Getting codes P0325 and P0420. Where to start?

What gasoline rating is the octane?

Hi Charlie,
Diagnostic Test Codes (DTCs) P0420 and P0430 ar "Catalyst Efficiency" codes. These simply mean that the catalytic converters in your vehicle are not performing the way they should be. To fix these codes, you will most likely have to replace the converters. However, these codes do NOT indicate why your engine wil not start. There are many things that can cause an engine to not start. Many of which may or may not set fault codes. You need to determine if the engine is getting fuel and ignition first then go from there.

http://www.obd-codes.com/p0420

TSB Number: 3316 NHTSA Number: 10017210 TSB Date: n/a Date Added to File: October 27, 2005 Failing Component:Electrical System Summary:Diagnostic trouble code P0420 may set on low mileage vehicles, or shortly after catalytic converter replacement
TSB Number: 3316 NHTSA Number: 10017210 TSB Date: n/a Date Added to File: October 27, 2005 Failing Component:Electrical System Summary:Diagnostic trouble code P0420 may set on low mileage vehicles, or shortly after catalytic converter replacement
there is a service bulletin for this.

http://www-odi.nhtsa.dot.gov/cars/problems/tsb/results.cfm?start=1&SearchType=DrillDown&type=VEHICLE&year=2005&make=CHEVROLET&model=COBALT&vehtype=PC&typenum=1&component_id=0&summary=true

Sounds like changing the belt had nothing to do with the problem unless something was disconnected or damaged. Maybe you already know all the problem codes, but if not here is a list of them. Also, when you make a reapair on one of the codes you have to reset the codes. They stay in memory until you rested them. So if you reset the 336 and 341 codes my disappear. Reseting the codes doesn't have anything to do with not starting. Make sure nothing was accidentaly disconnected or damaged. The throttle sensor is on the throttle which is in the housing that the air cleaner connectes with. I'm unsure where the Knock sensor is located. The catalyst sensor is probably one of the oxygen sensors in the exhaust pipes, the farthest away from the engine. Your discription of how the care died sounds to me like the throttle sensor.
The problem you have withour having someone check all these item with a system scanner, is you don't know which is defective or if they all are. When you purchase any of these sensors, they are expensive and they are not returnable once you open the packaging. If it not a connection or broken item that is ovbious, I recommend you have a quilified shop check the problem. Guessing can cost a lot for no reason.

P0122 Throttle/Pedal Position Sensor/Switch "A" Circuit Low Input
P0325 Knock Sensor #1 - Circuit Malfunction (Bank #1 or Single Sensor)
P0336 Crankshaft Position Sensor "A" Circuit Range/Performance
P0341 Camshaft Position Sensor Circuit Range/Performance
P0420 Catalyst System Efficiency Below Threshold (Bank #1)

Good luck

Thanks for using FixYa.

Gaker

You never replaced the exhaust converter,ruined by the
coolant--- PO420

The P1133 is probably an O2 Sensor also ruined
I would replace them all.

Who ever did the head gasket should have done
all that

Don't waste your money on anything that goes
into a fuel tank,not necessary,nor does it fix anything

re the funny smell, i need to speak to my friend as i have never heard of that one,does it smell of rotten eggs???

Code P0325 Knock sensor 1 circuit malfunction (bank 1 or single sensor)

CODE PO420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD BANK I * CODE PO325 KNOCK SENSOR NO.1 CIRCUIT MALFUNCTION BANK NO.1 OR SINGLE SENSOR

A P0325 refers to the knock sensor electrical circuit, not the sensor itself! So check all wiring & connectors leading to the sensor, back to the PCM. Good luck, I found a good P0325 article here - http://www.obd-codes.com/p0325

codes p0420 and p0430 are both post o2 sensors, the ones after the convertor, both sides if replacing