Just ran a Code P0156 Sensor Circuit Malfunction (Bank 2 Sensor 2) on my TB. Trying to educate myself on this 02 sensor thing, as I understand 4 different 02 sensors are on the 4.6 engine. Please advise me which and where this 02 sensor is located on this car. Can a rookie do this job, and is a special socket involved? Any help will be appreciated.
First you should diagnose the problem before taking off, much less
purchasing, any parts.
Simply because the code says Sensor Circuit Malfunction, it does not
imply that the sensor itself is the cause. It could very well be an open
or shorted wire to the sensor. What sort of voltage does the computer
report on that circuit, or if you don't have a full featured OBD-II
tool, what do you see when you backprobe the sensor circuit wires at the
If it's a heated O2 sensor, the heater supply connection(s) may also be
the culprit. It's usually a lot cheaper to fix a wiring problem external
to the sensor than it is to replace the entire sensor/pigtail assembly.
If you don't have a EVTM you're pretty much playing in the dark here.
I will hazard a guess that "bank 2 sensor 2" is the post-cat 02 sensor
on the car's right hand side (passenger side) but don't take my word
Mark, thanks for the reply. As you can probably tell, I am no mechanic,
just trying to save a trip to the dealer. My local Autozone ran the code.
What you say makes very good sense, but I do not have any way of testing
this 02 sensor. The Autozone readout states under hood, driver side, lower
engine area, above exhaust pipe flange, mounted in exhaust manifold. Sensor
located after catalytic converter, number two. Bit confusing to me, which
is why I went to this forum for advise.
A little googling shows I probably got this wrong, it appears bank 1
is on the right (passenger side, cylinders 1 2 3 4) and bank 2 is on the
left (driver's side, cylinders 5 6 7 8).
If you had the documentation (wiring diagrams, theory of system operation,
troubleshooting charts, etc.) and an understanding of how to make simple
electrical measurements, you could spend a mere $10 on a cheap digital
multimeter and make a reasonable attempt at properly diagnosing the root
cause of this code.
Without the necessary information and knowledge, you are forced into
attempting to do diagnosis by parts replacement, which is pretty
A buddy of mine and I easily diagnosed this exact same problem on an
Audi A6, it turned out the downstream O2 sensor had gotten its wiring
damaged when the exhaust system was disconnected during a clutch job.
The tool we used was a laptop computer with OBD-II software that allowed
us to monitor the signals coming out of the O2 sensors. From the readings
we were getting it was obvious what the exact problem was, and sure
enough when we got under the car you could see where the wiring had been
damaged once we knew where to look.
If you could borrow a laptop, you could probably spend about $100 for an
OBD-II interface and an accompanying program that would allow you to do
the same thing. You probably won't get out of a dealership for less
than $200 for an O2 sensor diagnosis and replacement.
Bank 1 is always the Right hand bank on a Ford product. (Bank 1 is the bank
containing the #1 spark plug). Bank 2 is the Left bank.
The #1 sensors are always before (upstream) the catalytic converters. These
ones responsible for fuel control.
The #2 sensors are always after (downstream) the converters. They have no
over the fuel mixture. All they do is monitor the efficiency of the converters.
Code P1156 means that there is an open or short in the O2 sensor feedback
(not the heater circuit)of the left upstream sensor.
Inspect the connector and vehicle wiring to the sensor. Also make sure the
is seated. If it is ok, the sensor is likely open. It's possible that there is a
problem with the wiring to the PCM from the sensor, but it's very unlikely.
OK guys will put this Thunderbird up on the ramps and see what I can come up
with. Will inspect the connector and wiring, but I am assuming this will be
OK. Reason being I am original owner of this car, so no one has replaced a
02 sensor. With this car being a garage queen, only 40,000 miles, pretty
much like new.
I cant, for some reason , come up with were TB stands for....
Offcourse , as everybody always keep asking, year, make , model ???????????/
If its a 4x4 the drivers rear O2 sensor wires sometimes get loose and are
chewed by the front drive shaft causing a circuit malfunction.
Maybe something to take a look at
Just ran a Code P0156 Sensor Circuit Malfunction (Bank 2 Sensor 2) on my TB.
Trying to educate myself on this 02 sensor thing, as I understand 4
different 02 sensors are on the 4.6 engine. Please advise me which and
where this 02 sensor is located on this car. Can a rookie do this job, and
is a special socket involved? Any help will be appreciated.
We are into one of those areas where the PC/ED is a little hazy..... The
list of possible causes is a little sparse and fails to include some
conditions that could set the code.
In the grand scheme of things, one could inspect the sensor and wiring for
anything obvious and then, if everything looks Kosher, replace the
downstream sensor as part of the diagnostic process.... One has to assign a
dollar value to their DIY diagnostic time to justify this.
In essence, this code indicates low output voltage from HO2-2.. the
downstream sensor on the passengers side. What we see is that there is a lot
of O2 in what's coming out of the cat.... this could mean that the Cat is
bad, it could mean that there is an exhaust leak.... it could mean a lot of
things. I have been the victim of customers saying "I didn't think that
mattered" too many times.... Without knowing anything else abot the car,
it's tough to form a reasonable reply.
Sidebar.... I chased one customer away several years ago.... His pick up had
developed one nasty habit or another (can't remember quite what it was) and
he refused to pay me to scan codes and data stream. His check engine light
had come on about a year earlier and still ran "pretty good". That, to him,
meant that this new problem had nothing to do with the check engine
light.... and these people are allowed to vote.....
At any rate.... if the original poster is bent on changing this sensor.. the
best tool I have so far found in a 7/8ths inch line wrench (providing you
can get it in to where you need.... ). The sensor is on the drivers side
after the cat.... they come out easier when things are hot....
If it was as simple as it looks, I'd be collecting welfare....
Now that you know which sensor it is you could swap it with the other
bank. You might just fix it by unplugging and plugging them in again in
the process(bad connection).If you get a code for the other bank you
know what it is for sure-the o2....If you get the same code you know its
wiring or slight possibility the ECM. Of coarse it is always good
practice to do what we call a "visual inspection" first :) Good luck.
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