Throttle body acting up, but replacing it doesn't help

Hi there! My Vibe has been having a throttle body issue for a while now. Chief symptoms: it would rev at about 2k-3k in idle, and sometimes it would idle at about 500rpm, and stall out. Initially, it was throwing P0505 and P2111 (as well as P0136, which the mechanic said was unrelated, and which he did not try to fix at my request, because he wanted an absolute mint to change the sensor). The mechanic replaced the throttle body, and the codes were cleared.

For about a month, everything was fine. The symptoms began returning, but intermittently. The check engine light would come on, then disappear. On, off, symptoms, no symptoms. Nearly a year passed as I monitored the issue. The check engine codes were P0121, P0136, P0138, P2103. Eventually I took it back. The mechanic said very briefly, oh yeah, this is a bad throttle body. He changed it out again.

Well, for about a month it was as smooth as anything. Symptoms are back. Current error codes are P2111, P0505, P0136. As before, the issue is intermittent, and the check engine light will be on for a week, then off for a week.

I’m getting a little weary of the guy playing musical chairs with the throttle body. Is he barking up the wrong tree? Is the O2 sensor fault somehow causing the throttle body issues (throttle body is getting stuck, it seems like)? I’m going to take the car back to the guy and ask about it, but assuming he says ope, let’s change the throttle body again…well, is there a different approach we might want to take here?

My first thought after reading this is that you need a better mechanic. My second thought is that this car has damaged or corroded wiring but I can’t go any deeper because you didn’t tell me anything about the car except it being a Pontiac Vibe and the code history. No year, mileage, or condition.

Thanks for the reply! My first thought is: yeah, you’re right. I absolutely do. But I’m in the irritating position where the guy who is not good has to fix his own mistake for free.
Sorry regarding the detail…2006, 170k miles, two careful owners. No major issues during ownership besides a gearbox (manual) replacement a few years ago. Is there anything particular regarding its condition that might be important for this issue?

Yes, 16 years old… corrosion. Yes, 170K miles…vibration wearing away wire insulation, YES, trans replacement that damaged wires from stress or not being replaced into the holders as carefully. So ALL are important things I’d like to know if I am trying to fix the car!

Now you said the throttle body has been replaced twice…but what about the idle air control (IAC) valve? The P0505 code is likely a bad IAC

As for the P2111…These are the causes;

  • Faulty throttle body… replaced twice so not so likely
  • Dirty throttle plate or linkage
  • Faulty throttle position sensor
  • Defective accelerator pedal position sensor
  • Throttle actuator control motor is defective
  • Corroded or damaged connector
  • Faulty or damaged wiring Faulty PCM

So the mechanic fixes his own mistakes for free but uses your time and travel to do it. You have to determine the time to cut the mechanic loose and pay to get the car fixed properly.


This is really great advice, thanks. Going through your list I had a couple of questions:

Again, thanks for your help. I am planning on ditching this particular mechanic and going for a different guy. But I’m trying to educate myself on what the issue might be here so that I have something to tell the next guy–what’s been tried up until now, etc.

Suggest to read through the following topic as well.

If your Vibe is configured similar to that car above (GMC Canyon I think), the sensor is part of the throttle body and cannot be replaced independently. In any event most likely there’s a sensor in the throttle body that connects to the ecm, which allows the ecm to determine the throttle valve angle (how much it is opened), say from 0% to 100%. Since replacing the throttle body didn’t do the trick, next step, somehow your shop has to be able to compare the actual throttle valve angle (perhaps by a visual inspection) to what the sensor is telling the ecm. My guess, something wrong w/the electrical connection between the sensor & the ECM. If any ground wires have been disturbed between the engine/cylinder head and the chassis, consider that a prime suspect.

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Looking at Rockauto I see what is clearly a drive by wire throttle body but I also see a TPS and IACs for sale. Normally the throttle body would contain all 3 but I can’t see your engine and I can see Rockauto. The IAC looks like a stand-alone part with 2 hose ports. The TPS looks normal, 2 screw mounting, sensor.

And yes, cleaning the throttle body would be a normal service with this problem.

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This car, and its sister Toyota Matrix, came with two engine options.
The basic 1zzfe with a 6300 redline and 5-speed manual trans, or the 2zzge with 8200 redline and 6-speed manual trans.
The 1zz is drive-by-wire; the 2zz has a throttle cable and IACV.

Hope that clears things up a bit.


Again, that is why ALL the car info is important! So which engine do you have?

The Pontiac only came with the 1.8 liter engine that year.

The fault codes relate to electronic throttle control, would not be the 2ZZ-GE engine with cable control.

I’ve got the five speed! I have no objection to sharing more info, I’m just not really aware of what information is relevant.

So, if I’m correctly understanding your comments above: there are several different systems that might cause this error to be thrown, and nobody here thinks that replacing the throttle body a fourth time will be the smartest thing to do. I ought to take this to a mechanic who’ll take the time to properly diagnose this. Is that about the long and short of it?

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Yes …


Thanks for your input, all. I’ll swing by here when I eventually get it sorted to report on what was, in fact, wrong with it.

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For poster’s asking questions here about car symptoms, to serve yourself best, provide

  • make/model
  • year
  • odometer miles
  • engine displacement
  • engine code (found on a sticker on the underside of the hood usually)
  • transmission type (manual, automatic, cvt)
  • pertinent non-stock modifications
  • any recent work done prior to symptom developing

Concur, not much point in replacing throttle body again. Ask friends, co-workers etc which independent repair shop they use for their cars, choose one that has Pontiac or at least GM experience, make an appointment. hmm … If I had this particular problem, and I had proved grounding wasn’t the problem, and my checking account was properly flush, I’d probably give the local dealership shop the first go. May require a special scan tool.

So it’s a throttle by wire vehicle? The wiring going to the throttle control motor and position sensor is probably the issue. The fact that a new throttle body fixed it for a while indicates that the problem is with the electrical connections to the throttle body or the wiring close by.

Drive by wire would suggest that the steering is done electronically and the steering wheel is just an electronic control! Maybe some day we’ll see such insanity.

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The OP’s car is mechanically identical to a Toyota Matrix, and–to the best of my recollection–it uses all Toyota components.

Of course looking for a repair shop that has Pontiac experience is silly since Pontiac closed in 2010 . We have a vehicle repair shop here in town and they repair almost any brand you can think of .

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I believe your OP is the link in post number 6 of this thread, above. Suggest you place your update there too, for others who may find it during a forum search.

Your new mechanic seems to be very much on top of the situation. Flooded cars can present really difficult to diagnose problems according to reports we get here. With the knowledge of prior flood history, a car owner might wonder if being more proactive than just fixing things as the crop up would be worthwhile; e.g. asking a shop to do visual inspection of all connectors, replacing any that are corroded. I’m not sure however that this is the best strategy, given the “leaving well enough alone” adage. I expect I’d be inclined to just address the problems as they occurred. Perhaps other posters here will have an opinion.