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OT - Volvo P0172 CEL ??

J

jCarroll

Well-known Member
Location
mid-Ohio
1996 Volvo 850 with 95,000 miles - it's our "bop around town" car.

Code means "System too rich". I've cleaned the MAF, and checked vacuum lines for breaks. After about 7 - 10 days the CEL light returns; run with it ON for a week, and there is just one code stored. Reset the code - have repeated this 4 times.

New O2 sensor runs from $40 for a generic sensor requiring wire splicing, to a Bosch for $200+ with a complete cable.

Assuming some potential for degraded MPG with a flakey O2 sensor, how much difference does it make? Or in other words, if I don't fix anything more, what's the downside?
 
You are on the right track. Having said that, I keep inheriting Volvo's from my in-laws and it is kind of a love/hate relationship. Had a '95 850 with the same code and ran it with the CEL on for years until I sold it. Just never found what was causing it. Currently have a '98 S70 (almost the same car) which just started throwing the same code. Have not popped the hood yet, but I am under the impression that most of these come down to vacuum issues on these cars. If you have not found it yet, verify that the vac. line leaving the engine on the passenger side, kind of behind the timing cover is not deteriorated. It is easily missed and is pretty notorious as a source of leaks.

Good Luck and let us know if you resolve it.

Kirk
 
If your O2 sensor is bad, the engine control computer will keep trying different mixture settings to try and correct it. Worst case it will make the car almost undrivable.
 
The code means that the system has too much fuel or not enough air. Big statement with alot of possibilities. If the fuel system has a return line, make sure it is not restricted. This will give to high of fuel pressure. Look for air restriction anywhere before the throttle body. Also a restricted catalytic converter may not be letting enough exhaust out and the computer thinks the system is rich. How is the power, if weak, remove the front o2 sensor and see if the car has more power. if so look at the catalytic converter.
 
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