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Vacuum leak causing the o2 sensor to malfuction

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Yes, a leak changes fuel/air mix, and shows as a sensor out of range. A squirt bottle with water can help locate leak by misting water around one area at a time, and listen for change in sound of engine.

Posted on Sep 02, 2012


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2003 ford explorer 4.6 has engine code p2195

I don't know what you want or how you want to move forward with this issue. Give me an idea how you want to proceed and what additional diagnostic information you want. I am forwarding code information and possible causes. Let me know if you need anything else. Good Luck. Potential causes of a P2195 code include: Oxygen (O2) or A/F ratio sensor or sensor heater malfunction Open or short in O2 sensor circuit (wiring, harness) Fuel pressure or fuel injector problem Faulty PCM Intake air or engine vacuum leaks Faulty fuel injector(s) Fuel pressure too high or too low PCV system leak/fault A/F sensor relay faulty MAF sensor malfunction ECT sensor malfunction Fuel pressure too low Fuel leak Air suction in air intake system

P2195 is an OBD-II generic code for the engine control module (ECM) detecting the O2 sensor signal stuck lean for bank 1 sensor 1. The engine has tried to lean out a rich condition and failed.
Potential causes of a P2195 code include:
-Oxygen (O2) or A/F ratio sensor or sensor heater malfunction
-Open or short in O2 sensor circuit (wiring, harness)
-Fuel pressure or fuel injector problem
-Faulty PCM Intake air or engine vacuum leaks
-Faulty fuel injector(s)
-Fuel pressure too high or too low
-PCV system leak/fault
-A/F sensor relay faulty
-MAF sensor malfunction
-ECT sensor malfunction
-Fuel pressure too low
-Fuel leak Air suction in air intake system

Sep 18, 2018 | Ford Cars & Trucks

1 Answer

Codes po171 , po136

PO171 is the 1st o2 sensor on bank 1. With that said a vacuum leak will also throw this same code so before I go changing an o2 sensor I would completely go over the engine and look for a vacuum line or intake leak. PO136 is the o2 sensor bank 1 the second sensor in the exhaust. Again here are some of the things that can cause this code. ( I always look for a vacuum leak somewhere first)

Jul 06, 2014 | 1988 Ford Ranger

1 Answer

Fuel trim malfuction

You got that discription from where or whom?

Fuel trim comes in two forms

Short Term --- for fuel adjustments on the current start up
& driving trip.

Long Term---for an avg of the last several times out,
& is a factor used to adjust fuel when the engine is cold
& first started

After the thermostat is open & the temp sensor is satisfied,
the computer goes to closed loop & uses the O2 Sensors to
adjust fuel (short term)

You need the codes produced to diagnose the issue
There could be several things that effect fuel trim.

A failing fuel pump,thus low pressure or volume
Worn out O2 Sensors
Worn out and damaged exhaust converter
Any Vacuum Leaks anywhere on any system
Leaking (vacuum) Intake Manifold or Exhaust Leaks
effecting the O2's
Coolant Temp Sensor
Many more I guess

Without the codes & more discription we can only
say it has to be checked out & scan tool data looked at

A simple loose air filter cover from sloppy work, could
upset things,but would effect both sides of engine,as air
in is common to intake,not bank specific

Jul 09, 2012 | 2000 Mercedes-Benz S-Class

1 Answer

I have the P0133 code bank 1 sensor 1, i know it could be the O2 sensor but when i disconnect the service hose leading to the evap canister it runs better but only for a little bit. im not sure why that...


Apr 18, 2011 | Dodge Stratus Cars & Trucks

1 Answer

Symptons o2 sensors

If your O2 sensors are malfunctioning, the main symptom would be that the Check Engine light will come on. On some vehicles, an O2 sensor circuit shorted to ground can cause a no-start problem.
If the "Check Engine" or "Service Engine Soon" light is on and there is a code for the O2 sensors, I would like to also advise you that many O2 sensor codes are not caused by the O2 sensors themselves. In many cases, the O2 sensors are only REPORTING the problem. for example, a code P0171 "Oxygen Sensor Lean" code is rarely ever caused by the O2 sensor. It is usually caused by a vacuum leak or a failed Mass Airflow sensor (MAF) or Manifold Absolute Pressure sensor (MAP) or a bad fuel injector. In these cases, repairing the real reason that the engine is running lean will fix the O2 Sensor code without replacing the O2 sensor.

Mar 12, 2011 | 2000 Chevrolet 3500

1 Answer

I have 04 f150 fx4 with the 5.4 my check engine light is on code read o2 sensor repaced same one twice andstill say that the o2 sensor is bad why

O2 Sensor codes rarely mean that the O2 Sensors are defective. Most of the time, the O2 sensors are reporting a problem that is occuring somewhere else in the system. If your are getting a code that says "O2 sensor lean" that means that someting on that side of the engine is causing that side to be running lean. This is usually caused by a vacuum leak, but may also be caused by bad injectors or low fuel pressure. If BOTH sides are reporting lean O2 Sensor codes at the same time, it is something wrong that affects both sides of the engine including vacuum leaks in the main hoses tied into the intake manifold including the PCV hose and the Brake Booster Vacuum hose or the brake booster itself, or the Mass Airflow Sensor. Defective Engine Coolant Temperature sensors can also cause these codes. If the code you are getting is a "O2 Sensor Rich" code, it is caused by something that is making the engine run rich. This could be a sticking injector, a failed Fuel Pressure Regulator, or an O2 Sensor circuit that is shorted to voltage, or a malfunctioning Mass Airflow Sensor.
If you want to save a lot of money and frustration, learn this: Fault codes NEVER tell you what parts to replace. Fault codes only tell you which of the many systems monitored by the computer are operating outside their expected ranges or "Window of Operation". It is up to the person diagnosing the vehicle to test the system that is reporting the malfunction and determine the cause of the failure and repair as necessary.

Jan 21, 2011 | 2004 Ford F150

2 Answers

What do you think the chances are that a maf sensor is causing codes p0171 and p0174,causing the check engine light to come on?

Clean the MAF Sensor---CRC MAF Cleaner
The maf sensor is fairly reliable and fairly expensive.
They just repair them,so I would say no

Vacuum leaks are the most likely,causing both banks, to drive the O2 Lean

Egr Valve worth checking out

Loose O2 Sensors

Exhaust letting air in

Ducting to throttle or air filter cover loose


Nov 05, 2010 | Mercury Grand Marquis Cars & Trucks

1 Answer

02 sensor p0136 and cylinder misfire p0300

Most likely you do not have bad O2 sensor or coil sience you have P0300 code.
Check for vacuum leaks first , this is very common problem(vacuum leak) , lean mixture will cause misfire. I'm tallking about V6 engine , 4cyl have same problems but for misfire it may have bad coil (they under recall now).
Also check condition of air mass sensor , if it's dirty ,
buy air flow sensor cleaner and clean it according to user manual on the can.(air mass sensor can cause
O2 sensor code)
Check vacuum hose to fuel pressure regulator.
There are many more things to check , but that for mechanic shops after you try this.

Jun 10, 2010 | 2001 Audi A4

3 Answers

All 4 o2 sensors read bad

daves944 knows what he is talking about, u need to find the root cause of this problem, which is a problem any of th following can cause this, MAF, Intake leaks, engine conditions like low compression and many other things, the O2 codes are a Symptom not the problem, you may also have a wiring harness problem, check the harness connectors to the O2 sensors, look for exhaust heat related wiring damage, look for corrosion in connectors.

May 01, 2009 | Ford F-150 Cars & Trucks

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