Tip & How-To about Ford F-150

Which Oxygen Sensor Is It?

There are many inquiries online about which oxygen sensor to change. Oxygen sensor failure codes are very common on a lot of vehicles. With all of today's vehicles having at least two oxygen sensors and many having three or four of them, it can be a little confusing as to which one is causing the problem.

Before we get into which sensor is which, we need to have a little discussion about oxygen sensor fault codes. There are several different types of oxygen sensor fault codes. Here are just some of the most common ones:

P0135 "Oxygen Sensor Heater Circuit Bank1 Sensor 1"
P0141 "Oxygen Sensor Heater Circuit Bank 1 Sensor 2"
P0147 "Oxygen Sensor Circuit Bank 1 Sensor 3"
P0152 "Oxygen Sensor Voltage High Bank 2 Sensor 1"
P0159 "Oxygen Sensor Slow Response Bank 2 Sensor 2"
P0171 "Oxygen Sensor Lean Sensor 1 Bank 1"
P0172 "Oxygen Sensor Lean Sensor 1 Bank 2"
P0174 "Oxygen Sensor Rich Sensor 1 Bank 1"
P0175 "Oxygen Sensor Rich Sensor 1 Bank 2"

There are many more possible oxygen sensor codes, but I only listed these to make my point. Many times the oxygen sensor code is NOT caused by the oxygen sensor itself. "Lean" or "Rich" oxygen sensor codes (i.e. P0171, P0174) are usually caused by something other than the oxygen sensor. Something is wrong, causing the engine to run lean (not enough fuel or too much air) or causing the engine to run rich (too much fuel or not enough air). In these cases, replacing the oxygen sensor will not fix a thing. (That is, unless you are trying to fix your bank account from having too high of a balance!) The new oxygen sensor will just set the same code as the original one. This is because the oxygen sensor is not CAUSING the problem, it is only REPORTING the problem.

High voltage codes (like P0152 above) can be caused by the oxygen sensor wires being shorted to another wire inside the wiring harness. Sometimes these codes are caused by bad grounds where some other component is trying to ground through the oxygen sensor circuit. Again, replacing the oxygen sensor will not fix this! In short, the problem needs to be diagnosed before running out and buying an oxygen sensor.

Just because a fault code has "Oxygen Sensor" or "O2 Sensor" or "O2S" in its description does not necessarily mean that an oxygen sensor needs to be replaced. Many do-it-yourselfers believe that all there is to fixing the car is to hook it to the "magic box", collect the fault codes and replace the parts the computer tells you to replace. There is nothing further from the truth.

Fault codes only point you toward which SYSTEM is failing. The system must be diagnosed to find the CAUSE of the failure. If this is not done properly, it will only result in wasting a bunch of your money. This is what you were trying to avoid by doing it yourself!

So, after reading all of the above, if you think you still want to replace an oxygen sensor, but don't know which one; here is how to figure it out:

Oxygen sensors are always numbered like this:

Bank 1 Sensor 1
Bank 2 Sensor 1
Bank 1 Sensor 2
Bank 2 Sensor 2

Some manufacturers use a kind of shorthand that reads different, but means the same thing:

Sensor 1/1 or O2s 1/1
Sensor 2/1 or O2s 2/1
Sensor 1/2 or O2s 1/2
Sensor 2/2 or O2s 2/2

Bank 1 is always the side of the engine where cylinder #1 is located and, of course, Bank 2 is the opposite side.
On a 4 cylinder engine, there is only one bank and it is always referred to as Bank 1. The exception to the 4 cylinder rule is on certain 4 cylinder engines (specifically, some Toyotas) there are two catalytic converters used. In this case, Bank 1 sensors will still be in the pipe for the catalyst that is connected to cylinder #1 and Bank 2 sensors will be in the other one.

Sensor 1 is always the "upstream" sensor (the one located BEFORE the catalytic converter).
Sensor 2 is always the "downstream" sensor (the one that is located AFTER the catalytic converter).
Sensor 3 refers to the ONLY "downstream" sensor where there are two sensors before the catalyst and only one after the catalyst. On very few vehicles the reference to this reads "Bank 1 Sensor 3".

If you do not know where cylinder #1 is, then you need to get a diagram of the firing order for your engine. Just post a question on FixYa.com and make sure you give the YEAR, MAKE, MODEL, and ENGINE SIZE of your vehicle and one or more of our experts will be happy to tell you how to find cylinder #1.

- DTTECH
ASE Certified Master Automobile Technician


Also check out this article by dttech: What Else Could Be Wrong?

Posted by on

Cars & Trucks Logo

Related Topics:

Related Questions:

1 Answer

I just replaced both o2 sensors pre-cat converter and can't clear the service engine light on an 01 yukon. I tried pulling the fuse, disconnect battery with no luck. In research I noticed that the dealer gave a different sensor than was in there from Delphi. Does that matter. Both are oem.


