Question about 2000 Ford Expedition

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Service engine soon light is on. Have already replaced downstream oxygen sensor, as code # 174, (lean burn), indication on egine code. Should I replace all oxygen sensors?

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  • Anonymous Mar 21, 2014

    check egine light came on ran code is it easy to change

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  • Ford Master
  • 7,716 Answers

Hi, no, don't do that. The code 174 indicates a vacuum leak--not a bad sensor. The leak can be anywhere downstream of the mass airflow sensor on the inlet pipe. Sometimes the rubber pipe itself tears/cracks, or maybe there is a loose vacuum hose or a torn brake booster diaphram. Check all the hoses attached to the engine intake manifold for a leak at either end or in between.
If all hoses are good, next check the intake manifold askets for leaks. Get yourself a can of carb cleaner and start the engine. Spray the gaskets all around. If the engine speed changes, you have a gasket leak--replace the gaskets. Since you have a code 174 and NOT a code 171, this is the most likely cause of the problem, because only the rigt bank is running lean. Be sure to check the gaskets on that passenger side carefully.
Last of all, if all that was good, check to see if your EGR valve is stuck open. I have pasted instructions for removing the valve below (from autozone.com). Please let me know if you have questions and thanks for using FixYa.


EGR valve R&R.

  1. Disconnect the negative battery cable.
  2. Remove the vacuum hose from the EGR valve.
  3. On the 4.6L engine, remove the nut and the brake booster bracket.
  4. Service engine soon light is - jturcotte_117.jpg
  5. On the 5.4L engine, remove the DPFE sensor retaining nuts and place the sensor to the side to allow access to the EGR tube.
  6. Disconnect the EGR valve-to-exhaust manifold tube from the EGR valve.
  7. jturcotte_118.jpg
  8. Remove the EGR valve mounting bolts, then separate the valve from the intake manifold.
    1. jturcotte_119.jpg
  9. Remove and discard the old EGR valve gasket, and clean the gasket mating surfaces on the valve and the intake manifold.

To install:
  1. Install the EGR valve, along with a new gasket, on the intake manifold, then install and tighten the mounting bolts.
  2. Connect the EGR valve-to-exhaust manifold tube to the valve, then tighten the tube nut to 25-35 ft. lbs. (34-47 Nm).
  3. Connect the vacuum hose to the EGR valve.
  4. On the 5.4L engine, install the DPFE sensor.
  5. On the 4.6L engine install the brake booster bracket and the retaining nut.
  6. Connect the negative battery cable.

      Posted on Jan 03, 2011

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      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

      http://engine-codes.com/p1131_ford.html

      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: http://engine-codes.com/p1131_ford.html#ixzz3izk89wMu

      Aug 16, 2015 | Ford Cars & Trucks

      1 Answer

      Replaced bank 1 and bank 2 downstream oxygen sensors on 2004 5 speed automatic diagnostic code still says not working


      Try resetting the codes by removing both terminals on the battery for 10 minutes. After the codes should be rest if they do not come back on the sensors are fine.

      Jun 28, 2013 | Cars & Trucks

      3 Answers

      Just changed the PLASTIC INTAKE on 2002 Ford Explorer its now has service engine soon. Pulling codes P0171, P0174, P0203. Does anyone know what this could be?


      Check your work for vacuum leaks,can't have any

      Replace the front oxygen sensors, if they have 100,000
      miles on them That is the 171&174 along with vacuum leaks
      & worn out slow sensors

      PO203 ---is a #3 injector issue

      Listen to hear if it ticks-- like the others & compare
      OHM readings to the others

      Nov 30, 2012 | 2002 Ford Explorer

      3 Answers

      Po174 and po154 what is possible solutions


      P0154 - 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
      The oxygen sensors are critical to the engine running properly. It basically informs the PCM (Powertrain Control Module) of oxygen content of the exhaust. The PCM then uses this information to regulate fuel into the engine and maintain proper air:fuel ratio. It is a four wire sensor, with the PCM providing a reference/signal voltage of about half a volt (0.5v) to the sensor. It usually provides a ground also. The other two wires are dedicated to the oxygen sensor heater element. This heater allows the sensor to warm up faster, which allows the engine to enter closed loop faster, reducing startup emissions. The heater element is supplied a 12v feed from the power distribution center (usually) and a ground.

