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Subaru Airbag ECU data...

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The airbag module isn't happy in my  MY05 Liberty 3.0rb, I assume it wants to see some CAN data from the original ECU...

Anyone shed any light on this ? Can the link replicate what is needs ?

Tried using a obd2 scanner to talk to the SRS system but no response.

ABS system is happy enough surprisingly and talking via obd2 port.

Dash displays Err HC(High speed canbus error)

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the abs system doesnt touch the ecm in factory wiring, and it also has no canbus in/out. It is just power, ground, a whole lot of outputs to the airbags, and a whole lot of inputs from crash sensors & seatbelt switches etc. It has 1x output to the dash for the failure light & 1x output to the 16pin data connector pin10 (not the normal ECU/canbus pin). Thats it. It looks like it has no idea whats going on with the rest of the car. If you dont have something that can read Airbag codes (maybe freeSSM?, not sure it can do airbags though). If you have a high end scan tool (eg autel/snapon/ADS/launch) that might work, otherwise maybe take it to a shop and have a real select monitor put across it? Otherwise start with power & ground checks.

The highspeed canbus error is probably because the dash or BIU is expecting signals from the ECU and not seeing them (ie you havent configured the right outputs), or because you havent wired the CAN lines to the ECU so its missing a terminating resistor.

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As Cj said, there is no comms between ecu and airbag system on 2005 MY subarus. You will need a better scanner to read it.  I would assume maybe a sensor got unplugged and is causing the fault.

As for the dash error, yes the canbus is unhappy but it is only for display functions such as temp gauge and tacho.  2005 was the first year that subaru implemented CAN into the legacy/liberty models.  But it is very limited and I wouldnt sweat it.  Maybe just add some gauges for the details you would want to see such as coolant temp, oil pressure/temp, and RPM.

I at one point had used a 07wrx plugin on a 2010 wrx drivetrain.  The I/O is all the same, just didnt have proper dash functionality.

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Ok thanks guys, I have found the airbag DTC section in the manual which should enable me to get codes and find whats wrong.

I did terminate/add resistor to the ECU end of the Subaru can bus, that actually made the fuel gauge respond to resistance at the tank end and stop flashing but it didn't clear the Err HC, I did not connect the Subaru can bus to the link, if i did does anyone know how to produce the can data to stop the dash error and make gauges work ?

Also its not listed in the ECU pinout but i have been told in the past that there is a speed signal(comes from ABSHU) at the ECU plug....anyone know what pin that might be ?

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There is no ABS -> ECU wire. It's a mistake in some of the wiring diagrams (either cluster or ABS) that show the wire also goes to the ECU, it doesnt. Its a Green/Black wire that goes ABS->dash. Pin 23 on the non VDC models and pin 36 on the VDC units (pin # on the ABS end). It does run a standard PWM out signal you could tap into if you didnt feel like connecting to the can bus. Easiest location to get at it is the "OP Connector" which is under the drivers dash in RHD models - its about a 4x4 big square plug that is usually either right above the brake pedal or near/behind the fuse box. It will just be sitting there unplugged form anything - find the Green/Black wire.

I've got the canbus ID's and a fair bit of the data identified I can send you - you should be able to sniff it from the canbus with the factory ECU connected with a $20 chinese canbus sniffer. There are 3x ID's the ECU normally sends out but you wont be able to exactly replicate the factory output from the link as there are some arbitrary counters etc. I suspect (But havent tried it) that if you broadcast the right id's it will keep the dash happy even if the data is mostly blank - I think at a minimum you would just read speed from canbus, and put coolant temp out + maybe some gauge warnings lights if you wanted. All other stuff is likely optional.

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Ok thanks for the info cj, I would of think the original ecu must get a speed signal from somewhere, maybe back from the dash through CAN ?

I would greatly appreciate the info you have on the Subaru CAN bus ID's etc,  I don't have a functional original ECU anymore as i cut the plug off it to make link harness ! It would be good to have the dash gauges functional and no error present, I do have the AIM MXS dash in the car, but that won't always be there for daily driving as I have had issues in the past with cowboy cops that see an aftermarket dash display and don't like it.... Cops in Western Australia have been a campaigning for a while now against modified cars, we have the toughesh laws in the country that basically don't let you do much with out full engineering and even then its very limited !

Cheers

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On 10/30/2019 at 12:17 AM, cj said:

There is no ABS -> ECU wire. It's a mistake in some of the wiring diagrams (either cluster or ABS) that show the wire also goes to the ECU, it doesnt. Its a Green/Black wire that goes ABS->dash. Pin 23 on the non VDC models and pin 36 on the VDC units (pin # on the ABS end). It does run a standard PWM out signal you could tap into if you didnt feel like connecting to the can bus. Easiest location to get at it is the "OP Connector" which is under the drivers dash in RHD models - its about a 4x4 big square plug that is usually either right above the brake pedal or near/behind the fuse box. It will just be sitting there unplugged form anything - find the Green/Black wire.

I've got the canbus ID's and a fair bit of the data identified I can send you - you should be able to sniff it from the canbus with the factory ECU connected with a $20 chinese canbus sniffer. There are 3x ID's the ECU normally sends out but you wont be able to exactly replicate the factory output from the link as there are some arbitrary counters etc. I suspect (But havent tried it) that if you broadcast the right id's it will keep the dash happy even if the data is mostly blank - I think at a minimum you would just read speed from canbus, and put coolant temp out + maybe some gauge warnings lights if you wanted. All other stuff is likely optional.

This info is very helpful for me and my project. I've got a 2005 Legacy GT that's undergoing a 1JZ swap, I've got most of the mechanical done, the engine wiring harness finished and pinned into the factory B21 and B20 bulkhead connectors, and I'm about to wire in my Link Fury. I'm wanting to retain the factory gauge cluster's functionality as much as possible, keeping the tacho and coolant temp gauges in tact, would you be willing to send me this can info you have as well? It would be greatly appreciated :).

Best,

Nick

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