Help! Just joined the site. Have found some excellent info! Thanks! I just acquired a 1998 S70, 137,000 miles, first Volvo. Had a couple of small issues was able to fix them (new thermostat, hoses, etc.). The check engine light just came on and the codes coming up are P0172 and P0455. Are these separate issues or are they connected? P0172, Emissions? P0455, Running rich? Any thoughts on fixing these would be appreciated...Thanks!

 

Cograts on the car. Emissions could be the air pump / check valve / controller. Rich may also be air pump. You also want to take a look at 02 sensors, cleaning MAF. Also make sure and inspect the vacuum tube that goes from the evap valve to to front vacuum intake on driver side of the intake manifold. If this is happening at low RPM- these are probable causes- If you replace 02 sensors and MAF make sure and use Bosch- Start with the vac hose as this is the cheapest. I had these same codes at low RPM- replaced SAS air pump (this sends air into the catalytic converter when you start the engine to get it into emission mode quickly) / check valve / controller / evap valve and tube / front and rear 02 sensors before all codes were cleared. Here's what my P0172 looked like:

1998 S70 no turbo

Freeze Frame Information:
1. DTC for which Freeze Frame was Stored - P0172.
2. Fuel System 1 Status - Closed Loop - Fault With At Least One Oxygen Sensor.
3. Fuel System 2 Status - Not Supported.
4. Calculated LOAD Value - 2.75 %.
5. Engine Coolant Temp - 210.20 °F.
6. Short Term Fuel Trim - Bank 1 - 6.25 %.
7. Long Term Fuel Trim - Bank 1 - -5.47 %.
8. Engine RPM - 840.00 Rpm.
9. Vehicle Speed Sensor - 0.00 Mph.