Elizabeth Sanford

Hi all,

my husband has an 07 Chevy trailblazer that goes into what he calls “limp mode” after about a minute of driving. It only happens occasionally, but when it happens the car dings 3 times and a dashboard symbol of a check engine light with a down arrow lights up. Can anybody tell me what’s causing that to happen?

flyboy2610

I can't say exactly what the cause may be, but the most common cause is that the throttle body did not get the proper signal. These vehicles do not have a direct cable connection from the accelerator pedal to the throttle body. There is a sensor on the accelerator pedal and one on the throttle body. The accelerator pedal sends a signal to the PCM (powertrain control module) which then sends a signal to the throttle body. The throttle body then rotates a plates inside the throttle body which allows more fuel and air into the engine and you go faster. If that signal gets messed up the vehicle will go into limp mode as a safety feature to prevent the throttle body from going wide open, with potentially devastating results! Any of the three components could be the cause of the issue, or it could be the fan clutch. Yes, I said fan clutch. The fan clutch shares a 5 volt reference signal with the throttle body, and if the fan clutch is acting up or going bad, it can disrupt that reference signal, The PCM will interpret it as a throttle control issue, and the vehicle will go into limp mode. Limp mode issues can make you pull your hair out! My recommendation would be to take it to a good mechanic, preferably one specializing in automotive electrical work. They can hook it up to a live scanner, and while it's connected wiggle some wires to see if they can replicate the issue. I wish I could be more help, but as I said limp mode issues can be a real pain to track down, because so many different things can cause it. Good luck with it!