I think you need Bosch for that vehicle. here is a rundown how it helps


Every automobile manufactured after the 1980s is equipped with an oxygen sensor. This component measures the ratio of air and gasoline in the engine and feeds the data to the vehicle's computer. With an oxygen sensor, your engine runs more efficiently and produces as few emissions as possible. If your car's running with a busted oxygen sensor, you better get a new one before your engine's efficiency takes a nosedive and your gas bills skyrocket. We know that looking for the right replacement oxygen sensor can be very tricky, that's why we've come up with a guide for you to keep in mind when shopping for a new oxygen sensor.
Which oxygen sensor should you buy?
There are a lot of questions about which oxygen sensor to replace. In fact, failures are common among cars especially when the wrong sensor is installed. With today's automobiles equipped with at least two, or even three or four oxygen sensors, it can be very confusing as to which one is not working correctly. There are probably a lot of sensor codes to choose from and here's a tip to help you sense the right oxygen sensor.
Oxygen sensors are always numbered this way:
Bank 1 Sensor 1
Bank 2 Sensor 1
Bank 1 Sensor 2
Bank 2 Sensor 2
Other manufacturers code their oxygen sensors this way, which is why it can sometimes be very confusing. However, they all mean the same:
Sensor 1/1 or O2s 1/1
Sensor 2/1 or O2s 2/1
Sensor 1/2 or O2s 1/2
Sensor 2/2 or O2s 2/2
Now here's a detailed list to know which is which:
  • Bank 1 is located at the side of the engine where cylinder #1 is found as well.
  • Bank 2 is on the opposite side of Bank 1.
  • On a 4-cylinder engine, there is only one bank that's called Bank 1.
  • Sensor 1 is the upstream sensor located before the catalytic converter.
  • Sensor 2 is the downstream sensor located after the catalytic converter.
  • Sensor 3 is the only downstream sensor in situations where there are two sensors before the catalytic converter and only one after it. On other cars, this is read as Bank 1 Sensor 3.
With these detailed tips on how to sense the right oxygen sensor, you'd be sure to buy the right replacement part at your store. Be sure to purchase one from a trusted brand to avoid any complications you might experience with ones that are bought from local junkyards BEST OF LUCK

Aug 26, 2013 | Dodge Grand Caravan Cars & Trucks

1 Answer

Cant Find a list of codes 1989 Buick Century. Car stalls and has a rough idle. coads are 31 43 and 44


Here is a code list for you. Remember this doesn't always mena a sensor issue, the problem can be in the wiring as well, or in the case of a lean code you may have an actual lean condition due to a vacuum leak at the intake or vacuum hoses or connections. I have highlighted your fault codes and added extra notes.
GM common codes for OBD1 (for vehicles made before 1995)
12 System normal
13 oxygen sensor circuit open
14 coolant sensor high resistance or shorted
15 coolant sensor circuit low or open
16 direct ignition system (DIS) fault in circuit
17 cam position sensor fault
18 crank or cam sensor error
19 crank sensor circuit fault
21 tps sensor out of range
22 tps sensor signal voltage low
23 intake air temp sensor out of range, low
24 vehicle speed (vss) sensor circuit fault
25 air temp sensor sensor out of range, high
26 quad-driver module (computer) circuit #1 fault
27 quad-driver module (computer) 2nd gear circuit
28 quad-driver module (computer) circuit #2 fault
29 quad driver module (computer) 4th gear circuit
31 camshaft position sensor fault
32 egr circuit fault
33 map sensor signal out of range, high
34 map sensor signal out of range, low
35 idle air control sensor circuit fault
36 ignition system circuit error
38 brake input circuit fault
39 clutch input circuit fault
41 cam sensor circuit fault, igntion control circuit fault
42 electronic spark timing (EST) circuit grounded
43 knock sensor malfunction or electronic spark control (ESC) circuit fault (ignore this for now)
44 oxygen sensor lean exhaust (make sure you no engine vacuum leaks)

45 oxygen sensor rich exhaust
46 pass-key II circuit or ps.pressure switch circuit fault
47 pcm-bcm data circuit
48 misfire diagnosis
51 calibration error, mem-cal, ecm or eeprom failure
52 engine oil temperature circuit, low temperature indicated
53 battery voltage error or egr or pass-key II circuit
54 egr system failure or fuel pump circuit low voltage
55 a/d converter error or pcm not grounded or lean fuel or frounded reference voltage
56 quad-driver module #2 circuit
57 boost control problem
58 vehicle anti-theft system fuel enable circuit
61 a/c system performance or degraded oxygen sensor signal
62 engine oil temperature high temperature indicated
63 oxygen sensor right side circuit open or map sensor out of range
64 oxygen sensor right side lean exhaust indicated
65 oxygen sensor right side rich exhaust indicated
66 a/c pressure sensor circuit low pressure
67 a/c pressure sensor circuit or a/c clutch circuit failure
68 a/c compressor relay circuit failure
69 a/c clutch circuit head pressure high
70 a/c refrigerant pressure circuit high
71 a/c evaporator temperature sensor circuit low
72 gear selector switch circuit
73 a/c evaporator temperature circuit high
75 digital egr #1 solenoid error
76 digital egr #2 solenoid error
77 digital egr #3 solenoid error
79 vehicle speed sensor (vss) circuit signal high
80 vehicle speed sensor (vss) circuit signal low
81 brake input circuit fault
82 ignition control (IC) 3X signal error
85 prom error
86 analog/digital ecm error
87 eeprom error
99 power management

