Complex BRZ Electrical/ECU Issue -- Need help!

[mackemode]

I picked up a 2015 Subaru BRZ Limited from a preowned dealership last week in “As Is” condition. I bought the car knowing it had issues, but I got for a good price. When I purchased it, it was having idling/RPM stutter kind of issues and throwing CEL Codes P0102 and P0113. I assumed both of these had to do with the aftermarket Takeda Momentum air intake and the sensors associated with it.

After trailering the car home and looking into the codes more, I realized it was more of an electrical/voltage issue and decided it was over my head to try to fix myself, and took it into a local shop.

The local shop told me the car is having a much larger wiring/electrical/computer issue. They said even their Subaru specific diagnostic wouldn’t communicate with the car’s ECU/computer. They recommended I take it to a dealership, but sadly the nearest Subaru is 2 hours from me and would require towing and multiple trips back and forth. I figured I would ask around to some FRS/BRZ owners to see if this is any sort of common or known issue before doing so.

Here’s the full list of symptoms/things I know about the car so far:

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- The car dies on the first five starts, every single time. It will kill itself after about about half a second of idling until the sixth startup, where it allows itself to run and idle perfectly fine. It’s the sixth time, every single time. Security shutoffs maybe?

- The check engine light does not always come on immediately after clearing codes with an OBD2 scanner. I’ve drove it 30 miles or so since last time I reset the codes, and the check engine light has not come on again, nor have I had any stuttering/idling/RPM issues. The startup issue has remained consistent though.

- When the check engine light is on, it will throw codes P0102 and P0113, related to the voltages of the MAF and AIT sensors.

- When I purchased the car, the dealership told me they bought it from an auction where the dash was torn apart and the wiring was “messed with.”

- When I first drove the car, I noticed the traction control / sport mode buttons wouldn’t do anything. I found the module was unplugged. Even after plugging in, the traction control button only works maybe half the time.

- Knowing this about the traction control button, I tried to break the tires loose today in the rain with the traction control “off”, when the button was working. As soon as the tires broke loose, the traction control turned back on by itself (turned the light off on the cluster) and the car caught itself out of wheel spin and cut the throttle. I thought this was very odd, that button should be a full override, correct?

- The automatic lock on the driver side does not work with the door button, nor the key fob. When walking up to the car and placing your hand on the door handle, the unlock beep happens 5 times in a row, but the door does not unlock. I have to use the key from inside the fob to unlock the car from the outside.

- The other day when I drove it across town to the shop, the car completely died and the dash lit up with just about every light possible. It stuttered for a bit and then just shut off. I turned the car off, back on, and it started right back up and had no other issues the rest of the drive (~10 miles), just had check engine light on.

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I don’t know which of these issues are interconnected to a larger wiring issue (maybe all) but something is going on with the car that is way above my head. Will definitely be taking it to another shop or dealership, but figured I would ask here and see if this is any sort of common or known issue.

Does anyone have any ideas what may be wrong based on these symptoms?

Any help is appreciated!

[p1l0t]

You could just take a $100 gamble on a new MAF sensor and if that doesn't work return it. (although it never hurts to replace your MAF once in awhile anyway). If you really want to be frugal you can try cleaning and putting back in and/or watching some youtube vids on how to test them. All depends on whether you have more of time or money spend. (Having a brand new can help with the testing too though). Myself I just buy stuff if it's cheap and if that wasn't the problem and the voltage readouts match the new one I keep the old one in inventory for a rainy day and move on to the next sensor.

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[p1l0t]

My 03' WRX I went through like 3 of them. Once it failed completely, once it was throwing intermittent codes, and once the tuner was like.. you know we could better woth a new MAF...

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[p1l0t]

P.S.
Don't worry that car 168k miles on it and was still beasting stock STis until I got rear-ended on highway traffic jam. But yeah as cars get older electronic components go wacky sometimes.

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[mackemode]

Definitely worth a shot, but the other electrical issues are really making me feel like it's not the intake or MAF. The startup issue alone (5 failed starts, every time) is soooo odd to me. Feel like it's something wiring/ECU based, especially since the local shop couldn't get their diagnostic to run.

[solidsnake11]

Check all grounds inside and out.
You can use a multimeter and hook one end to the - battery terminal and then touch it to the ground locations.
Example touch to block should be close to 0 resistance.
Then the bolts on the body.
Is it a flood car?

[p1l0t]

Another thing too is check if the MAF is the OEM sensor or cheap replacement. The cheap ones don't last long, and are terrible for tuning. Those and cam position sensors are the most fallible things, then coil packs. From your codes my guess is the MAF though but you can try other things like grounding mentioned above or just cleaning the connectors on the MAF first of course before you go throwing money at it. If you have a multimeter is worth using it!

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[Immaculate Fury]

Replace the air intake temperature sensor as well. The car is giving you those codes for a reason. Maybe replacing both of those sensors will fix the issue. Especially since they both relate to the computers incoming air measurement. Without the MAF, it has no idea how much flow is coming in. Without the AIT it has no idea what volume the air is

[JohnH]

Check each and all grounds you can find. really dig into it.

Look for any rubs, chews, cuts, corrosion on any and all wiring.

if none of these things are found, or if found and repaired, and the car still does the same, I suspect you may have a bad PCM. If the scantool won't communicate with the PCM, and all the wiring and connectors are good, it almost has to be a PCM issue. Especially if intermittent like you are talking about.

You COULD pull the pcm, take it apart(if possible?) and look for a crappy solder or several of them. I've repaired several different PCMs and other modules by fixing bad solders.

Of course this and every other post on here is conjecture and (educated?) guesses as we don't have the car to look at.

PS, I am a Red Seal automotive tech, so I am payed to fix crap like this. Don't guess, and follow a logical course of action.

[p1l0t]

Originally Posted by JohnH

PS, I am a Red Seal automotive tech, so I am payed to fix crap like this. Don't guess, and follow a logical course of action.

Is that like the Navy Seals of automotive technicians?

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[Immaculate Fury]

Originally Posted by p1l0t

Is that like the Navy Seals of automotive technicians?

No, that's a term in Canada used for someone who has got their red seal journeyman ticket in a trade. Means they've served 4 years in the workforce and schooling then taken the red seal test afterwards

Edit: just realised this might have been sarcasm... Oops. That's what I get for forum-ing on a night shift

[p1l0t]

Originally Posted by Immaculate Fury

No, that's a term in Canada used for someone who has got their red seal journeyman ticket in a trade. Means they've served 4 years in the workforce and schooling then taken the red seal test afterwards

Edit: just realised this might have been sarcasm... Oops. That's what I get for forum-ing on a night shift

Haha it was kind of being funny, (nobody likes my jokes). Down here in the states we have ASE certification though so I never heard Red Seal before.

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[Kodename47]

Originally Posted by Immaculate Fury

Replace the air intake temperature sensor as well.

The IAT sensor is part of the MAF sensor, it's not separate.

[soundman98]

apparently, the issue is either fixed, or burned up in a meteor strike.