I have a 2002 L300 and sometimes will not start. scanned for codes......PO727 and PO1780 came up. replaced pnp switch, it was faulty. now code PO1780 is gone, but PO727 came back and it still has intermittent no start. cranks but no start, has fuel and air delivery is ok. according to my charts (mitchellondemand). ecm may have an issue, but i am leaning toward the vehicle speed sensor. can someone help point me in the right direction? also erratic idle sometimes on startup??? i am stumped............please help!
matthew

 

Used to workin on older cars, Mercedes, and airplanes, but I'll give it a shot.

Does your car only have trouble starting when its warm? (Starts fine in morning, but then drive to store and won't start when you come out?)?

If so, you first stop would be a CPS (Crankshaft Position Sensor). I'm not sure that GM calls it that, but the sensor that detects crank position. It could also cause small stumble at idle, but I would clean my MAF (Mass Airflow Sensor) for that.

Im not sure what this PNP you speak of is...
Let me know if this helps.

John

 

Got it. Park-Neutral- Position swich.
Good that u changed it if coded, but not likely causing current problem.