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Bulkhead Wiring Harness Replacement 2014 Forester


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We will certainly be leaving a review and reaching out to management.

I was able to get a written statement from the tech outlining the steps taken to troubleshoot and their data. I don't know a whole lot about it, but it seems like it was thorough.

 

I have one quote back that's cheaper and they are a Subaru only mechanic, just not a dealership.

 

From the tech:

Vehicle presented with intermittent issue of multiple warning lights and no data being sent to combination meter or multi-funtion display, also has no power steering assist. Upon further inspection tech found there is no communication with engine control module (ECM), Airbag system (AB), or occupant detection system (ODS). When fault is occuring, on top of the symptoms listed above, multiple DTCs are stored in various computer modules (CM). Current DTCs as follows: Body control (BIU) - U0073, U0100, U1202. Power steering(P/S) - C2543, U0073, U0100. Multi-function display U1201. Note when fault occurs DTCs and symptoms will sometimes varry depending on how interupted data signal is on CAN BUS. Some past DTCs are stored related to issue, however these DTCs are moot as then cannot be diagnosed in a past fault condition.  All DTCs indicated a CAN fault of no communication with ECM or Airbag systems. Sometimes data can be sent from CM, however during fault all communication (ability to "talk" to CMs) is disrupted. 
 
Based upon time stamp and trip counter of current DTCs list tech proceeded with diagnosis of most recently set DTC U0073. Note all DTCs eventually lead to same diagnostic path. Inspected resistance of of network at DLC connector, pins 6 & 14, which indicates 90 ohms of resistance (spec is ~60ohms during normal operation). Voltage at pin 6 to ground is 0v, pin 14 to ground 2.6v (using DVOM voltage should avergae to 2.5v on both pin 6 and 14, lab scope would show more fluction of signal between 1.5-3.5v) Using CAN diagnositc table (bubble chart) provided by Subaru, the location of the CAN BUS fault is isolated to CAN BUS High data line around junctions near "6" and "7" on the provided chart. The junctions located in the area are indentified at connectors B258 and B247 for CAN High data lines. Seeing as there is no communication to ECM and AB CM (at B258), however communication is possible to P/S (at B247), this supports the fault point of between B258 and B247 or at junction B258. With P/S, AB, and ECM disconnected, CAN BUS High isolated from P/S to ECM, when the fault is occuring tech found 3 ohms of resistance in the segment of the CAN BUS High (spec ~0.2ohm) [B450#6 to B137#19 3ohms]. While monitoring resistance from P/S to ECM, tech found resistance would change as the harness was manipulated (moved/shaken) the resistance would intermittently change. To rule out fault of CAN BUS Low tech measured from DLC pin 14 to ECM pin 18 and resistance is within spec at 0.2ohms. [B137#18 to B40 #14]. To verifiy a CM is not interupting, or pulling down CAN BUS voltage, tech disconnected one CM at a time to see if communication comes back to ECM or AB, which it did not. All tests further supports a fault in the CAN BUS network at J/C B258 (bulkhead wiring harness).  Unfortunately based upon the location of J/C B258 it is no easily accessible, as it's located behind the dash and heater core assembly, so deductive reasoning must be used to isolate and diagnosis this fault location. Listed below are the most significate and relevant electrical checks performed, as well as DTC descriptions. 
 
This diagnosis and findings have been verified with Subaru Techline and the DSQM of SOA. In my expereienced opionion, it's my conculsion, The only way to guarantee a proper and accurate fix for this CAN BUS fault is replacement of the bulkhead wiring harness. Replacement of ECM can be starting point, however diagnositcs does not support this will resolve the fault. All diagnostics provided by Subaru are just starting points and analytical reasoning must be used for final decision. See attached documents and media on inspection for further supporting information.
 
Note the vehicle is not equipped with keyless access CM, remote start CM, (separate) yaw rate/g sensor, auto headlight leveler CM, eyesight camera CM, or (auto) A/C CM. Aftermarket electronics installed include (ruled out as influence or cause of fault) radio, LED high beams, LED low beams with wiring harness, LED light bar, audio amplifier. Possible subwoofer and speakers installed, however unable to verify without removal of items in back of vehicle or door card removal. 
 