Jul 21, 2011 | 1989 Buick Century

2 Answers

what is the code p00300


this is an obd2 trouble code table, it can help you understand the meaning of code.
for po300:
Possible causes of OBD code P0030:
Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit open shorted to ground - Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit poor electrical connection - Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit - Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit fuse - Faulty Engine Control Module (ECM) The Error code is generally activated on detection of the following conditions: The P0030 is set when the ECM detects an open or shorted to ground condition on the heated oxygen sensor heater circuit
Possible Solutions:
The code means that there is a problem with the heater element circuit of the heated oxygen sensor. Water getting inside the heated oxygen sensor connector can caused the heated oxygen sensor fuse to blow, which is a very common problem for this type codes. Before replacing the sensor, check for the condition of the heated oxygen sensor fuse and connectors. HO2S Heater Control Circuit Bank 1 Sensor 1 is the generic definition for the P0030; however your vehicle's manufacturer may have a different definition and information for the P0030 code.
hope help.

Jun 22, 2011 | Nissan Altima Cars & Trucks

1 Answer

when i pull the code up on my 1992 park avenue it blinks once then blinks twice. what does this code mean?


This is code 12 and it means "System Normal"
Here is the complete list of fault codes for your Buick
GM common codes for OBD1 (for vehicles made before 1995)
12 System normal
13 oxygen sensor circuit open
14 coolant sensor high resistance or shorted
15 coolant sensor circuit low or open
16 direct ignition system (DIS) fault in circuit
17 cam position sensor fault
18 crank or cam sensor error
19 crank sensor circuit fault
21 tps sensor out of range
22 tps sensor signal voltage low
23 intake air temp sensor out of range, low
24 vehicle speed (vss) sensor circuit fault
25 air temp sensor sensor out of range, high
26 quad-driver module (computer) circuit #1 fault
27 quad-driver module (computer) 2nd gear circuit
28 quad-driver module (computer) circuit #2 fault
29 quad driver module (computer) 4th gear circuit
31 cam position sensor fault
32 egr circuit fault
33 map sensor signal out of range, high
34 map sensor signal out of range, low
35 idle air control sensor circuit fault
36 ignition system circuit error
38 brake input circuit fault
39 clutch input circuit fault
41 cam sensor circuit fault, igntion control circuit fault
42 electronic spark timing (EST) circuit grounded
43 knock sensor
or electronic spark control circuit fault
44 oxygen sensor lean exhaust
45 oxygen sensor rich exhaust
46 pass-key II circuit or ps.pressure switch circuit fault
47 pcm-bcm data circuit
48 misfire diagnosis
51 calibration error, mem-cal, ecm or eeprom failure
52 engine oil temperature circuit, low temperature indicated
53 battery voltage error or egr or pass-key II circuit
54 egr system failure or fuel pump circuit low voltage
55 a/d converter error or pcm not grounded or lean fuel or frounded reference voltage
56 quad-driver module #2 circuit
57 boost control problem
58 vehicle anti-theft system fuel enable circuit
61 a/c system performance or degraded oxygen sensor signal
62 engine oil temperature high temperature indicated
63 oxygen sensor right side circuit open or map sensor out of range
64 oxygen sensor right side lean exhaust indicated
65 oxygen sensor right side rich exhaust indicated
66 a/c pressure sensor circuit low pressure
67 a/c pressure sensor circuit or a/c clutch circuit failure
68 a/c compressor relay circuit failure
69 a/c clutch circuit head pressure high
70 a/c refrigerant pressure circuit high
71 a/c evaporator temperature sensor circuit low
72 gear selector switch circuit
73 a/c evaporator temperature circuit high
75 digital egr #1 solenoid error
76 digital egr #2 solenoid error
77 digital egr #3 solenoid error
79 vehicle speed sensor (vss) circuit signal high
80 vehicle speed sensor (vss) circuit signal low
81 brake input circuit fault
82 ignition control (IC) 3X signal error
85 prom error
86 analog/digital ecm error
87 eeprom error
99 power management

May 05, 2011 | Buick Park Avenue Cars & Trucks

2 Answers

looking for code 32 for a 5.2 litre jeep grand cherokee


EGR System Failure...Open or short circut on the EGR solenoid circut.

Feb 14, 2011 | Jeep Grand Cherokee Cars & Trucks

Not finding what you are looking for?

3,682 people viewed this tip

Ask a Question

Usually answered in minutes!

Top Ford Experts

yadayada
yadayada

Level 3 Expert

75051 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22095 Answers

fordexpert

Level 3 Expert

5470 Answers

Are you a Ford Expert? Answer questions, earn points and help others

Answer questions

Loading...