Code P2138/Throttle position Sensor - Subaru Outback - Subaru Outback Forums
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post #1 of 88 (permalink) Old 05-16-2010, 10:11 PM Thread Starter
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Code P2138/Throttle position Sensor

Unfortunately my 2006 Outback/Legacy LL Bean edition has had this problem for 3 months now, it comes and goes, the check engine light comes on and car goes limp, gas pedal stops working, let it sit and it will start and gas pedal works; dealership couldn't even figure it out...a code that has shown up is P2138 I have heard it is the gas pedal position sensor? Local mechanic thought it was the computer; used one is $400, I am not interested in that option. Any help would be appreciated.

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post #2 of 88 (permalink) Old 05-17-2010, 01:42 AM
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Gotta love drive-by-wire.

The service manual has an 18-step diagnostic procedure for this code. It mostly comes down to repairing the harness/connectors or replacing the accelerator pedal sensor. Replacing the ECM is a last resort if everything, and I mean everything, else checks out.


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post #3 of 88 (permalink) Old 12-05-2010, 11:50 AM
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Anybody have any more info?

I am currently having the p2138 problem exactly as described. The local dealer says he has never heard of it. I have an 05 Outback XT. Has anyone had this successfully fixed?
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post #4 of 88 (permalink) Old 01-25-2011, 12:58 PM
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Same problem, same year, anyone have an update?

I have the exact same problem on the exact same year - 2005 subaru outback XT

The other day it happened when using cruise control which I thought was an interesting data point...

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post #5 of 88 (permalink) Old 02-22-2011, 12:53 PM
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In case anyone else checks this thread - I appear to have significantly reduced the occurance of this problem by seating the connect on the accelerator pedal assembly. I was looking for potential places were there could be a loose connection or frayed wire. I noticed that the plug had backed off a ways on the connector, so I pushed it back down.

Was happening 2-3x per week before doing this. Hasn't happened since doing this, and its been about 4 weeks.

I'm not saying I cured it for sure, only time will tell since it is intermittent.

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post #6 of 88 (permalink) Old 02-22-2011, 05:09 PM
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Thanks for posting your follow-up and, hopefully a solution.

The 2005+ fly-by-wire accelerator pedal actually has two sensors that track the position of the pedal, and two circuits going to the engine control module. The duplication is for safety -- both signals have to be within a fixed range (voltage) of each other. If they don't match, the ECM puts the engine into fail-safe mode.

The loose connector is a very strong possibility. It's also possible that in other cases, because the accelerator assembly is at floor level and could be exposed to water, salty solutions and dirt, the contacts themselves could get dirty or corroded, leading to bad connections which would also trigger the code.

Let us know if it does work out.
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post #7 of 88 (permalink) Old 02-28-2011, 11:17 AM
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I agree that it could have also been the pedal assembly given it's location and the fact that it doesn't look particularly sealed. I was going to replace that next if this connector reseating didn't work out. I'll post back if it reoccurs, otherwise it looks fixed for now, thank goodness.

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post #8 of 88 (permalink) Old 05-22-2011, 10:51 AM
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Dead Accelerator

I too had the same exact problem. The dealer claims no knowledge of the problem too-what a shocker. They ran my 2006 Outback for 3 days trying to get the problem to reoccur. It never did, but they finally replaced the APP Sensor/Pedal Assembly when they realized that I found it is a prevalent problem-from this website.
It cost me $100 deductible (as I had already purchased a very expensive extended warranty). I am going to try to get this back from Subaru myself. The dealer said he could not get them to reimburse me and they "could not" do it themselves. This is a safety-critical issue that needs to be addressed and Subaru needs to come-clean on it! I will do what I can to get them to do it. I hope it does hot happen to me again while I am doing 65 in the middle lane of a 6-lane highway. Did we really need drive-by-wire technology? Not happy about it in AZ.
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post #9 of 88 (permalink) Old 06-20-2011, 01:06 PM
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Please contact NHTSA

I too experienced this problem on 06/19/2011. My 2006 Outback has a service appointment on the 23rd of this month. Please report your problem with the NHTSA at 888-327-4236 or online at They compile statistics regarding dangerous defects and provide car owners with some level of protection when there are enough specific safety-related complaints. There are now only two complaints on file regarding accelerators that become unresponsive. My family was fortunate to have survived the circumstances surrounding our loss of throttle control and resulting deceleration. From my perspective this is a serious safety issue that Subaru really must address.
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post #10 of 88 (permalink) Old 10-02-2011, 02:18 PM
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Fixed Mine

Hi Everyone,

I've been dealing with this problem on my 2004 Outback for the past year. Cleaning and reseating the connector would fix the issue for a week or two, but the problem would always come back. I finally got sick of trying to fix the connector, so I cut it off and replaced it with some quick disconnect connectors from Radio Shack. (3 bags of 1/4" part #6403058). These new connectors have more "bite" into the metal tabs on the sending unit, so I'm hoping the issue won't come back. So far so good.

After I removed the original connector and took a closer look at it, I can see mine clearly has a manufacturing defect. There's an orange gasket around the edge of the connector, but on one side of the plug it is not aligned correctly. I believe this let condensation in and created a bad connection. Condensation makes sense based on the problems I saw, since they would usually happen first thing in the morning or anytime I put the AC on the floor setting.

For anyone else with this issue, you may be able to fix it my simply putting some grease around the edge of the connector and trying seal this gasket better.


Bad gasket

!!!!!!!!!!! UPDATE !!!!!!!!!!!!! - 1 week later and the problem was back. Apparently the radio shack connectors don't make good enough contact either.

Now I've soldered leads directly on to the sending unit connectors.

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