1997 850 P0172 - Second 02 Sensor?

BlackThunder · Post by **BlackThunder** » 13 May 2014, 11:10

The front O2 sensor seems to be working but I am not getting any voltage or any read out on the second O2 Sensor and I got the P0172 error code. With the TORQUE App I was able to capture a couple of pictures:

I don't think the second O2 sensor has worked for a LONG time. So Should I go ahead and replace the second one to get ride of the CEL? Or should I start looking for vacuum leaks? I know they can also trigger this but I just had my car serviced and they didn't mention any vacuum leaks - also my vacuum pressure (via the TORQUE APP) is between 26 and 29 PSI - is that what it should be?

Current Fault Log
------------------
P0172: System too Rich (Bank 1)

Thanks, in advance.

Dustin

Post by **mecheng** » 13 May 2014, 12:02

That app looks really cool, do you pay for it? Can it be used with an iPhone?

I just fixed a P0172, it was the elbow near the intake manifold, I posted my results and fix.

Post by **erikv11** » 13 May 2014, 12:39

Rear O2 does not usually throw a p0172. I think I would first look carefully for and fix all vacuum leaks, especially at the elbow mecheng mentions.

BlackThunder · Post by **BlackThunder** » 13 May 2014, 16:18

@mechang There is a free version of Torque, I bought it since I didn't want the ads. There are IPhone versions. You still need to buy a bluetooth OBD2 adapter. I got an ELM327 off of eBay.

I'll check the elbow joints this weekend.

So I shouldn't think about replacing the secondary O2 sensor? The Torque app shows no voltage going to that sensor.

Dustin

Post by **misha** » 13 May 2014, 16:32

BlackThunder wrote:I'll check the elbow joints this weekend.
So I shouldn't think about replacing the secondary O2 sensor? The Torque app shows no voltage going to that sensor.

erikv11 wrote:Rear O2 does not usually throw a p0172. I think I would first look carefully for and fix all vacuum leaks, especially at the elbow mecheng mentions.

Smart phone live data aplications usually don't display valid data.I wouldn't trust it.

Post by **jblackburn** » 14 May 2014, 09:39

Rear O2 is not causing the P0172, and the voltage shouldn't show any swings unless the catalytic converter isn't working.

BlackThunder · Post by **BlackThunder** » 14 May 2014, 13:42

@jblackburn: So the rear 02 only works when the catalytic converter is NOT working?

I have no idea if the catalytic converter is working or not - how would I find that out?

My SAS air pump does NOT work - that is a different code anyway, right? I will check the elbow joints this weekend. Maybe something got knocked off when the car was at the shop 2 weeks ago (I had to get a new fuel pump relay).

I've been getting around 24 average high way MPG.

Dustin

Post by **erikv11** » 14 May 2014, 17:23

Tangential: PM me if you want to buy an air pump cheap, I have a low mileage one from an 850. I did SAS delete on my cars so I don't need it. And yes SAS issues throw different codes, not p0172.

AVIP · Post by **AVIP** » 15 May 2014, 10:42

You will know when a convertor is bad. My dodges went out and it would go over 2.5 rpm