I have a 2002 GMC Yukon XL SLT 4x4 Flex-Fuel. When the outside temperature drops below 10 degrees Fahrenheit (I live in Michigan), the car won’t start. It turns over strong (no battery problems) but it won’t produce spark to the spark plugs. My mechanic tried all the obvious things and narrowed it down to the main engine computer (so he thought). I went ahead and bought a brand new one, had it programmed at a GMC dealer and installed there. No change. No spark under 10 F. Do I need to move to Florida? Any suggestions?
Has anyone checked the output signal from the crankshaft position sensor when this no-start occurs?
These sensors can become sensitive to temperature to where they fail to function. And if there’s no signal from the CPS, there will be no spark from the ignition.
Thanks, I will have my mechanic check that. This problem has had me arrive late for work too many times.
I like Tester’s CPS theory. But my reason for posting is to try and point out the irony of a vehicle named “Yukon” having trouble with cold weather (which perhaps everyone has already seen, but I’m a little slow, eh?)
Well, I just changed the crankshaft position sensor for a new one. The beast still won’t start. However, the mechanic found a small vacuum leak above cylinder 3. It will occasionally register a misfire. But he doesn’t see a connection to having no spark sent to all spark plugs if the ouside temperature falls below 14 F. I’m ready to trade this thing in. Any more good advice?
Yeah, get a reliable car! (ie: low cost and simple), maybe a manual transmission would be beneficial in your situation, besides, jobs are hard to come by up there, so if ya got one that’s payin’ ya enough for a Yukon…
Are you sure there’s no spark? Because a lack of fuel would cause the same thing. It may be possible that wires going to the fuel pump are slightly loose, and when it’s cold, the wires are loose enough to not run the fuel pump, hence no start.
You’ll go broke if you just keep throwing parts at it. You need a definitive diagnosis. Even though the “check Engine” light may not have come on, there may be stored error codes. Has it been scanned? Has it been definitely established that there is no spark? A WAG is that some electrical connector is loose and loses all contact when is contracts in the cold.