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CAN bus expert - disconnecting devices and bus termination


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Is there an expert here on the 05 LGT CAN-bus? Specifically, what is the effect on the other systems on the bus if one system is removed, and does this CAN have physical termination requirements to keep it electrically balanced?

 

From the vacation pix it looks like in '05 the CAN could have had:

 

-ECM

-Body Integrated Unit

-ABS

-VDC

-Steering Angle Sensor

-TCU

 

However, since my 05 is a manual Legacy, I think I only have:

 

-ECM

-Body Integrated Unit

-ABS

 

My goal is the removal of the ABS from the CAN without affecting the operation of the Body Integrated Unit and, to some degree, the ECM. I can go into Romraider and eliminate the limits and CEL's from a missing ABS, just want to see if anyone knows if there will be any other effects to the CAN side of the system, which I know very little about.

 

Thanks!

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you can remove just the abs module from the network without affecting the other modules on the network, but you may have to do some sort of a terminating resistor in the harness where the abs module would be. I cant be anymore specific than that, sorry.
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You can just take out whatever device you like.

 

The only one that cannot be removed SHOULD be the Body control module or if this car has a Canbus module. Most of the time it's part of the BCM.

 

Just remove whatever device. You will get error codes but it will not have any effect on other device.

10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned.

 

SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC.

Best 0-60: 4.651 by AP

1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission.

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The termination resistor is part of a network.

 

But the network is still looking to communicate with all the parts . If one of the parts doesn't reply it will set errors .

 

As far as I know there is no way of removing a part of the system.

 

If you just want to get rid of abs you can hydraulically bypass it and just leave it sit there.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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Yes if a device doesn't communicate you will get a lack of communication error for the given device but it will not crash or render the network inoperable.

 

I have never heard of the 120ohm resistor. I'd be skeptical of putting a resistor across the pair unless it was a very high resistance.

 

It may be to keep foreign noise from entering the network at the opening you made....but I am not sure.

10' CTS-V, A6, Airraid, 2.4 upper, ID850's, self tuned.

 

SOLD:06' LGT Wagon. BNR16G, Catless UP, DOWN, Hexmods VB, Hexmods diff bushings, BIG TMIC.

Best 0-60: 4.651 by AP

1/4= 13.678@100.73 mph, 1.945 60', Automatic transmission.

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If he doesn't want abs on the network it will just throw a communication code for the abs module.

 

As frank-ster posted he could just bypass and keep the module plugged in.

 

I guess to get a better understanding of what the op wants he will need to clarify what they plan on doing.

 

BMWs use terminating resisitors on the dlc itself.

 

If you measure the resistance of pins 8 and 14, on the dlc you will get 120 ohms, which is the resistance of all the modules on the network. The terminating resistor would be less than 120 ohm if its needed.

 

Sent from my XT907 using Tapatalk

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the termination resistors are actually not necessary .

 

the ecm wont care if you disconnected it .. or disconnected it and put a resistor .

 

either way you will get error HC on the odometer.

 

but you can still drive your car but only real thing is your cruise control wont work.

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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  • 8 months later...
Ok guys i know this is an old thread but maybe someone here can help me! I have an 05 lgt 5mt. My problem is as soon as key gets hot the coolant temp gauge pegs the top of the gauge reading max temp. Causes the car not to start in the cold and is messing with afr. So i changed the sensor multiple times. I just re wired everything between the sensor and ecu and have had no change. I get a p0117 code as a coolant temp sensor low input. So my next question is where exactly is the CAN bus located on my car? As well as the body integrated unit if anyone knows! Please someone help me i cannot find anything that is helping me!
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Ok so if your gauge is showing hot and your getting a code for open circuit that would tell me the problem is between ecm and temp sensor.

 

If the gauge or biu was acting up you would likly get a different code .

 

You say key is heating up? Is that a typo?

 

Have you tried unplugging the temp sensor when hot and shorting the two wires ? Or plugging into another sensor that is cold ?

 

As you say when the engine gets hot the gauge jumps up there must be something somewhere pulling and opening .

 

But try pluggingg in another sensor when its acting up and let me know of your findings

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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Ok so if your gauge is showing hot and your getting a code for open circuit that would tell me the problem is between ecm and temp sensor.

 

If the gauge or biu was acting up you would likly get a different code .

 

You say key is heating up? Is that a typo?

 

Have you tried unplugging the temp sensor when hot and shorting the two wires ? Or plugging into another sensor that is cold ?

 

As you say when the engine gets hot the gauge jumps up there must be something somewhere pulling and opening .

 

But try pluggingg in another sensor when its acting up and let me know of your findings

I meant like when you turn the key to the on position. i re wired everything between the sensor and ecu. And yes i did unplug the sensor before anything else and the gauge would still peg hot as soon as the key was in the on position which obviously kicks on the fans, i cant tell what else may be causing this issue unless its somewhere between the ECU and BIU, i found the BIU but cannot find the CAN. I followed the wires from the ecu going toward the BIU and fear the who dash may have to come out to see all the wiring to the CAN and then to the BIU. any insight from here would be great! If you have anymore questions about my symtoms that might seem helpful please ask away! Thank you

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the gauge pegs on any subaru when the sensor is unpluged ..

 

try shorting the two wires together.

 

i dont understand what you mean by you cant find the "can"

 

if you mean can communication is a type of communication.

