First the sensors on the exhaust manifold or before the cat converters are heated oxygen sensors ( not O2 sensors but HO2S sensors)
there are O2 sensors after each cat converter before any muffler
Testimonial: "They are unheated according to my Ford dealer by using my vin#.Two sensors front bank and two sensors rear bank.My question still remains.Are there any sensors at the third cat converter located at the resonator/muffler ?"
something you can check for your self
if the front exhaust manifold sensors have 4 wires they are heated , if only 2 they are o2 sensors
are you sure that there is a cat converter at the muffler as the one at the front would be doing the job and any others would be converting nothing
the first sensor (HO2S) is used to examine the exhaust composition and report to the ECM so that the air/fuel mixture can be adjusted
the cat converter lights up and burns off the gasses and the O2 sensor reads what is left and also reports to the ECM to fine tune
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SOURCE: Code P0141. O2 Sensor heater circuit fault (Bank1,
It is probably the sensor before the cat. if it has a heater. The heater circuit going bad is a common problem, it does not affect the way the car runs after it warms up, it is an emission device to heat the O2 sensor up quicker than the hot exhaust gas would. It should be replaced because it will keep your check engine light on and you would not be able to pass an emission test.
SOURCE: location of the bank 1 sensor 2 O2 sensor on a 2001 ford escape
B1 means the sensor is located on the same bank of the engine that has the #1 cylinder. B2 is located on the opposite bank.
S1 means the sensor is located BEFORE the catalytic converter
S2 means the sensor is located AFTER the catalytic converter
You didn't say which engine you have, so I've included the diagrams of both 4 cyl and 6 cyl so you can see the banks
SOURCE: PO420 code-service engine light is on
also check the cat by removing the o2 sensor befor the cat and look in the hole. if there is any deformity to the cat ( melted, holes, missing) replace it right away the nature of the 2.5l it sucks the cat matirial back into the motor damaging the rings and bearings. the most comon cause of cat failure on that modle is head gasket failure so before sinking 750$ in a cat have the head gasket checked.
SOURCE: I have 2004 ford escape
p2195
02 sensor signal stuck lean bank 1, sensor 1
p2197
o2 sensor signal stuck lean bank 2, sensor1
i beleave this will be the sensor before the catalytic converter
SOURCE: 03 ford escape, how hard is it to change the
Regards,
Tony
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