Can Bus Vs Older Electrical Sytems

[LazyDog]

I recently started leaning about the newer Can Bus electrical systems and wonder if there is a quick way to find out if a particular car has Can Bus.

I know that experience and Google are your friends in most cases besides experience. Some of the stuff that we could do w/ older electrical systems do not apply w/ Can Bus stuff.

This guy has a very good explanation of a Can Bus system.

 

[2EHA]

pretty much any car made in the last 15 years uses CAN for something

 

[atikovi]

I need to get me a BOB.

 

[Kira]

What's a BOB?

OK basic info. Good to see but the video did not need to be 16 minutes long.

 

[Spectre694]

If there is an OBD2 port then it almost certainly has some sort of can bus in it.

Some cars have more than one or additional proprietary networks as well.

 

[MrHorspwer]

If there is an OBD2 port then it almost certainly has some sort of can bus in it.

This is not true.

Simply having a J1962 doesn't mean the vehicle has a CAN bus.

The J1962 connector was rolled out along with OBD-II in 1996. In America, vehicles weren't required to use ISO 15765 until 2008.

From 1996-2008, communication protocols were all over the place. Some European manufacturers were using CAN (not many though). Almost all Asian manufacturers used Keyword (KWP2000). American automakers used proprietary implementations of J1850 (Chrysler = PCI, Ford = SCP, GM = Class II). UART was even used for a long time (ISO 9141).

There are many communication protocols that have been used in vehicles. CAN is only one of them. There are a number of other communication networks that could be on the vehicle, communicating through the J1962 OBD-II port.

Also, the days of diagnosing CAN at the J1962 shown in the video are largely over. Almost all manufacturers now use a control module that gates messages between the J1962 and the rest of the vehicle. That is, there is not a physical circuit connection between the circuits terminated at the J1962 and the rest of the vehicle. Checking voltage and resistance at the J1962 is only good for testing between the J1962 and whatever module is gating the messages, not all the controllers on the vehicle.

 

[Spectre694]

This is not true.

Simply having a J1962 doesn't mean the vehicle has a CAN bus.

The J1962 connector was rolled out along with OBD-II in 1996. In America, vehicles weren't required to use ISO 15765 until 2008.

From 1996-2008, communication protocols were all over the place. Some European manufacturers were using CAN (not many though). Almost all Asian manufacturers used Keyword (KWP2000). American automakers used proprietary implementations of J1850 (Chrysler = PCI, Ford = SCP, GM = Class II). UART was even used for a long time (ISO 9141).

There are many communication protocols that have been used in vehicles. CAN is only one of them. There are a number of other communication networks that could be on the vehicle, communicating through the J1962 OBD-II port.

Also, the days of diagnosing CAN at the J1962 shown in the video are largely over. Almost all manufacturers now use a control module that gates messages between the J1962 and the rest of the vehicle. That is, there is not a physical circuit connection between the circuits terminated at the J1962 and the rest of the vehicle. Checking voltage and resistance at the J1962 is only good for testing between the J1962 and whatever module is gating the messages, not all the controllers on the vehicle.

You're correct looking back I wasn't very clear in my post and I suppose didn't add much to the thread.

I was more referring to the general controller networks rather than the specific CAN bus. At least where I work all different controller networks are called can bus regardless of their actual name. I don't know anything about OBD1 at all.

 

[mightymousetech]

If there is an OBD2 port then it almost certainly has some sort of can bus in it.

Some cars have more than one or additional proprietary networks as well.

More than one? Eesh.
CAN-BUS is not new, it has been around for at least 15 years.
Most of the cars I work on have 5-6 different networks, plus all the various LIN-BUS for things like interior lighting, HVAC motors etc. CAN-BUS is one of the simplest.

 

[2EHA]

SCP and the other 1850 protocols are CAN type but they’re not quite as versatile and eventually deprecated.


