96 volvo 850 p0172 and p0141

casey38boost · Post by **casey38boost** » 21 Oct 2009, 00:42

Hi,

Looking for help with these two codes.

Originally had just a p0141 code for the rear o2 sensor heater.

Replaced rear o2 sensor, code po141 came back and now along with p0172.

Replacement o2 sensor was cheaper kind, not bosch.

Car also looks like it has had a recent cat converter replaced. I havn'et owned the car for long so don't know much history on it.

any idea on what could be causing these codes?

any help appreciated

Post by **Ozark Lee** » 21 Oct 2009, 09:05

Welcome to MVS,

The P0141 indicates a malfunction in the heater circuit for the heater in the O2 sensor is bad, it can be the sensor itself or the wiring to the sensor.

P0172 is normally triggered by either a vacuum leak or a dirty MAF sensor. The usual culprit if you have a turbo is the vacuum elbow on the end of the intake manifold, behind the alternator. It is very difficult to get to that elbow.

...Lee

casey38boost · Post by **casey38boost** » 21 Oct 2009, 17:37

i replaced the rear o2 sensor and these are the codes that came up again...

wiring looked ok.

I have a non turbo base model, but i will look for a vacuum leak.

I was going to try the front o2 sensor maybe that is it?

casey38boost · Post by **casey38boost** » 21 Oct 2009, 18:28

also i was thinking, maybe i am getting the code because i used a no name generic o2 sensor for the rear and not a bosch?

it was a direct fit, but alot cheaper then bosch.

thanks

Post by **jtp** » 21 Oct 2009, 19:13

I just got rid of po172 on an n/a 98 s70 after way too much time and money considering it was a 3$ vacuum elbow. This is how I found it: wait until the engine is cold, looking at the engine from the front of the car, place your hand to the left of the furthest left intake manifold pipe (passenger side), then reach back and down until you feel a vacuum tube that should connect to a nipple on the side of your intake manifold, the elbow connecting the nipple and the vacuum tube fails commonly and leads to po172. You might have to move your upper radiator hose to feel it and you will definitely need to remove the hose to fix it. Hope this helps.

casey38boost · Post by **casey38boost** » 22 Oct 2009, 07:39

ok, i will check into the elbows. thanks

FCPEURO · Post by **FCPEURO** » 22 Oct 2009, 08:33

The reason you are getting the O2 code again is because of the cheap O2 sensor. These cars are very sensitive and if you do not use the OEM parts, things like this will happen.

As for the P0172 code, you just have a vacuum leak you need to take care of. That one will not cost you much.

casey38boost · Post by **casey38boost** » 01 Nov 2009, 19:41

solved p0172 code, check vacuum hoses.

Replaced rear o2 sensor again with bosch direct fit, but po141 code still came back.

looked at wiring looks OK.

What would cause this code ? does anyone have factory service manuals with information on what might cause this?

Maybe a bad ecm or front o2 sensor causing this?

Post by **Ozark Lee** » 01 Nov 2009, 21:32

does anyone have factory service manuals with information on what might cause this?

This is for a '95 but it is 95% relevant to your '96. You don't have the OBD-I diagnostics like the '95 but otherwise it is all the same.

https://www.matthewsvolvosite.com/downlo ... vo_850.zip

...Lee

casey38boost · Post by **casey38boost** » 02 Nov 2009, 14:27

thanks for the info. I am going to look into it further, and the wiring diagrams for it.