 

do you have any other codes ?

 

the temp gauge has nothing to do with the biu , and if can comunication networ was down nothing would work. tach would not work speed would not work and you would have "ER HC " or others in the odometer

 

the coolant sensor uses i believe 5 volts from the throttle body and a few others and then goes back to the ecm. so you should be able to measure 5 volts at one of the pins.

 

do you ?

 

and try shorting the two pins together .

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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In order for us to help you, it would be easier for us if you could be a little more clear about what your doing. Be more clear about your questions, otherwise we'll grow tired of trying to decipher what you say and will lose interest in helping you.

 

Possible Causes

ECT sensor connector is damaged (check pins for damage, and for moisture)

ECT sensor signal circuit is shorted to ground

ECT sensor has failed

PCM has failed

 

DTC Setting condition

Key on or engine running; the PCM detected the Engine Coolant Temperature (ECT) sensor signal was more than 0.16v (a parameter of 300ºF). The purpose of this diagnostic is to detect a short circuit condition in the ECT sensor or its related circuit.

 

Sensor is two wires. One wire will be 5v supply to the sensor. The other will be the signal wire to the pcm, it will be real close to zero if its failed and causing the gauge to read hot. Key on engine off, this wire should have 1.0-1.4v.

 

Why did you rewire it? Did you trace a short to ground? If not you should have left the circuit alone. The idea is to reduce the variables that could cause your code. Not create more.

 

Do you have access to a volt meter, and know how to use it? if so use the info provided above to test the sensor and let us know what you get.

 

Quick question, do you still have the stock up pipe with egt sensor?

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  • 1 month later...

HI guys,

 

I am currently working on sniffing my canbus (06 LGT spec B) in order to import ECU/ABS data into my telemetry acquisition system. I have successfully tapped into my can bus lines, and using an arduino/canbus shield have sniffed the network:

 

23 00 00 80 01 FA 00 00 FE

101 AB AB AA 00 00 00 00 00

40 00 A9 00 AA 00 38 38 04

41 37 02 1B 19 DD 08 CE 06

 

The next part I am facing is actually deciphering the ID's and data. Before I start, I am wondering if any of you may have already done this, or if you know of a resource you can point me to.

 

Thanks!

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HI guys,

 

I am currently working on sniffing my canbus (06 LGT spec B) in order to import ECU/ABS data into my telemetry acquisition system. I have successfully tapped into my can bus lines, and using an arduino/canbus shield have sniffed the network:

 

23 00 00 80 01 FA 00 00 FE

101 AB AB AA 00 00 00 00 00

40 00 A9 00 AA 00 38 38 04

41 37 02 1B 19 DD 08 CE 06

 

The next part I am facing is actually deciphering the ID's and data. Before I start, I am wondering if any of you may have already done this, or if you know of a resource you can point me to.

 

Thanks!

 

what data are you looking for ?

 

using rom raider and tatrix cable many things can be data logged. with out speacial anything, also blue tooth to a android phone using the torq app or some of the others.

 

with megasquirt that i am using i data log to a android tablet and it even records gps data and uses the optional megasquirt g meters and or the tablet / phone g meters

 

as for resources , megasquirt is also working at similar things , ie: controlling a can dashboard

 

so perhaps check with those guys on the starting points ,

920441481_Screenshot_2015-04-04-00-13-211.thumb.jpg.332465705a26d98c27f69197e26d5253.jpg

Now that's thinking out of the boxer!:lol:

fyi all 05 + legacy's have built in code reader

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what data are you looking for ?

 

frank_ster; I hope to get the following data off the bus:

 

* RPM

* Speed

* Throttle Position

* Coolant Temp

* Gear (if possible, this may be broken now that I have switched to a 6 speed)

* Brake

 

I've been looking through the romraider code, hoping to find where/how they are pulling the data and converting it to usable values, but not too much luck thus far. I've also hit up another guy working on a similar project from a different angle, he is trying to get a lgt cluster to respond to can codes from a similar arduino.

 

Anyway, thus far all of the ID's I am seeing in my canbus dumps appear to be OBDII PID (as defined here: http://en.wikipedia.org/wiki/OBD-II_PIDs). I'll know more as soon as I replace my downpipe and actually go take the car for a drive.

 

I'll hunker down more this week and see if I can continue peeling this onion. I've posted on this thread, since it seemed to have the right guys. I can either continue posting here, or start a new thread.

 

Thanks!

Ryan

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Im just curious why you are not just using rom raider to datalog ?

 

I'm going for a more elegant, complete system. As my purpose here is to capture telemetry data at the track, not tuning.

 

I am using a race capture pro to pull in all of my aftermarket sensor data. In addition, I have it connected up to an arduino to handle camera control. Previously I have been using the system in addition to my cobb AP (for logging). However, merging the two data streams is difficult and time consuming, not to mention, having to get more then one logging system going before my lap.

 

My RCP system is completely integrated into my lgt's dash, using jdm switches. This is a much more clean approach then logging with an AP or a laptop. This video shows a session from last season, this is the RCP + the AP. Utilizing canbus, my hope is to eliminate the need for logging with the AP all together.

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You need to contact Sgt gator. He has the old scca legacy wagon, and he logs telemetry.

 

Boxkita used to track his often, these two guys will be your best bet for answers

 

You should also create a new thread so you don't hijack this thread.

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