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I have a Pontiac G6 with an automatic v6 engine. Lately when I want to go above 70mph, the engine needs to rev at almost 5,000 RPM's, which seems high. I used to use cruise control every day but it hasn't been working lately either.

Could these be related, or is one causing the other?

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  • What is the RPMs just below 70, say at 55 or 65? Before it goes balistic ...
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Sep 28, 2016 at 0:30
  • Is the check engine light on? Does it shift through all the gears sequential as speed increases.
    – Fred Wilson
    Commented Sep 28, 2016 at 3:13
  • Any chance "overdrive" is on?
    – tlhIngan
    Commented Sep 28, 2016 at 3:55
  • @Pᴀᴜʟsᴛᴇʀ2 approximately 3-4K
    – munale
    Commented Sep 28, 2016 at 3:55
  • @FredWilson check engine light is on but it has been for a while. I feel like it's only shifting like twice
    – munale
    Commented Sep 28, 2016 at 3:56

1 Answer 1

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Based on your replies to comments, here's the diagnosis: Most likely, you tripped the overdrive. Most modern cars have this, and most people don't know about it. Look at 2 things:

  • look at your shifter, there should be a second button under the shifter button. That's the button that activates and deactivates the overdrive.
  • Look at your dash, there should be a light on somewhere, probably amber in colour, indicating the overdrive is activated.

What the overdrive is, really, is it either allows or prevents the car from shifting into high gear. Shifting into high gear saves gas, preventing a shift into high gear keeps you on a better gear ratio and in higher RPMs, therefore in a better powerband.

Some model years of the G6 only had a 4-speed automatic, therefore disabling the overdrive will leave you with 3 gears:

  • that's why it's only shifting twice (1st, 2nd then 3rd)
  • that's why the RPMs are over 5,000, you are doing 70 mph in 3rd gear!
  • and that's why the cruise control isn't working, it's not supposed to be functioning with the overdrive off

Click that button once and see if the car goes back to normal. :)

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  • I checked and there doesn't appear to be an overdrive button. It does have a separate gear for 3
    – munale
    Commented Sep 28, 2016 at 12:47
  • 2
    Get your trouble codes read, it may be a shift solenoid that's gone bad.
    – tlhIngan
    Commented Sep 28, 2016 at 18:33
  • @munale - When you say there's a separate indicator for "3", you are saying this is just below the "D" on the selector? D will allow it to go into overdrive. 3 will keep it in that gear. You really need to get the codes read. I'd bet you are in some sort of Limp Home Mode.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Sep 28, 2016 at 19:59
  • Yeah it's P R N D 3 L with no discernible overdrive button. Can I get codes read anywhere?
    – munale
    Commented Sep 28, 2016 at 20:02
  • @munale - If you are in the States, you can take your car to almost any major chain parts store (O'Reilly's, AutoZone, Checker Auto, etc.) and they'll read them for you. Make sure you write them down. I'm still betting this is an issue where your car is in limp home mode.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Sep 28, 2016 at 22:05

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