[AnotherSubaruGuy]

2008 Outback 2.5i Limited w/ VDC. When I put the car into drive it moves forward but when I press the gas it just revs, it will accelerate under its own power and allow some throttle response once moving but if I give it too much gas it just revs higher. This is especially problematic when making a sharp turn, causing the car to be undrivable on public roads.

Background on the car: The guy I bought the car from said it needed a transmission. I found it had the WRONG transmission in it (one without VDC, code TZ1B8LFEBA) so I replaced it with the proper transmission (with VDC, code TV1B8MFEBA) and got 1,500 miles out of the replacement. I was driving, made a turn, the car revved without acceleration for a few seconds and slammed super hard into gear and threw all the dash lights. I limped back down the highway about 3 miles to my shop and that was that. Scanned and had a code for a pressure control solenoid (can't remember exact code) and decided to just replace the trans again.

I installed the next used replacement, and the first drive seemed like a big improvement until it got up to full temp and started doing the things mentioned in the first paragraph. Last time I scanned it I had codes C0045, C0022, C0052, no Pxxxx codes stored in the ECM or TCM. I figured there's no way this thing is just spitting out trannys so I replaced the TCM and it's still not fixed. Fluid level looks good and no noticeable faults in the wiring. Where else do I look or how do I go about about testing things? Any input is appreciated.

 

[1 Lucky Texan]

dunno what those codes are. any dents in the trans pan? you said fluid is OK but, and pardon me but have to ask - fluid level is checked while idling right?

when the trans has been replaced - did it include the front diff too?

a half axle popped partly out of the trans, or with certain kinds of failure, might do this.

 

[AnotherSubaruGuy]

2008 Outback Limited, 2.5 Auto w/ VDC

When I put the car in gear (1,2,D,R) it moves under its own power and will accelerate to +10 mph but doesn't respond to engine RPMs, almost like its slipping but it seems more like engine power is being cut. No lights on the dash but it has codes C0047 and C0071.

 

[SilverOnyx]

Why aren't you responding to your older thread about the same issue? You originally gave a lot more back story to the situation there. Making new threads for the same problem won't help.

If you have lost track of your old thread it's here: Gen 3 - Loss of Power/Slip When Aceelerating & Turning

 

[johnre]

Merged duplicate threads; moved to Gen 3 subforum.

Please, one thread start per subject.

And - welcome to the Subaru Outback forums!

 

[AnotherSubaruGuy]

The new and only codes are for the Steering Angle Sensor and the other one I believe is a VDC module fault/communication error. Pan looks free of dents and I've checked the fluid at idle, both cold and once up to temp. The diff stayed with the trans each time as well and both front CV axles are newer and intact. I'm really thinking it's something electrical causing engine power to be cut and not sent to the wheels, I'm just not sure how to start diagnosis.

Why aren't you responding to your older thread about the same issue? You originally gave a lot more back story to the situation there. Making new threads for the same problem won't help.

I've been checking the orignal thread but somehow I wasn't getting updates that anyone replied so I tried again, without all the words to scare everyone off

 

[seagrass]

Do not overthink the problem.

Subaru modules (ECU, TCU, VDC, BIU, etc) rarely fail. You are far more likely to be having a problem with wiring, electrical connectors or earth/ground connections.

As you mention you have communication problems you need to start with battery. battery cables, and the eight to ten ground/earth connections in the engine bay. These connections all need to be clean, tight and free of corrosion.

You need to remove all the ground/earth connections and clean the earth connector and vehicle frame where the connector bolts to. There are two earth/ground connections on the inlet manifold, one on the firewall, one from each head to the frame rail, one to each side of the engine bay and the main earth/ground cable from the battery.

Once you have all these clean you need to test the battery using a CCA tester and compare the actual CCA of the battery to the rated CCA. This will give you a pass or fail result.

All of the modules and sensors on a Subaru rely on good ground/earth connections to work properly. Bad/poor ground/earth connections equals multiple communication problems.

Seagrass

 

[AnotherSubaruGuy]

Thank you guys for the input, I will start checking grounds and more fuses tomorrow. The only thing that has me leaning on a fried module is the fact that the wrong transmission was installed by the previous owner and the car was driven maybe 200 miles with the non VDC trans in it.