DTC:
U0073 - Control module communication bus off
U0100 - Lost communication with ECM/PCM "A"
U1201 - CAN-HS counter abnormal
C2543 - Error passive
 
Checks (at time of fault, performed with CAN BUS isolated):
B40#6-#14 - 90ohms
B40#6 to ground - 0v
B40#14 to ground - 2.6v
B40#14 to B137#18 - 0.3ohms
B40#6 to B137#19 - 3ohms
B450#6 to B137#19 - 3ohms
B450#7 to B137#18 - 0.2ohms
B247 to B137#19 - 3ohms
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49 minutes ago, Daskuppler said:

 

From the tech:

Vehicle presented with intermittent issue of multiple warning lights and no
 

Wow that’s awesome.  Thanks for posting that. That’s interesting to see their diagnostic depth and some notes on verifying communication with Subaru higher ups. Very cool. Sorry of course this is not at all awesome or cool for you. 

The “symptoms changed when wiggled” nearly guarantees a very short area of wire or connector damage.  That’s how I used to diagnose wiring problems on old Gen 1980s Subarus. I’ve found engine wiring harness/connector failures that way in those.  wiggle the wires until the engine runs differently, or it alternates from starts/doesn’t start, and you found the short. But those have all been 25+ year old old Gen with green corrosion inside the wire insulation and much lower grade connectors than modern Subarus.

Every time it’s been a harness plug issue or the wiring within 2-3” of the harness. 

Yours being newer won’t have those issues but still wouldn’t surprise me if it’s close to a connector or that firewall pass through. It won’t be at a random spot mid-loom. 

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1 hour ago, idosubaru said:

Wow that’s awesome.  Thanks for posting that. That’s interesting to see their diagnostic depth and some notes on verifying communication with Subaru higher ups. Very cool. Sorry of course this is not at all awesome or cool for you. 

The “symptoms changed when wiggled” nearly guarantees a very short area of wire or connector damage.  That’s how I used to diagnose wiring problems on old Gen 1980s Subarus. I’ve found engine wiring harness/connector failures that way in those.  wiggle the wires until the engine runs differently, or it alternates from starts/doesn’t start, and you found the short. But those have all been 25+ year old old Gen with green corrosion inside the wire insulation and much lower grade connectors than modern Subarus.

Every time it’s been a harness plug issue or the wiring within 2-3” of the harness. 

Yours being newer won’t have those issues but still wouldn’t surprise me if it’s close to a connector or that firewall pass through. It won’t be at a random spot mid-loom. 

Yeah, it was good I formation. I thought. Maybe someone could benefit from a little inside knowledge. It all seems logical to me. The harness seems to go through the firewall in 3 or 4 spots.

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12 minutes ago, Daskuppler said:

Yeah, it was good I formation. I thought. Maybe someone could benefit from a little inside knowledge. It all seems logical to me. The harness seems to go through the firewall in 3 or 4 spots.

I’d love to be able to diagnose like that. Drool.  

I’m working on another Subaru tomorrow if I think about it I’ll peak at my 14 Forester parts car 

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I wonder if there’s enough wiring behind each plug to strip the wiring to check for shorts in that 2-3 inches behind the plug that @idosubaru talks about. 

^ that could save a pot load of time and money fixing this issue than pulling out the whole dashboard and replacing that bulkhead wiring loom. 

Also impressed with those notes from the diagnostics. It does borderline on too much info/words that could turn many owners away from actually reading and trying to understand. 

It feels like a bit of a step forward from my end.

Cheers 

Bennie

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7 hours ago, el_freddo said:

I wonder if there’s enough wiring behind each plug to strip the wiring to check for shorts in that 2-3 inches behind the plug that @idosubaru talks about. 

^ that could save a pot load of time and money fixing this issue than pulling out the whole dashboard and replacing that bulkhead wiring loom. 

Also impressed with those notes from the diagnostics. It does borderline on too much info/words that could turn many owners away from actually reading and trying to understand. 

It feels like a bit of a step forward from my end.

Cheers 

Bennie

The dealership definitely redeemed themselves a bit with the email.  The tech is clearly insanely knowledgeable, but he is a senior master tech so I would hope he is.  My only concern with a fix like that is the potential for future failure.  We are hard on this car and it sees a lot of dirt roads and gets run pretty hard.  If it was anywhere but behind the heater core, this would all be much easier.

