I have a 09 chevy hhr with a po340 code and jerky motions as well as jerky rpms. I have replaced the cam pos sensor and the issue remains. any suggestions would be very appreciated.

 

First read this link OBD-II Trouble Code: P0340 Camshaft Position Sensor Circuit Malfunction.

A fairly common thing is the wiring harness has fallen onto the exhaust or gotten chafed somewhere. Also the connector from the harness to the ECM sometimes get banged up, disconnect it apply some di-eletric grease and reassemble after checking the pins.

 

before I short out the whole system, where would I find the ECM and should I remove the pos terminal before unplugging?

 

It is the module under the Darth Vader hood in front of the fuse box where the main wiring harness terminates.

Probably a good idea to disconnect the NEGATIVE battery cable, unless you like tempting the fire department.

Just to be sure; you replaced the Camshaft Position SENSOR, not one or more Camshaft Solenoids, right?

Also the link I provided says to not rule out a Crankshaft Position Sensor.

 

Try the search tool at the top of the page - look for "ecm location" - there is a thread detailing the locating all the different "computers".

(tip: it's just in front of the under hood fuse box).

No, do not remove the Pos terminal - damn man, that is dangerous if you cause a short with your wrench. Disconnect the NEGATIVE terminal at the battery.