Can anybody explain to me what a egr solenoid is and what are the functions of a solenoid that is bad but doesnt throw a code?

 

Zim,

The EGR solenoid is actually a solenoid valve. The electrical part (solenoid) operates a mechanical part (valve) that switches manifold vacuum to the EGR valve on and off.

An EGR solenoid can fail electrically or mechanically. An electrical failure means the solenoid is inoperative and will usually set a trouble code, since the ECM senses an electrcal load out of range or not connected (incomplete circuit).

A mechanical failure means the solenoid is operating electrically but not switching vacuum. This won't set a code immediately, but will likely do so once the engine is operated at part throttle cruise (when the EGR is supposed to open) but the ECM will not detect the valve opening. Cruise along the highway at 55-70 for a bout ten minutes with no EGR and the trouble code should set.

The solenoid can be tested electrcally with a meter and mechanically with a vacuum gauge and pump. Inerting a jumper in the ALDL connector should energize the EGR solenoid. A vacuum pump connected to the valve port and a gauge on the other port should verify correct valve operation.

 

Thanks!