      The oxygen content of the exhaust affects the O2 sensor resistance. This resistance produces a counter voltage on the reference/signal wire that the PCM will use to analyze oxygen in the exhaust. Lean exhaust produces low voltage, while rich exhaust produces high voltage. The oxygen sensor is capable of varying between 0.9v (rich) and 0.1v (lean). Once the engine reaches closed loop, the O2 sensor should begin switching rapidly between rich and lean voltages 2-3 times per second. If for some reason the O2 sensor doesn't switch properly or "sticks", P0154 may set. This code indicates the O2 sensor isn't operating.


      P0174 - System Too Lean (Bank 2)
      Basically this means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 2 is generally the side of the engine that doesn't have cylinder #1.

      Note: This DTC is very similar to P0171, 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.


      If need additional details, just contact us. Hope this helps.

      Oct 04, 2011 | 1999 Oldsmobile Alero

      1 Answer

      P1131,p1151,p0174


      Hello,
      P1131 = Lack of HO2S11 switch - sensor indicates lean, ( upstream heated oxygen sensor )
      This oxygen sensor is located before the catalytic converter, ( refered to as UPSTREAM )

      P1151 = Lack of HO2S21 switch - sensor indicates lean, ( could be up, or downstream heated oxygen sensor ) " Downstream ", meaning after the catalytic converter.

      PO174 = System too lean, ( bank 2 ) The fuel/air mix ratio is bad.

      These DCT codes are generally caused by a problem with the emissions system. The following items are a few of the most common items to trigger those codes.

      1. Dirty air filter. ( very common )
      2. Faulty idle air control valve. ( common )
      3. MAF, ( mass air flow ), sensor. ( very common )

      All 3 of the above can prevent the onboard computer from determining the proper fuel/air mix ratio.
      The oxygen sensors measure to insure the fuel/air mix produces maximum power with minimal emissions.

      I hope this helps you.
      Feel free to contact me in the comment section if you have a question.

      Feb 15, 2011 | 2002 Ford F150 Regular Cab

      1 Answer

      What causes the P1278 code in a 2005 Nissan Altima? I replaced the catalytic converter, up and downstream O2 sensors, cleared the code, and the 'Service Engine Soon' light still comes on.


      CODE P1278- HEATED OXYGEN SENSOR 1 SLOW RESPONSE.POSSIBLE CAUSE EXHAUST LEAK AT EXHAUST MANIFOLD OR PIPES.FAULTY PRESSURE REGULATOR LEAKING OR FUEL INJECTORS LEAKING.AND FAULTY TPS SENSOR

      Jan 23, 2011 | Nissan Altima Cars & Trucks

      2 Answers

      1999 Chevy silverado 5.3 engine setting codes p171 p174 already replaced mas air flow and checked for leaks


      oxygen sensor failure
      P0171 System too Lean (Bank 1) - Read Our Article On Oxygen Sensor Codes For Help With This Generic Check Engine Light Code
      P0174 System too Lean (Bank 2) - Read Our Article On Oxygen Sensor Codes For Help With This Generic Check Engine Light Code
      hope this is a bit of a push in the right direction ...

      Feb 02, 2010 | 1999 Chevrolet Silverado 1500

      3 Answers

      Engine light on mercury mountaineer code PO 174 PO 171 how do i fix it......


      mass air flow sensor & the PVC assembly needs to be replaced

      Jan 16, 2010 | 1998 Mercury Mountaineer

      1 Answer

      I have replaced all 4 ox senors before I replaced intake man. gaskets. It is a 97 chevy W/Truck with a V6 auto, auto trans. 2WD. now service engine soon light came on after about 200 miles, it will go off...


      First did you clear all the fault codes after your repairs? The reason I ask is po131 is bank one oxygen sensor, po174 is engine lean from faulty oxygen sensor, and po171 is engine lean condition, possibly from vacuum leak (intake manifold gasket?), pcv valve,etc. To check for vacuum leak at intake, start engine and gently spray starting fluid around intake gasket. If rpm raise slightly while doing this then there is a vacuum leak(stay away from air filter intake and housing though), and the gasket will need to be replaced again.

      Jan 09, 2010 | 1997 Chevrolet C1500

      1 Answer

      Check engine light is on,codes 171,174,system lean,codes came back as 2 oxygen sensor's before cat/conv,do they need to be replaced or could it be something else causing it, any help would be great!!!


      O2 SENSORS ARE BAD MOST LIKELY I WOULD CHANGE THEM DISCONNECT THE BATTERY FOR 5 MIN. ( IF YOU DONT HAVE A SCANNER) THIS WILL RESET YOUR COMPUTER AND SHOULD MAKE THE SERVICE ENGINE LIGHT GO OUT.

      May 19, 2009 | 1999 Ford Ranger SuperCab

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