 

[seagrass]

Thank you guys for the input, I will start checking grounds and more fuses tomorrow. The only thing that has me leaning on a fried module is the fact that the wrong transmission was installed by the previous owner and the car was driven maybe 200 miles with the non VDC trans in it.

It is doubtful that the wrong transmission would cause a transmission control module to fail.

It is far more likely for a transmission to fail with the wrong TCU as the TCU would be failing to control the transmission correctly.

Seagrass

 

[johnre]

Why aren't you responding to your older thread about the same issue? You originally gave a lot more back story to the situation there. Making new threads for the same problem won't help.

I've been checking the orignal thread but somehow I wasn't getting updates that anyone replied so I tried again, without all the words to scare everyone off

You can achieve exactly the same effect by bumping your own original post with another short appeal for help - typically this takes the form of "No response; does anyone know?". It will then appear in the list of New Posts and be read, and in many cases, people who had hung back the first time they read it, thinking someone else was more qualified to respond, will then jump into the thread themselves.

Posting in a new thread without the details will not achieve this, as most of us don't recall your first, lengthier post, so we don't go back and read it. @SilverOnyx is rather unique here; he remembers everything, I think.

 

[SilverOnyx]

When I asked you to get back to your original thread it was trying to help you get answers, not trying to scold you.

When asking for help with a fairly technical issue, there are only about a dozen deeply knowledgeable active forum members and you have to be patient, and respond to anyone who engages in your thread to keep it active. Realize that fellow forum members are only trying to help. If they ask a question, answer it. If you can provide even more detail it may help get additional responses, but less information doesn't get you better responses.

I'm active but highly technical things are way over my head - sometimes I ask clarifying questions that come to mind not because I think I have the answer, but I'm trying to help the original poster provide more context so that the more skilled people have information to provide better responses.

 

[AnotherSubaruGuy]

Right on guys, got it. And no worries Onyx, wasn't trying to be difficult and I didn't take anything as a scolding lol not sure where you picked up on that, I guess things just get misconstrued communicating on the internet.

Anyways, I cleaned up the grounds and in the process found a mouse chewed on the spark plug wire at the coil, again. 'Minor' detail I forgot to mention in my orignal post because it was already so long was: a mouse had chewed through #2 plug wire about 2 weeks ago and also nibbled through the black loom around the crank sensor harness and got a few strands of the wire, I dealt with those items at that time. The rest of the harness in the engine bay 'looks' fine and I checked the wiring to the ECM too. This chewing thing only happened after the most recent breakdown, but it may be mice I've been up against all along.
I will update as I find out more. Sorry if this is confusing, I'm trying to be specific

 

[AnotherSubaruGuy]

So I cleaned all the grounds and that didn't work. I got it on the on the lift to check for anything suspicious underneath and I put it in gear just to see what would happen. In park the wheels were spinning, can't recall if that's normal, but more importantly in drive it seemed to be letting the power go to the wheels as I revved the engine like it should be when all 4 wheels are in the ground. But, when I pressed the brake the ABS kicked in and stopped me from pushing the brake pedal down, which didn't seem or sound normal at all. I let the car down and took it for a drive, and it was running like a champ. I gave it some good gas on our gravel driveway and caused some wheel spin then the red BRAKE, traction, and I think AWD lights flashed for a split second, and it went back to doing the revving/slipping thing. No lights illuminated in cluster, still pulling codes C0071, C0047 and a new C0051.

 

[seagrass]

None of these codes refer to the transmission. They are all “C” codes which are loss of communication to varying modules.

The brake, AWD and traction control lights (often with others) are displayed to alert you the vehicle monitoring systems have detected a problem. The lights that are on in the instrument cluster also show which vehicle systems are now no longer functioning. These systems are disabled to protect those systems and to try and prevent further damage.

The C0071 code is a steering angle sensor code,

The C0047 and C0051 codes are both ABS codes. These codes may be the result of you having the vehicle in the air and applying the brakes (just a thought and this may not be the case).

I suggest you disconnect the battery for around 15 minutes to reset the ECU (or reset with your scan tool if you have one) and then monitor what happens when you next drive the vehicle.

Seagrass

 

[plain OM]

Some observations, comments, . . .

In park the wheels were spinning, can't recall if that's normal, . . .

