire was good, but at the slace connector it were to be odd looking.

When probing at the master or the slave, the waveform would look noticeably wrong.

I couldn't dig up any of my known bad waveforms off hand. BUT while looking for some I ran across this awesome MVWautotechniek.nl article. It's got perfect examples and known bad waveforms with resistance added to the LIN:

www.mvwautotechniek.nl/en/lin-bus-diagnosis/