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Q: Car suddenly went into limp mode

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After some off-roading last friday, the car suddenly went into in limp mode, doesn't go faster than 40Km/h with the pedal to the metal and makes awful sounds. I don't know if it's related but have recently changed brake pads and brake sensor switch, transmission oil

My car has 157000 miles.
My car has an automatic transmission.

Hello and thank you for contacting Your Mechanic. Your Hummer could have the brake system engaged for the traction control. Disable the traction control and see if the engine will increase in speed.

Another thing to check is the parking brake cable. See if the cable is snagged on anything causing the vehicle to have a dragging resistance in the brakes. If the brakes are free and working correctly and if the engine continues to be in limp mode, then there could be an issue with the transmission.

Check all of the harness connections to all of the sensors on the transmission and transfer case. If all of the connections are tight, then I recommend having a professional, such as one from YourMechanic, drive your Hummer and determine why your car isn’t getting enough power and is making unusual noises.

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