Problem With 2004 Legacy Wagon Neutral Safety Switch

[Dawnmarie86]

I have a 2004 Legacy wagon, 2.5L 4 cyl,  and I am having problems with the neutral safety switch. I have replaced it twice and the check engine light will still come back on and read a code stating that it is the neutral safety switch.

 

Every now and then my car won't start and I have to turn on the key, pull the gear shift down and back up, turn off the key and repeat a couple times before the car will start.

 

Has anyone else had this problem? How can I fix it?

 

Thanks.

[Fairtax4me]

It would be more helpful to give us the actual code so we can look up Subarus Definition of the code and their diagnosis process.

 

Automatic transmission, or manual?

[Dawnmarie86]

It is code P0851. The code first began by reading P0851- Neutral Safety Switch. But since I replaced the starter relay it now reads P0851- Neutral Switch--Low Input. My car is an automatic.

Edited April 14, 2014 by Dawnmarie86

[Fairtax4me]

Basically, there is a set of contacts in the Nuetral safety switch on the side of the trans that send a a signal to the ECM when the switch is in either Park or Nuetral, when the key is turned to start. Corrosion in the Nuetral switch or in the terminals in the nuetral switch connector can cause enough drop in voltage across the contacts that the ECM does not get the signal when the key is turned. This can also cause starting problems since the same contacts also send voltage to the starter solenoid. Low voltage there could cause the solenoid not to engage.

 

There is also a large 12 pin connector that the voltage must pass through while on its way to and from the Nuetral switch. If you follow the wires from the Nuetral switch up the side of the trans you will find the other connector.

 

Check inside both connectors for any sign of dirt or corrosion before replacing the Nuetral switch. Sometimes just unplugging the connectors and reconnecting them will remove light oxidation from between the terminals and restore normal conductivity. If cleaning and reconnecting the two connectors does not fix the problem then you should replace the nuetral switch. There could still be a wire issue that will need more specific testing, but wire issues are not common in these cars.