This 2001 Ford ExplorerSportTrac & V6~4.0L~SOHC engine has 3 OxygenSensors; they are also known as HEGO\HeatedExhaustGasOxygen, H02\HeatedOxygen, Lambda\NarrowBand Sensors; as located below.
Sensor11+Sensor21, pic below, are between Rght+LeftManifolds & Rght+LeftCatConvertors, respectively.
Sensor12, pic below, is mounted in between the two collective\common\downstream RearCatConvertors.
All these Sensors are operationally alike & materially similar, excepting the longer or shorter 4WireCables.
A Bosch 15719 with 24i00 0m610 Long Cable+Plug is good to replace any Ford 4WireNarrowBand Sensor.
Each has a FordStandardPlug+4WireCable with Blk+Gra wires for the signal & Wht+Wht wires for a heater.
Each Sensors Heater element varies 3~9ohms & is used to decrease warmup time for the Signal element.
The upstream Sensor signals to the PowerControlModule\PCM are for ClosedLoop Air~Fuel Ratio control.
The downstream Sensor signal to the PCM monitors the CatConvertors & ensures Emissions compliance.
The PCM monitors+analyzes signal amplitude+frequency for FuelInjector control & setting TroubleCodes.
The 0.10~0.90vDC signals alternate every few seconds, responding to varying Lean~Rich Air~Fuel ratios.
An OBD2 scanner can be used to view\graph related codes & signals; I use OBDLink# MX+ & EX modules.
OxSensors degrade+fail with time or use; replace every 12Yrs\100kMiles to maintain engine performance:
these also often fail when their Cabling\Harness has been installed too near Moving or HotExhaust parts.
Driving with a failed OxSensor can eventually cause a CatConvertor to get clogged & an expensive repair.
Sensor replacement is relatively simple. Presoaking Sensor threads at the pipe bungs with penetrating oil for a few hours can ease removal; a MapGas torch can heat & break free excessively crusty bung threads. Nimble fingers also helps to disconnect+reconnect the wiring: Sensor11's plug is on the Engines rightrear, Sensor21's plug is above the Transmissions left ShiftCable, Sensor12's plug is on the Transmissions right.
Links To Related Info
Thanks go to the brave souls who've preceded me in similar adventures & freely shared their experience:
- https://web.archive.org/web/20170701123657if_/http://www.partsgeek.com/mmparts/the_ultimate_guide_to_the_oxygen_sensor_for_dummies.html
- https://web.archive.org/web/20200907142452if_/http://secure.lambdapower.co.uk/TechNotes/Tech-1.asp
- https://web.archive.org/web/20200907135224if_/http://www.bosch.com/stories/40-years-of-bosch-lambda-sensor
- https://web.archive.org/web/20200907151720if_/https://www.freeasestudyguides.com/heated-oxygen-sensor.html
- https://web.archive.org/web/20200907151127if_/http://www.fuelinjectedford.com/page31.html
- https://web.archive.org/web/20130626102106if_/http://www.motorcraftservice.com/vdirs/diagnostics/pdf/obdsm109.pdf#page=24
- https://web.archive.org/web/20200822182035if_/http://troubleshootmyvehicle.com/ford/4.0L/testing-the-oxygen-sensors-1
- https://web.archive.org/web/20200822182408if_/http://troubleshootmyvehicle.com/ford/4.0L/testing-the-oxygen-sensors-2
- https://web.archive.org/web/20200822182457if_/http://troubleshootmyvehicle.com/ford/4.0L/testing-the-oxygen-sensors-3
