Limp Home Mode?
 

2010 3.6L CTS automatic. I can pull the gear selector back beyond drive. When this happens, the gear position display D goes from red to white. The transmission shifts normally, but the cruise control does not function. I mention the cruise because on 3 occasions, the idle increased to the point the speed will get to about 48 MPH. If I stop, once I accelerate to 20 MPH, I can take my foot off the gas and the speed increases and the tranny goes through the gears up to 6. If I just slow down with the brake, the speed will increase as soon as the brake is released. I am going to schedule warranty service to prevent the gear selector from going that far back, but is this some kind of limp home function?

Hi OscarNelson,

I can see where your CTS behaving like this would be concerning. I checked the owner’s manual for any way to initiate a “limp mode” in the manner you describe and did not see anything. I would be happy to contact the dealership on your behalf to schedule an appointment an express your concerns, if you would like. You can PM me your VIN, mileage, dealership, and contact information, and I can get this process started.

Have a great day,

Austin J.
Cadillac Customer Care

Bringing it in to dealer on Tuesday. My service rep wants me to take a tech out for a test drive to try to reproduce the 1400 rpm idle as that seems to be the crux of the biscuit, not the 48 MPH speed.

Good Afternoon OscarNelson,

I am happy to hear that your dealership is assisting you with taking the proper steps in order to get this matter addressed. Please keep us updated on how your service visit goes on Tuesday.

Kind regards,

Jonathan A. (Assisting Austin)
Cadillac Customer Care

Apparently, when the shifter was replaced for a previous fault, the nut holding the control linkage was not properly torqued. The condition deteriorated to the point that every time you pulled the shifter all the way back, the engine idle would change. When I got off the freeway going to the dealer, I pulled the gear selector back and got a false neutral!

Adjusting the shift control linkage, which was at the far end of its range at this point, fixed all problems. I talked to the tech who did this adjustment and he said there were no error codes stored anywhere. Why the engine control was affected by the tranny being shifted to a position beyond normal will remain a mystery, unless someone at GM reproduces this condition (very easily done) at a development facility.

Bottom line is that if your linkage gets out of adjustment, the transmission may act normally, but the engine may not causing the car to accelerate. Not at a rate that could not be quickly overcome with the brakes, but disconcerting at the least. The first sign of this problem in my case was when going from Park to Reverse, the lock button did not pop out until the selector was pulled further rearward. Electronics are a great aid, but keep your head out of your keester at all times.