2005 equinox with P0405 code.

• egr valve
• egr sensor
• cam shaft sensor
• barometric pressure sensor (map sensor)

vacuum leak somewhere, out of time, broken timing belt or missing teeth.

code p0405 refers to exhaust gas recirculation(EGR) valve position sensor A-low output.--- causes --wiring shorted to ground--EGR valve position sensor--- ECM would go for the EGR sensor. Use only genuine parts as after market are not always compatible with CPU in the car.

You need to diagnose the EGR System
Not replace parts in hope of getting it right
Codes only indicate an Emissions Malfunction
or Fault, thus the code
Codes & trouble charts are used to then component test
Google the code & study the problem
There are many EGR Codes--- study yours ,as it pertains
to your vehicle & engine package
Try You Tube Video-- to get a basic of what egr system is & does

P0405 means Exhaust Gas Recirculation Sensor A Circuit Low. It may caused by Short to ground in EGR signal or Reference circuits or voltage in EGR ground or signal circuits;Bad EGR valve; or Bad PCM wiring issues due to chafing or loose terminals.
P0300 is Random/Multiple Cylinder Misfire Detected. It may be something wrong with spark plugs or wires,coil,oxygen sensor,fuel injector,etc.
As for P2670, it seems for the Actuator Supply Voltage "B" Circuit Low.

greetings

P0108....Manifold Absolute Pressure/Barometric Pressure Circuit High Input

P0300....Random/Multiple Cylinder Misfire Detected

P0400....Exhaust Gas Recirculation Flow

P0433....Heated Catalyst Efficiency Below Threshold (Bank 2)

Do not have a listing for the 0068 reading as it doesnt exist in my list ,looking at this i would block off the EGR valve with a nice home made coca cola can gasket and this should cure your problems

CODE PO134 - HO2S 11 BANK 1 SENSOR 1 INSUFFICIENT ACTIVITY CONDITIONS. CODE PO403 - EGR SOLENOID CONTROL CIRCUIT MALFUNCTION. CODE PO405 - EGR POSITION SENSOR CIRCUIT LOW INPUT CONDITIONS. PROBLEM COULD BE THE EGR SOLENOID OR EGR POSITION SENSOR.

P0405 - Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage

You may have to replace the EGR sensor, but remove it and clean it up good to try it again first. Sometimes the pipe feeding exhaust gas up to them gets plugged.

P0405-egr Position Sensor Circuit Low
check the wires at the sensor connector for loose connection,and corrosion.read voltage with volt meter,check ground wire to ensure good ground connection.If all is ok,replace part.

Erase the code and see if it returns. If it does, replace the valve. What engine do you have? If it is a 3.4 it should be right on top. One plug and two bolts.