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What causes the HO2 bank 2 Sen 1 Switching Lean Mean

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Poss bad sensor
change it

Posted on May 28, 2010


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Usually the O2 sensor is contaminated and has a weak switching rate or is completely dead. If stuck low/lean it will cause a rich demand, if stuck high/rich it will cause a lean demand.

Dec 09, 2015 | Isuzu Axiom Cars & Trucks

2 Answers

What does code p1131 mean on a 2001 ford taurus

P1131 Ford
P1131 Ford - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1

Repair Importance Level: 3/3

Repair Difficulty Level: 2/3

Forum Code

Possible causes

- Faulty Oxygen Sensor

- Vacuum leak affecting bank 1 only

- Fuel injector problem bank 1

- Check for cylinder misfire on bank 1

- Engine mechanical condition

Tech notes

Though the Oxygen (O2) sensor, the Engine Control Module (ECM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.

When is the code detected?

The Engine Control Module (ECM) detected bank 1 oxygen (O2) at its lean limit

Possible symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

P1131 Ford Description

A Heated Exhaust Oxygen (HO2S) sensor indicating rich at the end of a test is trying to correct for an over-lean condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time.

Read more:

Aug 16, 2015 | Ford Cars & Trucks

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I have a 2001 ford expedition that bogs out when i put it in drive but runs fine in second gear.

DTC P0171 - System Too Lean (Bank 1) and P0174 - System Too Lean (Bank 2)
Basically this means that an oxygen sensor in bank 1 or bank 2 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1. Bank 2 is generally the side of the engine that doesn't have cylinder #1.
Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.

You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

A code P0171 may mean that one or more of the following has happened:
The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.There could be a vacuum leak downstream of the MAF sensor.

Possible solutions include:In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstallingInspect all vacuum and PCV hoses, replace if necessaryCheck for a dirty fuel filter and proper fuel pressure

DTC P0155 - 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)This code refers to the front oxygen sensor on Bank 2. The heated circuit in the oxygen sensor decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0155. See also: P0135 (Bank 1).

You will likely notice poor fuel economy the illumination of the MIL.

A code P0155 may mean that one or more of the following has happened:O2 Heater element resistance is high
Internal short or open in the heater elementO2 heater circuit wiring high resistanceopen or short to ground in the wiring harness

Possible SolutionsRepair short or open or high resistance in wiring harness or harness connectorsReplace oxygen sensor (cannot repair open or short that occurs internally to sensor)

DTC P0161 - Oxygen O2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)It basically means the PCM detected either an excessive current draw, or an open or short in the circuit powering the oxygen sensor's heater circuit. This is in reference to the Heated Oxygen Sensor (2) located rear of catalytic converter (Bank 2).

There will likely be no obvious symptoms other than MIL illumination.

A code P0161 may mean that one or more of the following has happened:HO2S heater power circuit openHO2S heater ground circuit openHO2S signal tracking (due to oil or moisture in the connector)HO2S is damaged or has failed PCM has failed

Possible Solutions:Replace HO2 SensorRepair open or short in power circuitRepair open or short in ground circuitRepair damaged connector due to tracking

Hope helps.

Mar 27, 2012 | 2001 Ford Expedition

1 Answer

My car had a check engine soon light come on. We put the code thing in and I got a code # P044 on my 2003 Alero. What does this mean?

P044 HO2 Bank 1 sen 3 heater circuit high

Possible causes
open or shorted to ground
2) poor electrical connection
3) fuse
4) bad sensor
Engine Control Module maybe bad

Hope this helps Tim

Apr 04, 2011 | 2001 Oldsmobile Alero

1 Answer

What does code P1151 mean when it is thrown on a 97 mustang GT with a 4.6 motor

Ford P1151 = Lack of heated oxygen sensor bank 2, sensor 1 switches, sensor indicates lean.

The oxygen sensor that is upstream of the catalytic converter on the exhaust side that covers the bank of cylinders that includes cylinder no. 2 (the even bank) is not switching rapidly enough from lean to rich. It is "stuck" on lean mode. It could be tested for proper operation and if it fails the tests, it should be replaced.

Mar 04, 2011 | Ford Mustang Cars & Trucks

1 Answer

What do the codes 1128, 1129, 1133, and 1134 mean on my Porsche Boxter 2001?

code P1128 02 sensor bank 1 lean
code P1129 02 sensor bank 1 lean to limit
code P1133 02 sensor bank 2 lean
code P1134 02 sensor bank 2 lean to limit

fuel system is lean.

Jan 29, 2011 | 2001 Porsche Boxster

3 Answers

2003 Ford Ranger 4x4 extended cab- diagnostics checked and got these codes- P0171, P0174, P0300, P0316. Can you tell me what they mean?

P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
Possible causes:
dirty/malfunctioning injectors
weak coil pack
fowling spark plugs/wires
Low fuel pressure

May 11, 2010 | 2003 Ford Ranger Regular Cab

3 Answers

2001 Toyota corolla hesitates on acceleration

Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust).

Mar 27, 2009 | 2001 Toyota Corolla

1 Answer

Diagnostic codes 97 tahoe 4d 4wd 5.7

p1460 cooling fan circuit,p1153 ho2s insufficient switching bank 2 sensor 1,p1133 insuf. swit. sen. 1 or bank 1 sen. 1,p420 catalyst system efficiency below threshold bank 1,p152 o2sen. circuit high volt. bank 2 sen.1

Feb 24, 2009 | 1997 Chevrolet Tahoe

1 Answer


It is telling you the fuel system is not seeing any closed loop switching, the signal from an O2 always varies between rich and lean, back and forth, you can have 3 things going on, one the O2 is lazy or has failed, but most times that would trip a lean code, the more likely cause is a problem in the fuel control, either to rich or to lean. without the actual voltage readings from the O2 it is hard to tell you what to replace, do you have a system monitor tool?

Aug 07, 2008 | 1993 Saturn SL2

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