All four? When in Park, the front wheels should not be turning. The parking pawl in the tail section engages a gear tand pinion shaft connected to the front differential. The pawl prevents the gear from turning, and therefore the front drive from turning. Are you sure this was in Park?

. . . in drive . . . it seemed to be letting the power go to the wheels as I revved the engine like it should be when all 4 wheels are in the ground

Very little torque is required to turn the wheels when they're raised. This doesn't simulate the conditions when the car is on the ground and a lot more torque is needed to move the car.

. . . when I pressed the brake the ABS kicked in . . .

To be expected. When the pedal is pressed with the car raised, one wheel could stop while the others continue to turn. To the ABS, that's a skidding wheel and so the ABS kicks in to control the "skid".

When the car is being driven, and the accelerator pedal is pressed down, engine torque is increased, and there should be a corresponding acceleration of the car. If the engine revs up, without any corresponding acceleration, there is some sort of "disconnect" between the engine output and the wheels. This could be in the engine/torque converter connection, the torque converter, the transmission gear set, or the drive train to the front or rear wheels (drive shafts, differentials, axles). The converter and transmission are less likely if two transmissions with their own torque converters were installed properly and the car is exhibiting identical symptoms. All the more so if the car had the exact same symptoms when first purchased, before changing the tranny. That essentially leaves the drive trains to the front and rear wheels.

There have been cases of a CV joint in an axle failing, but not falling apart. Visually it looks fine. Moreover, if one twists the two ends of the axle by hand, it might seem intact because of residual friction in the joint. But when that twisting involves higher torque, the joint begins to slip, and torque transfer is lost. The part that is connected to the differential spins freely, and that reduces the torque available to other wheels. The engine revs but the car doesn't accelerate. Similar symptoms could be experienced if an axle has pulled out of the differential. A movement of about 1/4" is enough to disengage the splines on the axle from the splines in the differential side gear. The axle appears to be in place (not hanging down), but it's not connected inside. I'm not saying these are your problem, but the symptoms would be similar to what you experienced, especially most recently when you "gave it some good gas on our gravel driveway. . . "

 

[AnotherSubaruGuy]

I left the battery disconnected overnight while I cleaned the grounds and didn't have any improvement on start up.

It was in Park on the lift, but it was only the rear wheels spinning.

The weird thing is the throttle response felt normal with the wheels off the ground, then when I lowered it down and drove it again it felt normal like the test drive after installing this current tranny. After I caused TC/VDC to kick, it went back to little to no power going to the wheels unless I gun it from a dig, then it will spin the tires.

Not to sound like a smart guy, but these cars are all I work on and I don't think I've seen the ABS kick in like that before. I mean I really had to fight with that pedal to stop the wheels.

When I first purchased the car it actually drove pretty normally but would slip under hard acceleration and kinda hunt for gears, and it had a Christmas tree for an instrument cluster. But it was not doing what it's doing now.

With it being intermittent like it is I don't feel like it's a mechanical part failing, but I could be wrong. When I press the gas and the brake at same time I can feel it build torque, and like I said it will spin tires from a dig but bog out.

I really do appreciate all of your guys' help and time

 

[seagrass]

Once you get a DTC the vehicle goes into “limp mode” with reduced power and and many “safety features” are disabled.

You need to diagnose why you are getting the “C” codes, resolve that problem and then go on to the next problem.

As I said previously “C” codes are communication codes (loss of communication with sensor or module). These are typically caused by electrical problems (battery, earth/ground, wiring or connectors). Follow the codes to find the cause of the problem.

Seagrass

 

[1 Lucky Texan]

did the car get a replacement trans or rear diff in the past?

tires all the same size/brand/model?

 

[AnotherSubaruGuy]

Yes all tires are within even wear and the trans has been replaced 3 times now, but the diff is original to my knowledge. Would anyone be able to help me out with the diagnostic tree from the FSM on C0045?

 

[plain OM]

C0045 has two source possibilities, according to the attached diagnostic tree. In both cases the symptoms are ABS/VDC not operating.

TC adjusts engine torque to conditions (e.g., slip/slide) by limiting engine fuel and/or throttle. Your reports say that the engine revs when the accelerator is pressed, which doesn't seem to suggest TC coming into play.