- https://web.archive.org/web/20200910195723if_/https://www.ranger-forums.com/4-0l-ohv-sohc-v6-tech-33/how-many-o2-sensors-137557 OxygenSensor Locations
- https://www.ranger-forums.com/general-ford-ranger-discussion-15/downstream-o2-sensor-voltage-164365 OxygenSensor Diagnosis
- https://youtu.be/afio03Sv_MU?t=0 OxygenSensor12@RearTailPipe Diagnos
- https://youtu.be/QiA8uksEYHo?t=25 OxygenSensors Replace
- https://youtu.be/9QzD8_srbSM?t=1 OxygenSensors Replace
- https://youtu.be/7Rtw8jI9quA?t=40 OxygenSensor11@RghtManifold Replace
- https://youtu.be/3reiaSERIXY?t=162 OxygenSensor11@RghtManifold Replace
- https://youtu.be/BVUzDz6i_bw?t=24 OxygenSensor12@RearTailPipe Replace
- https://web.archive.org/web/20200907182450if_/https://www.explorerforum.com/forums/threads/how-to-install-new-upstream-o2-sensors.282979 OxygenSensor11+21@Rght+LeftManifolds Replace
- https://www.boschautoparts.com/en/auto/oxygen-sensors/premium-oxygen-sensors?partId=13117 OxygenSensor11+21@Rght+LeftManifold Bosch# 13117
- https://www.boschautoparts.com/en/auto/oxygen-sensors/premium-oxygen-sensors?partId=15716 OxygenSensor12@RearTailPipe Bosch# 15716
- https://web.archive.org/web/20201113152331if_/https://images.carid.com/walker/items/schemes/13-03880.jpg ExhaustSystem PartsList Walker
- https://www.google.ca/search?q=%2B%22walker+exhaust+50202%22&tbm=isch&ved=2ahUKEwi3vKPu6P_sAhVBUM0KHTvNA4kQ2-cCegQIABAA&oq=%2B%22walker+exhaust+50202%22&gs_lcp=CgNpbWcQA1DpxwFYu_gBYK79AWgBcAB4AIABtgKIAYMpkgEIMC4yNS4zLjGYAQCgAQGqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=_aOuX_fJFsGgtQa7mo_ICA CatConvertors UpStream.47StateCompliant Walker# 50202
- https://www.google.ca/search?q=DEC+FOR9T20432&tbm=isch&ved=2ahUKEwiCxont9v_sAhX5Ap0JHdkPAhEQ2-cCegQIABAA&oq=DEC+FOR9T20432&gs_lcp=CgNpbWcQA1D-4BdYp5EYYNSVGGgBcAB4A4AB3AKIAeUYkgEIMC4xOC4yLjGYAQCgAQGqAQtnd3Mtd2l6LWltZ7ABAMABAQ&sclient=img&ei=qLKuX4LSOfmF9PwP2Z-IiAE&bih=612&biw=1366 CatConvertors UpStream.50StateCompliant DEC# for9t20432
- https://www.google.ca/search?q=walker+exhaust+53500&tbm=isch&ved=2ahUKEwjzpceq6__sAhV0A50JHbwfBLAQ2-cCegQIABAA&oq=walker+exhaust+53500&gs_lcp=CgNpbWcQAzoECAAQGFCDwCRYiNMkYOrfJGgAcAB4AIABhgGIAckGkgEDMy41mAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=lKauX_OLKPSG9PwPvL-QgAs&bih=612&biw=1366 CatConvertors DnStream.47StateCompliant Walker# 53500
- https://www.google.ca/search?q=Bosal+079-4172&tbm=isch&ved=2ahUKEwjQlJq67v_sAhUQX80KHU9eCsIQ2-cCegQIABAA&oq=Bosal+079-4172&gs_lcp=CgNpbWcQA1CDGVjNJWCLKmgAcAB4AIABqgGIAfIFkgEDMC42mAEAoAEBqgELZ3dzLXdpei1pbWfAAQE&sclient=img&ei=2qmuX9C_L5C-tQbPvKmQDA&bih=612&biw=1366 CatConvertors DnStream.47StateCompliant Bosal# 719-4172
- https://www.google.ca/search?q=DEC+FOR920586&tbm=isch&ved=2ahUKEwjwvc2r-P_sAhUJBs0KHUvgBqkQ2-cCegQIABAA&oq=DEC+FOR920586&gs_lcp=CgNpbWcQAzoCCAA6BQgAELEDOgQIABBDOggIABCxAxCDAVD0nhZYiLQWYPbAFmgAcAB4AIABmAGIAf8KkgEEMC4xMZgBAKABAaoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=OLSuX_DBH4mMtAbLwJvICg&bih=612&biw=1366 CatConvertors DnStream.50StateCompliant DEC# for920586
- https://www.therangerstation.com/forums/index.php?threads/diagnosis-of-a-clogged-catalytic-converter.188268 CatConvertors Clog