ZF transmissions had CAN controllers talking with the PCM by the late 90s. i think ford stayed with an integrated pcm/tcm on cars with the 5R family just to avoid paying royalties to bosch

 

[LazyDog]

More than one? Eesh.
CAN-BUS is not new, it has been around for at least 15 years.
Most of the cars I work on have 5-6 different networks, plus all the various LIN-BUS for things like interior lighting, HVAC motors etc. CAN-BUS is one of the simplest.

Do you have video handy that explains the newer systems LIN-BUS that you mention.

 

[mightymousetech]

Do you have video handy that explains the newer systems LIN-BUS that you mention.

No videos, I basically learned them all from factory training.

Here is a short description of some of the various BUS. These are from an older E90, so much more complex now with the introduction of Ethernet and Flexray BUS networks.

LIN is probably the easiest to diagnose. When one item on the BUS goes down, the entire BUS is down. You can simply unplug things on the network one at a time and see if the rest come back. Classic example of this is on BMW E90 where the alternator, oil level sensor, water pump and thermostat are on a single LIN. Or on the newer cars, the interior LED lighting has two LIN BUS, one on drivers side, one on passenger. Leave something disconnected and the whole side will be down.

 

[sloinker]

Basically each manufacturer uses their own protocol except for what the fed requires to be at the OBDII connector for emission purposes iirc. The days of just changing a part and hoping for a fix are largely going away as each system may only recognize a specific address on a network and not recognize a replacement, like replacing an ABS controller on a RAM pickup requires address intervention for it to be used. Like that on pretty much anything new nowadays it seems. Transmission, Engine, Central Covenience. SRS, HVAC etc etc etc....

 

[Tomioka]

The Toyota electric pallet jacks we use at work uses CAN-BUS communications between the onboard charger, motor, till handle, etc.. Even installing the wrong on board charger can brick them requiring reprogramming.

 

[LazyDog]

Thanks guys for all the replies, the new game is know what you are working on. Do the research before you dive into any work.

 

[Kira]

To MrHorspwer: Thanks for the meaty post.
However, the J1962 plug was used in early OBDl systems before 1996.
The one on my friend's 1989 K1500 was for ABS and one other diagnostic. He had an extremely limited code reader for these two tasks.

That truck (Silverado) had its computer at the rear of the glove box and extended into the engine compartment.
Also, the clutch hydraulic line snaked over the bell housing to the passenger's side making me think that maybe GM sold most of those gearboxes in the UK.

 

[MrHorspwer]

To MrHorspwer: Thanks for the meaty post.
However, the J1962 plug was used in early OBDl systems before 1996.
The one on my friend's 1989 K1500 was for ABS and one other diagnostic. He had an extremely limited code reader for these two tasks.

That truck (Silverado) had its computer at the rear of the glove box and extended into the engine compartment.
Also, the clutch hydraulic line snaked over the bell housing to the passenger's side making me think that maybe GM sold most of those gearboxes in the UK.

SAE first issued the J1962 standard in 1992. An '89 Chevy truck couldn't have a J1962: It hadn't been invented yet.

J1962_199206: Diagnostic Connector Equivalent to ISO/DIS 15031-3:December 14, 2001 - SAE International

This document supersedes SAE J1962 200204, and is technically equivalent to ISO/DIS 15031-3: December 14, 2001.This SAE Recommended Practice: a. Defines the functional requirements for the vehicle electrical/electronic diagnostic connector. These functional requirements are separated into two princ

www.sae.org

A Chevrolet from 1989 would have had an ALDL, which maybe looks like a J1962 if you aren't wearing your glasses. The most common implementation of the ALDL was rectangular and had 12 terminals, compared to the J1962, which is a trapezoid and has 16 terminals.

 

[Kira]

10-4
Now that you mention it my pal was primping the troubled '89 for sale. He ran out and bought the special reader in a huff.
I did get only a glance at it (though I was wearing my glasses)