Hello all,

I'm afraid this is my first post on this forum and not under great circumstances. I didn't do due diligence on this car (took the guys word on what codes it was throwing) and am now having a hell of a time. He passed emissions not 3000 miles ago with flying colors (I have the test to prove it), but now I am 6x over the NOX limit.

The current codes (and my best researched guess at what they are):

P1655: is an exhaust cam reset valve problem
P0445: Evaporative Emission System Purge Control Valve Circuit Shorted
P0448: Evaporative Emission System Vent Control Circuit Shorted
P0245: Turbo Wastegate A Solenoid Low
P0136: Rear Heated Oxygen Sensor Bank 1 sensor 2
P0031: Rear Heated Oxygen Sensor Bank 1 sensor 1
P0037: heated oxygen sensor H)2S heater control circuit low bank 1 sensor 2

I cleared everything once and those are what came back. Supposedly he went in for regular maintenance and threw a plugged cat code when he first bought the car but was told not to fix it due to "that probably isn't the issue". His wife drove it, and now it's where it is.

I have it schedule to go into the dealership Monday if I can't come up with anything. I'm certainly open to any thoughts or ideas about the correct course of action(s) in order to start working the many issues. Thanks in advance.

 

Car emissions testing is a balance between HCs (hydrocarbons indicating unburnt fuel - ie car running too rich) and NOXs - Nitrous Oxides get creating when the burn is too hot - ie the car is run too lean). Depending on your state test, they can measure at idle or at an elevated RPM - or even put your car under load (on a dyno). So you are looking for things that can create a lean mixture including vacuum leaks or worn out oxygen sensors.

These cars tend to cascade codes - ie one problem like a vacuum leak will show a list of faults like O2 sensors being out of range etc...(meaning they can't compensate for the leak).

I'd start with inspecting the vacuum lines and possibly get a smoke test done. Then you may want to check the evap purge valve for any issues with its vacuum tubes and possibly replace the valve. If no vacuum leaks are found, you may try replacing your rear 02 sensor if you don't know when it was last changed...

Last thought is to check electrical stuff - Make sure you don't have a low voltage issue (ie voltage regulator allowing volts to slip under 13 or so - try starting the car, turn on all your electric accessories - high beams, heater blower, rear defroster etc and see what voltage the alternator is putting to the battery terminals at idle). clean up any ground wire contacts etc if you can.

Also what year/model is this car?

 

That would be helpful wouldn't it. It's a 2000 Volvo V70 XC SE. And I appreciate your response. I'll start checking electrical connections.