My 99 TL has had a problem in that when driving, the car would suddenly hesitate (cut off) for a fraction of a second and the Immobilizer System dash lite with the "key" icon would flash on, then the car would start up again and the lite would go off. Recently the car wouldn't start at all for a few minutes, then later it started. It runs OK when it is running, but I think there may be a problem with the ignition key code and/or the sensor in the ignition switch that reads the key. I switched to my spare ignition key and the problem re-occurred, so I don't think it is the key itself.
I checked error codes and besides the EGR errors that I have had for months, it now has a P1706, which is related to the transmission gear selector switch. I don't see that the P1706 code has anything to do with the car stopping and the "key" lite coming on the dash. Can anyone tell me anything about this problem??
Charlie

 

It's probably the ignition switch, a well known pattern failure on these cars. Egr codes typically call for cleaning passages in the intake manifold.

 

Yes, I know about the EGR; I have replaced the EGR valve twice and removed the intake manifold and cleaned out all the gunk, but it still shows errors. The car runs fine, so I'm not worried about the EGR now. Thanks for the info on the switch; I will pursue that as the probably cause. I just hope it doesn't give out completely and strand the car somewhere before I get it fixed.