O2 Sensors (check eng light) | Ford Explorer Forums

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O2 Sensors (check eng light)

ashnme

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Joined
February 3, 2002
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City, State
Springfield MO
Year, Model & Trim Level
1996 XLT Explorer
I am looking for a easy way to check the O2sensors in my 96 5.0 Explorer.
 



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I don't know of an easy way to test them withought using a scan tool. Not a code reader, but a scanner such as a Snap-On 2500 or an OTC Pathfinder. I know these tools are far out of the range of most individuals (and mechanics) but they are the only way I know how to properly test an O2 sensor.
IMHO, if you have over 70k on your X and you think your O2 sensors are bad, replace them. It won't hurt anything and may save you some money in the long run.
 






Listen to Mike.... the absolute best way to check an O2 is with a lab scope or such...... beyond my means and I do this every day. I'd be hard pressed to take it for granted that the check money light is on because of the O2s but these sensors are sacrificial in nature anyway. Most European and some Jap makes even specify an interval for changing them out......
 






Right on with the O2's...replace them.
You'de be one of the few if that's all it is though.
What other symptoms are there (power/MPG loss).
:chug:
 






I found this last spring when I was having intermittent problems with my O2 sensor last summer. I found it very useful and he gives procedures for testing O2 sensors in and out of the vehicle.

http://my.engr.ucdavis.edu/~avsmith/o2sensor.html
 






Reading over the link you posted, I can see where some problems may come from. In the late '70s and through the 80s, some of the Europeans included a time elapsed indicator lamp to indicate that the lambda sensor was due for replacement - in the very broadest sense, lambda sensors are the equal of oxygen sensors, though the computations were handled differently by the computer. In the North American vehicle, the CEL indicates a sensor reading (any sensor, not just the O2) that reads outside it's preprogrammed parameters.

There is not a whole lot of sense in testing an O2 sensor in car with a DVOM. The scan rate and display rate of an affordable DVOM isn't sufficient to give a true indication of O2 sensor activity. Upstream sensors will switch rich/lean at least once per cylinder pulse. Even if there were an affordable analogue meter of sufficient input impedance for this test, I doubt that the mechanical needle could react fast enough to show anything more than an averaged reading.

While the tests as written will show a sensor that has suffered catastrophic failure (as in "it's pooched") it wont reveal a sensor that has become lazy and is at the end of it's service life.
 






This post and one regarding the EGR valve seems as though I could have written them!!
My 94 XLT is running "loud" and the check engine light is on. I know for a fact that neither the EGR or the O2 sensor has ever been changed. (100k on odometer)
Can anyone give me some pointers on changing both of these parts. Any help would be great!! Thanks.
 






I just replaced two 02 sensors (different locations) on my '97 5.0 after the check engine light came on. The local emissions shop showed the error "02 sensor slow response, bank one sensor one" on the OBDII. A parts store guy took a wild stab & sold me the wrong one, but we got it right the 2nd time.

"Bank One" is ALWAYS PASSENGER SIDE, and "Sensor One" is the first sensor below the exhaust manifold. Unfortunately, this one's up on top of the pipe & a nasty one to get at. But it can be done without dropping the pipe or moving anything. Don't forget to ****** the threads generously with a rust penetrant (liquid wrench, etc.) & let it sit for at least half an hour before trying to remove the old one.

Last, you'll need to reset the computer, either by disconnecting the battery for a few seconds, or reset it with an OBDII Scan tool (some code readers have a reset option). Next, complete the OBDII drive cycle which basically means drive it around town for a few minutes & then out on the freeway between 55 & 60 mph for at least 5 minutes. Hope this saves someone else 50 bucks and a few busted knuckles by not replacing the wrong sensor!
 






Bank one is always on the side that has cylinder 1 whether it be on the driver's side or passenger side. On all three engines available on the Explorer, that is always the passenger side. On something else though, it isn't necessarily so.

I heard that if you remove the inner fender liner and go in through the wheel well it is much easier. I have looked up at mine from underneith and it does look like a b!tch to get to. I haven't looked at it from the wheel well though.
 






Robert is correct. Bank 1 is ALWAYS the the bank where #1 resides, be it Ford Chev, Dodge or <insert foreign make here>. Sensor 1 will, naturally, be the first sensor the exhaust meets (closest to the motor).
 






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