My daughters 2004 jeep grand cherokee failed emissions. codes were 2 lower o2 sensors and 1 upper. but i noticed fuse in engine was blown, replaced fuse, and blows again. disconected all 4 sensors, fuse still blows. i've looked at wiring and no areas where wires are bad. any ideas ???

Hi Amanda , I want to help you with your question, but I need more information from you. Can you please add details in the comment box?
USA car or NOT? USA is WJ jeep gas engines.
sensor B2S1 is bad. or worse.
or wires to it burned up , clamps bad and wires hit red hot
exhaust pipe
no engine told 4.0L i6 or 4.7L v8
must be v8. bank 2.

the front sensor is bad (aka upstream)
bank 2 is not cylinder 1 bank.
on USA car , bank2, seated in driver side
is right bank of engine is 2.
facing said engine is left bank.2.
the sensor is here

in the USA there are 2 v8 smog parts, CALF or FED

seen here clearly in the service manual oem I have in hand



the 4.0 liter is very trick this year,
it has an odd splite exh manifold
but only seen on calif engines,
see next photo for 4.0L engine,

Some are easy fixes (O2 sensor), the fuel vapour ones need a bit of investigation, as does the Neutral Safety Switch..

P0135 JEEP Code - O2 Sensor Heater Circuit Malfunction ...

https://www.engine-codes.com > p0135_jeep
'P0135 JEEP code possible causes · Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 · Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit fuse · Heated Oxygen ...

P0455 JEEP Code EVAP System Large Leak (With Video)

https://www.autocodes.com > p0455_jeep
May 30, 2020 - 'P0455 JEEP code tech notes ... The P0455 it's very common code because the code is set if the gas cap is loose or missing. Start by tightening ...

P0442 JEEP Code Evaporative Emission Control Small Leak ...

https://www.autocodes.com > p0442_jeep
May 30, 2020 - The P0442 code means that the control module has detected a small leak in the Evaporative Emission (EVAP). Loose fuel tank filler cap is the ...

P1899 JEEP Code - Park/Neutral Switch Circuit Conditions

https://www.engine-codes.com > p1899_jeep
'P1899 JEEP code possible causes · Faulty Park/Neutral Switch · Park/Neutral Switch harness is open or shorted · Park/Neutral Switch circuit poor electrical ...

You made the classic DIY mistake--replacing whatever part is listed in the trouble code without doing any diagnostic work. P0155 relates the o2 sensor HEATER circuit. That can be caused by an open wire or a blown fuse. Until you fix that, the oxygen sensors won't work properly and that can cause a P0432. First fix the P0155 issue

Then fix the P0455 Evaporative Emission Control System Leak Detected (gross leak) issue. THEN see if the P0432 goes away.

bank 1 is the right hand bank looking at the rngine from the front on a convention car or the bank closest to the fire wall on an east west set up
o2 sensors are always after the cat converter
HO2S or heated oxygen sensor which are different to O2 sensors are always in the exhaust manifold or pipe before the cat converter

On Grand Cherokee oxygen sensor locations for 4.0 and 4.7 engines, check this diagrams...







The Oxygen Sensors (O2S) are attached to, and protrude into the vehicle exhaust system. Depending on the emission package, the vehicle may use a total of either 2 or 4 sensors.

Federal Emissions Package (4.0L and 4.7L engines):
Two sensors are used: upstream (referred to as 1/1) and downstream (referred to as 1/2). With this emission package, the upstream sensor (1/1) is located just before the main catalytic convertor. The downstream sensor (1/2) is located just after the main catalytic convertor.


California Emissions Package (4.0L engine):
On this emissions package, 4 sensors are used: 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the rear/upper upstream sensor (2/1) is located in the exhaust downpipe just before the rear mini-catalytic convertor. The front/upper upstream sensor (1/1) is located in the exhaust downpipe just before the front mini-catalytic convertor. The rear/lower downstream sensor (2/2) is located in the exhaust downpipe just after the rear mini-catalytic convertor, and before the main catalytic convertor. The front/lower downstream sensor (1/2) is located in the exhaust downpipe just after the front mini-catalytic convertor, and before the main catalytic convertor.


California Emissions Package (4.7L engine):
On this emissions package, 4 sensors are used: 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the right upstream sensor (2/1) is located in the right exhaust downpipe just before the mini-catalytic convertor. The left upstream sensor (1/1) is located in the left exhaust downpipe just before the mini-catalytic convertor. The right downstream sensor (2/2) is located in the right exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor. The left downstream sensor (1/2) is located in the left exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor.

Hope this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using Fixya, and have a nice day.

Ho Joanne:
On Grand Cherokee oxygen sensor locations for 4.0 and 4.7 engines, check this diagrams...







The Oxygen Sensors (O2S) are attached to, and protrude into the vehicle exhaust system. Depending on the emission package, the vehicle may use a total of either 2 or 4 sensors.

Federal Emissions Package (4.0L and 4.7L engines):
Two sensors are used: upstream (referred to as 1/1) and downstream (referred to as 1/2). With this emission package, the upstream sensor (1/1) is located just before the main catalytic convertor. The downstream sensor (1/2) is located just after the main catalytic convertor.


California Emissions Package (4.0L engine):
On this emissions package, 4 sensors are used: 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the rear/upper upstream sensor (2/1) is located in the exhaust downpipe just before the rear mini-catalytic convertor. The front/upper upstream sensor (1/1) is located in the exhaust downpipe just before the front mini-catalytic convertor. The rear/lower downstream sensor (2/2) is located in the exhaust downpipe just after the rear mini-catalytic convertor, and before the main catalytic convertor. The front/lower downstream sensor (1/2) is located in the exhaust downpipe just after the front mini-catalytic convertor, and before the main catalytic convertor.


California Emissions Package (4.7L engine):
On this emissions package, 4 sensors are used: 2 upstream (referred to as 1/1 and 2/1) and 2 downstream (referred to as 1/2 and 2/2). With this emission package, the right upstream sensor (2/1) is located in the right exhaust downpipe just before the mini-catalytic convertor. The left upstream sensor (1/1) is located in the left exhaust downpipe just before the mini-catalytic convertor. The right downstream sensor (2/2) is located in the right exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor. The left downstream sensor (1/2) is located in the left exhaust downpipe just after the mini-catalytic convertor, and before the main catalytic convertor.

Hope this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using Fixya, and have a nice day.

There's noway all four o2 sensor can go out at the same time, need to check for a vacuum leak, that will set an o2 sensor code.

O2 sensors are tricky. sometimes like anything else they fail. many times though the exhaust mixture they encounter is out of their range and that shows up as a failure.since you seem to have no other problems , I would go ahead and change them, but don't be disappointed if the code shows up again (at least you know it's not the sensors.) I don't like using the process of elimination when doing repairs but sometimes you must.

There are fuses for oxygen sensor heaters. Check for 12 volts to the sensor with key on.

First of all if it is a 6 cylinder its an inline engine (4.0L). The reason I bring this up is it changes your O2 sensor configuration. Bank 1 sensor 1 ( there is only one bank because only 1 manifold) is the primary O2 sensor controlling the air/fuel ratio dependant on other sensors. Bank 1 sensor 2 is After the cataylistic converter. Depending on the code if low input or high input could be wiring and not a sensor at all. Also a low flow or high flow could indicate somebody previously "punched" the converter out or it is getting clogged due to age and mileage. Hope this helps.