Can anyone tell me about these combined codes. I am getting both, and I have been told a thermostat or PCV valve!? I cannot verify either, any help??

 

P0171 is a lean fuel mix, usually caused by an intake air leak or an exhaust leak. check vacuum lines and intake air boots and tubing etc. P0597 is a fault with the thermostat heater control valve that regulates coolant going to the heater core. Check for wiring/connector issues then test to the pins of the valve but the unit may need to be replaced.. What year is the S60?

 

It is a 2015. The fault comes and goes.... I have gotten two diagnosis' and both are different?!? One says replace the thermostat, the other the PCV valve?? I am confused...

 

assume when you wrote P01710 you meant P0171 (p= powertrain and then there's a four digit code.) what source is telling you to replace the PCV? And when you say thermostat, that's not the same as the heater control valve. You have two different codes that appear unrelated (unless there's some underlying common wire/ground point). the P0171 is generated by the response signal from the MAF but points to a lean mixture.

 

Yes, P0171 code, I had Autozone do a scan, and it called out the PCV vale as a possible culprit. I took it to the shop on this island that does Volvo's warranty, recall work here. He got the P0597, and said I should probably think about replacing the thermostat? He indicated they were related. What the heck? This should not be that hard to figure out! I was an electronics tech in the Navy for ten years, I am good at troubleshooting.....but this is baffling!!

 

Do you know which engine you have (a VIN decoder will tell you the Bxxxx code or you can look for a sticker on the timing belt cover for something like B4204T11... I did find a bulletin (aka "Tech Journal") specific to tthe P0597 code https://static.nhtsa.gov/odi/tsbs/20...88748-5448.pdf but not sure if it applies to your car. It may be worth a call to a dealer as there's specific test process.

As to the P0171 code, its just saying the signal from the MAF shows the car as running lean. Typically its an air intake or exhaust leak, but it is possible the PCV can contribute if it has a component that is allowing air into the system. The PCV system has an oil separator system that takes the blow by gasses from the crank case, traps out the oil from the gasses (oil separators were referred to as the flame trap on older models), then allows the gasses to be recycled back into the intake. If a part fails you can get oil into the intake or it can clog and build up pressure in the crankcase leading to oil pushing out the seals or it can allow too much air into the intake (the engine's intake vacuum is used to suck in the blowby. At this point you'd need to do some tests to know if its an intake air leak (torn vacuum line/cracked hose/air tube etc) the oil separator, the PCV check valve etc.