Limp Mode 2005 Subaru Outback 2.5

I am running out of ideas. I have a 2005 Subaru Outback and a while back I had to replace a drive shaft. After replacing it my car goes into limp mode and I get a different random code every time. The car seems to run fine when it is cold but after it warms up it will go into limp mode randomly. If I cost to a stop and shut down the car and wait a while to restart it runs fine. I’ve tried and researched just about everything thing. Any help would be greatly appreciated.

Are you sure the codes are random? What have the exact codes been? Who has read the codes and have you had an actual transmission shop look at it?

Can you describe what you mean by limp mode? I assume that “If I cost to a stop” was a typo & should read “coast” to a stop. In limp mode you will be in gear and won’t need to coast so perhaps you could clarify.

Does the car have ABS? If so, was the new drive shaft built for ABS? Most of these will have speed sensors on them for the ABS system, but that speed sensor info can also be used in some transmission control systems. If the tone ring is absent or damaged and/or if the wheel speed sensor was damaged or disrupted during the axle change this can spell trouble.

Cigroller stole the words right out of my mouth. Are we talking about a DRIVESHAFT or an AXLE here? A driveshaft replacement doesnt occur very often or rather AT ALL in these vehicles.

If we are talking about an AXLE…then they may have used a NON-ABS axle instead of the needed ABS Axle…if this is the case then yes you absolutely need to have the correct axle installed…

IF you DO HAVE ABS…then the axle intended for ABS vehicles has a bunch of little grooves cut into the end that goes to the wheel…a sensor reads these notches…when it doesnt see them wizzing by it immediately throws and ABS code… You need to find out about your vehicle having ABS or not…if so…see if you can see the notches on the axle end…they need to be there if you have ABS system

@cigroller, @honda blackbird,

Firstly yes my apologies “cost” was a typo and should have read “coast” also yes axle is what was replaced.

Secondly yes the car does have ABS. The problem did not start to occur until replacing the axle. But cannot say that the problem is caused by that or that it wouldn’t have occurred if I didn’t have to have it replaced.

Thirdly let me apologize and I will try to explain better. My car will randomly go into Limp Mode. Mostly when at a stop; seldom when driving. When it goes into “limp mode” the car will “buck” once and the RPM will fluctuate between 500 to 4000 (in D or N) for a few mins before the CEL illuminates. Eventually the acceleration pedal will go inoperable. At this point I have to pull over and shut down the car and restart it to bring it back to normal. It will send out a code. I have received:
“P0301 Cylinder 1 Misfire detected”
“P0302 Cylinder 2 Misfire detected”
“P0303 Cylinder 3 Misfire detected”
“P0304 Cylinder 4 Misfire detected”

and the most recent one of

“P0638 Throttle Actuator Control Range/ Performance (Bank 1)”

which is why I say its random.

I have cleaned the MAF and TB and changed the plug and wires. The car will run fine with no issue until it reaches normal operating temperature. Hope the re-explanation helps.

WOW…this is funky. I think I am at a loss here…which doesn’t happen often. LOL… Wish I could get my hands on this vehicle to see whats going on here…sounds like several things at once really. The axle shouldn’t be able to do all of this even if it desperately wanted to…then again…wait…if the axle is not an ABS unit…it may be throwing the engine and trans ECU into a fit because it thinks that 3 wheels are rotating while one is locked up…which if I were an engine ecu…I would not like very much…

What do you think about them apples guys? I mean if the trans and engine ecu all think they are cruising down the road at 45-50 mph with one wheel locked up I think the vehicle would try to stop you…dont you?

Then at that point all the subsequent codes are just a result of the limp mode being engaged…could be Wabbit…could be…

I’m grasping at straws but maybe all that jostling around of getting the drive shaft out caused a ground to not make good contact?
There are several ground contacts going to the engine, transmission, etc. On the FSM it shows that some sensors - including the wheel speed sensors - have electrical shields, all tied to ground.

If one ground is loose, missing or making intermittent contact, it could potentially introduce electrical noise and cause all sorts of weird issues.

I don’t think those are “random” codes. I think that you have a problem with your throttle by wire system. I think that problem is probably throwing off the PCM and then creating misfire conditions. (E.g. bad throttle position info maybe creating too rich or lean a mixture leading to misfire).

Here is a great resource:

Take out your voltmeter and a thinking cap. Either that or get it on a scantool to access live data on throttle position, MAF readings, fuel mix, etc.