95 850glt rear O2 sensor question:

i have gotten the same code thrown several times for my 150000 miles
driven 850. the code is that the rear o2 sensor is not in correct
range basically. as you know these are kind of expensive and
non-returnable. is it the group's experience that the o2 sensor itself
is the problem, or could there the catalytic converter itself be the
more likely candidate? i am leaning towards the sensor, since afaik
the cat has experienced no adverse running conditions (flooded with
gas or a blown head gasket for instance) now if i decide to replace
the sensor, has anyone used a wire-in o2 sensor as opposed to the
direct plug in replacement? they are a good bit cheaper. thanks for
all the advice, i am tired of looking at the check engine light!
robbie

 

Do you know what the specific code number is? The system should be able to
tell the difference between a bad secondary O2 sensor and a bad catalytic
converter... whether it will tell you clearly which one it is is another
story.

But just playing the odds, I'd lean toward the catalytic converter. Just not
enough lean to tell you to spend your money yet! (Normally, front O2 sensors
give more trouble than rear sensors.)

Mike

 

the code given was 4-3-5-heated o2 sensor response slow

 

Yep - that is pretty sensor specific. Slow response is a common failure mode
for O2 sensors.

The wire-in type should work as well as the one with the connector. I've
used one (on a Nissan) and it was fairly easy. The one I bought didn't come
with splices so I had to supply those, but I think many come with splices
ready to go now. It just re-uses the connector from the original.

Mike

 

435: Heated Oxygen sensor (HO2S), Front Slow
If you have access to a scan tool monitor the front O2 Sensor as the
engine heats the voltage should go up & down I can not remember the
exact voltage I think it is the range 0.30 Volts to a high of 1.0 Volts
if it does not move or moves very slowly you need to replace the front
O2 Sensor Volvo sells a service kit that installs a cable in line you
might want to try this first before changing the front O2 Sensor
Glenn
Volvo Master Technician
ASE Certified Automotive Technician
--
"*-344-*Never Forgotten"
Is for the New York City Firemen who lost their lives on September 11,2001.
The official count is 343, but there was also a volunteer who lost his life
aiding in the initial rescue efforts. And I will never forget them as
long as I live,
nor should any American.

 

there are 2 sensors on the '95 850glt right? so the 435 code indicates
the front? just want to be sure b4 i spend any money. i thought the
front sensor in general on most vehicles was not heated b/c the engine
heated the exhaust manifold quickly enough so that the signal would be
accurate. Of course I am just learning here, so if someone can clear
that up it would be great. Or if Glenn could elaborate, it might clear
my head on it. Thanks!
robbie

 

My (layman) understanding is that the front O2 sensors are heated now (maybe
part of the OBD II requirements?) to bring the system into "closed loop"
operation as soon as possible.

Mike

 

The Front Heated O2 Sensor I am Looking @ the code Book as I type
HO2 Sensor = Heated Oxygen Sensor
Glenn

--
"*-344-*Never Forgotten"
Is for the New York City Firemen who lost their lives on September 11,2001.
The official count is 343, but there was also a volunteer who lost his life
aiding in the initial rescue efforts. And I will never forget them as
long as I live,
nor should any American.

 

On federal spec cars the O2 sensor has had a heating coil built in since
1984. The EPA reg at that time required the O2 sensor to be at operating
temperature in something like 45 seconds after start, well before closed
loop operation in something like two minutes after start.

Bob

 

Unless they are flat worn out most O2 sensor codes sre caused by vacuum
leaks. On '95 model 850s most notably be the rubber adaptor fitting in
the center of the giant welch plug at the end of the manifold just
behind and hidden by the power steering reservoir. Spray some gum cutter
or brake clean down the end of the intaske manifold with the motor
running and see if the idle speed changes. If it does hie thee to the
nearest Volvo dealer for a replacement fitting. You'll probably have to
remove the power steering pump to gain access, but it can be done
without removing the pump.

Bob

 

Thanks!

Mike

 

What you are describing always sets ECM232

--
"*-344-*Never Forgotten"
Is for the New York City Firemen who lost their lives on September 11,2001.
The official count is 343, but there was also a volunteer who lost his life
aiding in the initial rescue efforts. And I will never forget them as
long as I live,
nor should any American.

 

True, but 232 is almost always there anyway.

Bob

 

on fcpgroton.com their 1995 850 front 02 sensor shows 2 different
parts- 1 for cars with an air pump and w/o a pump- how do i tell if
mine has an air pump? thanks!