1996 850 - OBDII scanner showing front O2 sensor only?

Volvo Tank · Post by **Volvo Tank** » 10 Feb 2015, 06:37

I hooked up my scanner, and for some reason it is pulling live data but only registering the front oxygen sensor only....

Here is the output:

FUELSYS1 CL_Fault
O2S B1S1--- B2S----
O2B1S1(V) 0.740 ?
SHRTFTB1S1(%) 1.6

Any ideas? Is the CL_Fault due to the other O2 sensor not being found? Wouldn't that throw a code?

Post by **Ozark Lee** » 10 Feb 2015, 06:52

There are some scanners that can't seem to get to the rear sensor. Is your check engine light on?

...Lee

Volvo Tank · Post by **Volvo Tank** » 10 Feb 2015, 07:04

CEL is not on...if that's the case then I guess it's probably safe to assume it can't read it?

That sucks...I have a sneaking suspicion it needs to be replaced, but it sounds like there isn't a real easy way to do that now

Post by **Ozark Lee** » 10 Feb 2015, 07:17

If the ECU couldn't see it then there would be a CEL for sure so I think we can assume it is functioning. The rear sensor really doesn't do anything in terms of performance. The rear sensor's function in life is to monitor the efficiency of the catalytic converter but all of the mixture calculations are based on the front sensor reading.

...Lee

Volvo Tank · Post by **Volvo Tank** » 10 Feb 2015, 14:03

Got it...thank you for the help!

Post by **matthew1** » 10 Feb 2015, 16:16

Often the front O2 sensor will be dying for months before setting a code. Fuel economy drops.

Volvo Tank · Post by **Volvo Tank** » 10 Feb 2015, 17:44

That is good to know, since that is exactly what happened. Figured it may be the rear since it wasn't registering