How many o2 sensore are on the 99 bravado? I replaced the o2 sensor before the cat converter, now code says bank one( before cat.) needs replacing. are there 4?

Bank one is front side of cat. It should also tell u if it's cat 1 or cat 2. Depending on make an modle an yr. Catalyst 1 bank 2 is left cat back sensor. Catalyst 2 bank 2 is right cat back sensor. U do not have to replace upstream also. My o2 sensor Catalyst 2 bank 2 went bad. Had engine code for burning rich bank 2. Replaced tha down stream sensor an fixed problem runs better an better gas. This was in 97 gmc suburban. Idk what vehicle ur askin about. An I'm not to familiar with much about cars jus trucks an suvs.

code p 420 refers to cat converter system , bank 1--efficiency below threshold ===causes ---cat converter faulty---wiring --heated oxygen sensor (HO2S), 2 faulty
code p 0134 refers to HO2S 1 bank 1-no activity detected ===causes --wiring open circuit -- heating inoperative --- HO2S
also refers to oxygen sensor ( O2S) 1 bank 1--no activity detected == causes wiring ---O2S
code p 0138 refers to HO2S 2 bank 1--high voltage === causes ---wiring short to positive ---HO2S--- ECM
also refers to O2S 2 bank 1 high voltage === wiring short to positive O2S -- ECM
I do not have a listing for code p 1338 but I suspect that it will refer to the other codes in some way
first fix is to check the cat converter is operational ( not cracked and blocking the exhaust system)
next replace the HO2S sensor ( one before the cat converter ) and then the O2 sensor (the one after the cat converter)
all the codes will relate to problems in that area

o2 sensor id fai;led and needs replacing
the heater control is for the HO2S sensor which is different to the O2 sensor
the heater control sensor (HO2S) is before the cat converter and the O2 sensor is after the cat converter
because you have bank 1 then there are 2 HO2S sensors and 2 O2 sensors

O2 sensors are always after the cat converter and HO2S sensors are always before the cat converter.
p0135 refers to heated oxygen sensor(HO2S) 1 bank 1-heater control--circuit malfunction
If it is a straight 6 cylinder engine with 2 cat converters it will be the sensor before the cat converter that connects to the manifold from pistons 1.2.3
If it is a V6 it will be the sensor that is in front of the cat converter that connects to the rear bank pistons 1.2.3. Use the special socket when removing/replacing the sensors to prevent wiring damage

P0421 code is that the cat. converter is below efficiency. 99 per cent o the time the cat. needs to be changed. but if you have a scan tool watch both bank 1 O2 sensor 1 and bank 1 sensor 2.
cold they should be almost the smae but when its at operating temp, and running down the road at crusie speed the frt o2 should switch rapidly between .150 mv. and .850 mv. and the rear o2 should read about .600 mv. if they read the same the cat is ng and will have to be replaced.

Hi.

P0032 means HO2S Heater Control Circuit High (Bank 1 Sensor 1).

It means high impedance from O2 sensor, check wiring to sensor and replace the sensor.
Check O2 sensor located in bank 1 (cylinder 1 side- see here), and after the catalitic converter (there is also an O2 sensor before cat converter).

It is not true that you have to replace the O2 sensors when you replace the catalytic converter. It is suggested, but not required. Most exhaust shops can test the catalytic converter for flow. before you spend the money to replace a part that does not need it.

P0155 is o2 sensor heater circuit malfunction bank 2 sensor 1 it is the o2 sensor circuit in front of the cat converter the o2 sensors are located mounted to the exhaust pipe in front and behind the catylic converter the problem is in the circuit [wiring or sensor itself] check wiring and repair if necessary if the short or open circuit is the sensor need to replace sensor +++ P0161 is 02 sensor heater circuit malfunction BANK 2 SENSOR 2 ++++++ this is the sensor behind the cat converter

from what i am finding the code means o2 sensors. they recommend replacing them and if this does not work than replacing the cat converter

The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

causes

A code P0420 may mean that one or more of the following has happened:

• Leaded fuel was used where unleaded was called for
• An oxygen sensor is not reading (functioning) properly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
• Retarded spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings

possible soloutions

Some suggested steps for troubleshooting a P0420 code include:

• Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
• Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
• Inspect the downstream heated oxygen sensor (HO2), replace if necessary
• Replace the catalytic converter

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.


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That is the O2 sensor right behind the cat. converter. When the cat is clogged it can shoot contaminates in the O2 sensor so sometime just cleaning the sensor will make it work again, if not it will need to be replaced. Mark - ABKS