I stopped counting at eight times. '97 1500 5.2. My "Check Engine" light comes on when I go to the pub down the road. Not every time but it only comes on when I leave there. It does not come on anywhere else and this has been going on for six weeks. Three or four days a week I drive home 25 miles and stop at the pub for a beer, usually just one. I'm there for 20 - 30 minutes. The check engine light comes on when I leave the parking lot about one out of three times. Yes I believe in Karma but I think its more likely that there is some sort of EM source from a security system or automatic traffic light system producing RF noise and messing with the PCM. The code is P0301 and the truck is running fine and smooth getting an average of 14.8mpg to 15.5mpg. I have a wifi dongle on the OBD connector so I can just clear the code. It could be a problem with one of the sensors that only happens when the engine is started 20 to 30 minutes after being shut down but it isn't causing any problems and it ain't worth looking into unless it starts happening more often or the truck starts running poorly. For now, my truck has a sense of humor.

 

You're probably right with the EM field. It's probably just disrupting the spark in the wire, just enough to throw the code. It seems like it would take quite a bit of EM to cause that though. It the pub near an antenna tower?

 

Cell tower about 300 yards from the pub along with a sensing traffic light and a number of businesses that are closed with security systems. I find it humorously annoying at this point.

 

PCM uses the crank sensor to determine misfires, of course, the crank sensor is signal generator, so, the cell tower may be the interference causing the code to set, but, I would think it would set codes for more than just one cylinder......

 

P0301 Cylinder #1 Misfire
When was the last time the cap/rotor plugs where changed? My last job we had a cell tower in the parking lot(owner had an easement) i never had an issue with it.

 

I'm quite familiar with RF/EM noise as I was an electronic warfare technician in the USAF for 18 years on F111s. If there is a nearby signal source causing the problem, its most likely going to be because of a faulty pickup sensor, either the camshaft or the crankshaft sensor is compromised or, the buffer input circuit on the PCM has a signal gain problem. My whole ignition system is new but I did not replace the pickup sensors. Any RF emission is going to be a very small signal. It could actually be the result of two sources randomly hetrodyning but I like the explanation of it being Karma the best. Some kind of greater power in the universe is gently telling me that I should find another place to visit after work.