2006 nissan sentra se bypass?

Have a customer with a 2006 Nissan Sentra SE (pretty base model) remote start with keyless. I popped off the lower column and looked at the key cylinder and it didnt look like there was any kind of transponder/RF ring around it. I didnt use any bypass when I installed the system and it seemed to work fine but the cusomer has called me today, 3 weeks later, and told me the car starts and runs for 5secs then shuts off, I dont know if the tach is having an issue or what it is. There is no security light, didnt look like it had a cylinder ring, and keys dont look thick enough to have a chip in them, any help?

Yeah there is no immobilizer ring or RF Receiver on the cylinder, I guess Ill relearn the tach and see what happens...otherwise, I could go tachless?

this car does not have a immobilizer. only 07 and up. the only one that had it was some of the se-r's

Those have always worked well tachless for me. Not a single comeback. 0.8 or 1.0 seconds' crank time works well. What product have you installed, and where did you go for tach? I installed a Code Alarm on a 4-cylinder Altima, and the coil wires didn't work well for tach. I switched to an injector and it didn't come back after that.