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My 2009 Mustang GT, 44,000 miles, Manual transmission, sometimes goes into limp mode and the wrench light comes on. If I restart the car, it works again for a day or two until it happens again. Today it happened just as I entered a busy intersection, which felt very unsafe.

I have taken the car to a local mechanic and to a Ford dealership. Neither one could tell me what is wrong with the car since it did not happened while they drove the car and there are no codes in the computer.

Searching the internet, I find advice such as clean/replace Throttle body or Throttle Position Sensor, but why wouldn't the dealer do this if it was appropriate?

Do I have a better option other than driving a car that is unsafe? Can I even sell it in such condition and get a fair price?

Update I ended up buying a a code reader, but the issue never came back, despite daily driving. I am thinking the dealer must have done something that fixed the problem, as part of the $45 service, even though they claimed they could not find what was wrong with the car.

  • I had a 2004 Nissan Titan that went into limp a few times and did not set an error code.The problem was a component that Nissan called a IPDM - intelligent power distribution module. It was a relay that all ? power , except the starter, went through. They replaced it under warrentee so I don't know the cost. – blacksmith37 Feb 1 '18 at 16:11
  • I'm guessing this is an AT? If the wrench light is coming on it's probably a transmission problem and the most you'd see out of the generic OBD2 side would be a p0700. You really need to leave the car with someone who can drive it for an extended period of time and catch the fault as it happens. – Ben Feb 1 '18 at 22:05
  • This is a manual transmission car. – IKnowNothing Feb 2 '18 at 18:04
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If your car went into limp mode there should be On-Board Diagnostic (OBD2) codes stating what the problem was. It's hard to imagine a dealer being unable to figure out what is wrong. If there's no code then the computer itself could possibly be at fault, in which case they should figure it out.

You need to get this problem fixed for your own peace of mind, and if you want to sell it you'll need to resolve it or you will not get decent money for the car as anyone buying it would be taking a big risk. I suggest you get a bluetooth OBD2 dongle and read your codes yourself. You can pair the dongle with just about any phone or tablet with free OBD software and it will constantly read your car's diagnostics data, any codes that come up will be captured as well as sensor data which can be used to determine what is wrong. Once it goes into limp mode you can save it all and show it to a good mechanic to figure out what the issue is. If it doesn't produce a code that in itself is important.

  • It sounds like the OP erased whatever codes there might have been in order to get it out of limp mode. You're right about getting a cheap Bluetooth ELM327 device. Can pick one up cheap on eBay or Amazon. Chinesium imports and all. – Pᴀᴜʟsᴛᴇʀ2 Feb 1 '18 at 19:59
  • You'd think that codes from issues like that would be held in non-volatile memory so you could see them later! – GdD Feb 2 '18 at 11:49
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    Maybe I should drive in circles on the dealer parking lot until it happens again. – IKnowNothing Feb 2 '18 at 18:06
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I had that happen to me, turned out to be the the alternator. Check your alternator output to make sure it's not overcharging, ECU's are sensitive to voltage, mine would go into the limp mode when it saw too much voltage and it would not throw any error codes.

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