9 hours ago, idosubaru said:

I’d love to be able to diagnose like that. Drool.  

I’m working on another Subaru tomorrow if I think about it I’ll peak at my 14 Forester parts car 

It would be amazing to be that knowledgeable!

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  • 2 weeks later...
On 1/25/2024 at 10:28 PM, Daskuppler said:

Picked up the car today. Heater didn't work. I figured they forgot to clip in the temperature control cable behind the glove box... Turns out they broke the clip, ziptied it and it didn't work...

What a saga! ?

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  • 2 weeks later...

A weird bump/popping has developed in the steering column. It feels like it is coming from directly behind the steering wheel and is inaudible. It only happens when the wheel is turned more than 75% to lock in either direction. The steering wheel feels like it is actually shifting in its plane of operation. Does the dash removal require the steering column to be removed in these vehicles (I know it does in other Subarus).

Edited by Daskuppler
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Idosubaru... I'm confused as well. I'm not sure sure how to describe it, but it happens when tires are rolling and stationary. It is independent of road conditions. I guess I'll contact the delightful dealership again.

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Here's a video...

 

It's getting worse, I'm assuming they forgot to torque the steering column brace, but I don't dare tear anything apart and get blamed for whatever else they have messed up or forgotten to do.

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13 hours ago, Daskuppler said:

Here's a video...

It's getting worse, I'm assuming they forgot to torque the steering column brace, but I don't dare tear anything apart and get blamed for whatever else they have messed up or forgotten to do.

Wow, I imagine they'll jump right in and fix that.  Seems like it had to be something that happened during that job.

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1 hour ago, idosubaru said:

Wow, I imagine they'll jump right in and fix that.  Seems like it had to be something that happened during that job.

One would hope... So far they're ignoring me, but someone will eventually care given it's a safety issue

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20 hours ago, Daskuppler said:

One would hope... So far they're ignoring me, but someone will eventually care given it's a safety issue

Email them the link to the YouTube video. That might get them moving with some action. 

Cheers 

Bennie

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3 hours ago, el_freddo said:

Email them the link to the YouTube video. That might get them moving with some action. 

Cheers 

Bennie

I got a hold of the manager, tow truck showed up this morning and it's already in a bay. Hopefully it's as simple as just tightening a couple bolts.

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On 2/14/2024 at 10:18 AM, Daskuppler said:

I got a hold of the manager, tow truck showed up this morning and it's already in a bay. Hopefully it's as simple as just tightening a couple bolts.

Eventually you’ll have more miles than trips to the shop on this car. ?!?!?!?!?  Lol SMH

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15 hours ago, idosubaru said:

Eventually you’ll have more miles than trips to the shop on this car. ?!?!?!?!?  Lol SMH

hahaha! so far so good on this round.  We've got 300 miles on it since it was there last and it doesn't need to go back yet lol

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On 2/17/2024 at 9:12 AM, 88SubGL said:

Now’s the time to sell! Haha

If only there was something decent around to buy. Used Subarus are worth a small fortune around here... With 300k on them. Once I'm done with the head gaskets on my 02 tomorrow, it will start to take the brunt of the mileage

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16 hours ago, 88SubGL said:

Because he’s had so many problems with this car and right now it’s running ok and nothing is falling apart at the moment. Time to sell! Haha

And then buy what? Another car with someone else’s issues? 

I’d keep the vehicle you’ve ironed the issues out of. Otherwise trade it in at a dealership for a new vehicle and let them deal with it. 

Cheers 

Bennie

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7 hours ago, el_freddo said:

And then buy what?

Another Subaru that that dealer hasn’t touched, because that dealership seems to be the source of most of the problems. 

 

7 hours ago, el_freddo said:

I’d keep the vehicle you’ve ironed the issues out of.

Are the issues all ironed out now?

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3 hours ago, 88SubGL said:

Another Subaru that that dealer hasn’t touched, because that dealership seems to be the source of most of the problems. 

 

Are the issues all ironed out now?

So far.. almost 1000 miles on it and it's issue free.

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