ABS Light Frustration

[yeltsew]

Hey Guys! I just bought an 06 LGT last Monday, and one of the issues I've encountered so far is that the ABS light is on. Of course, my cruise control doesn't work and I've seen conflicting information online about whether this changes changes the way the engine runs. (Disabling boost control for "safety" in case the ABS isn't working?) I figured it was just a wheel speed sensor or something simple, but when I got home and did the gauge cluster test, the codes it gave were for:

• C0118 - Faulty G sensor output voltage
• C0114 - Defective valve relay

The factory service manual has a few tests for each, and I've gone through the ones that don't require SSM as much as I can. On the G sensor, the voltages seem fine when holding it at different angles. I checked for continuity between the G sensor pins and 24, 21, and 10 on ABS module connector and everything seems good there. I even ordered a used one on Ebay to see if maybe there was just something bad with the old one, since it was a relatively cheap sanity check, and the code is still there after disconnecting the battery for 15 minutes.

For the valve relay, I checked the voltages on the connector and it seemed to have voltage and a good ground where it should. The only thing that didn't match the manual exactly was the internal resistance of the relay, which read OL as opposed to a specific resistance above 1MΩ, but I figure that's just discrepancies between how the manual was written and how my meter reads.

The only other thing I can really think is maybe some other part of the ABS module is bad and sending bad readings to the ECU for the other components? If I have to replace the ABS module, that's not a huge deal, but I'd hate to order one and go through the process of bleeding the brakes all over for the codes to still be there. Does anyone know if the ABS module has to be coded to the car in any way, or will one from any MT Legacy work?

Some pics of the car for attention, replacement headlights are coming in tomorrow:

 

Edited August 22, 2023 by yeltsew

[Mr. Electric Wizard]

Can't help you but I can commiserate.  I thought I fixed my ABS light when I found that the front passenger side had a broken wire, but I re-soldered it and the light is still on.  Going to take the car to a local shop tomorrow so that they can smoke the intake and hopefully get this car running right.  I didn't realize that the ABS could affect the way the car runs, but reading your post makes me think...

[yeltsew]

It's funny you mention that, I got the car smoke tested yesterday because the idle is funky and it's not boosting over ~10psi, I assume wastegate pressure. They found a vacuum leak on one of the hoses that runs under the intake manifold, which I had to order from Subaru. Knowing that, I have less suspicion the ABS code is making it run funky.

Still haven't been able to figure out what the issue is though.

[Mr. Electric Wizard]

Cool.  Mine was dropped off to a Subaru specific shop yesterday.  I'll let you know what the issue ends up being hopefully.

[Mr. Electric Wizard]

My smoke test revealed a slight leak at the new recirculating blow off valve I installed.  I didn't seat the gasket properly when I installed it.  I was paranoid about spinning the threaded insert on the intercooler so I didn't manhandle the bolts.  Also smoke came out of one of the injectors that I was having some misfire codes on and I knew it wasn't the coil.  That injector had been taken out at one point recently.  Thinking the wrong oring got installed when we put it back in.  Anyways, they're going to diagnose the ABS light while they have it. 

[yeltsew]

I can say in this case, the ABS light does NOT change the way it runs. I replaced a bunch of vacuum lines today and the car's back to making good power. Good luck on fixing all of yours.

For now, I'm a little less concerned about the ABS light, but I still wish I could figure out what the problem is. 541 Motorsports has an ABS module from an 05 MT car for pretty cheap, so I might just bite the bullet and try replacing it.

Edited August 26, 2023 by yeltsew

[Mr. Electric Wizard]

ABS light fixed!  The left rear (I think) was intermittently working.  I had the shop just go ahead and replace it with a used one they had on a parts car there.