How to Test O2 Sensors on '97?

I have a '97 Explorer, Control Trac, auto trans, and 4.0L OHV engine. I have error codes PO136 and PO141. I tried to test the O2 sensors as outlined in my Hayne's manual but am unable to manage to get a wire into the connector so I can test it. Is there a trick to this? Hayne's says not to backprobe the sensor itself. Am I going to destroy it if I stick a pin in the wire? Any other common problems that might cause these error codes besides the O2 sensors?

Reply to
Ulysses
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Use the correct size wire.

Absolutely will.

Common? Might be, (I'm not an expert on this engine) but the first thing is to check the connector make sure it is absolutely clean inside, and tight. Then test the sensor if you can, or replace it if you are unable to test. I've found this to resolve many O2 sensor problems.

Reply to
PeterD

Did you unplug and inspect the connector's pins? If not, that's a possible thing to do, and is easy.

Reply to
PeterD

Yes, I unplugged the connector and it looked clean and everything. Problem is I don't have a scan tool/code reader on hand so I won't know if it's fixed ;-) This particular code doesn't seem to make the CEL come on.

The car is gone today so I'll check the wiring from the connector up to wherever it goes when it comes back. Maybe spray some contact cleaner on the pins.

I guess it's about time to break down and buy a code reader. I've looked at a few but apparently there is a lot of difference between a scan tool and a code reader. Plus, if I have to pay out some serious money (anything over $1 right now is serious) I would like to get one that will work with my '97 Explorer and also with my '99 Ranger. And I'd also like to get one that will read the three digit codes on my '91 and '92 Explorers. So far I have no idea if one tool will do all this or not. The people at the auto parts stores just seem to want you to buy whatever they have hanging on the wall.

Reply to
Ulysses

Odd, I thought it would. The O2 sensor is an emissions critical component.

Use a proper electronics rated cleaner, not brake cleaner! Many brake cleaners today are very hard on plastics, and will litterally melt the connector body! Get it at a better hardware store, or even Radio Sludge if one is nearby.

If you are going ot work on cars and trucks, a code reader is one of the most important tools in your kit. I have four, OK, I am an extremest, love tools. A good reader/scan tool will run between $100 adn $300, and of course you can spend a thousand on one easily. But you can get one that will give just the codes for well under $100, too.

That's any ODBII scan tool/code reader. ODBII has been (mandated) for all vehicles as of 1996 and later. There are some new systems (CAN) but generally that is not an issue, as ODBII scan tools today handle all the protocols.

Big bucks to get a single tool to do both ODBII and the older ODBI, easier to either just use a jumper (if they work in the 91/92 vehicles) or a seperate tool.

Yes, there are combination tools, but they are not cheap. Figure at least $250 to $350 for a combo tool.

Of course! Look online, Amazon is a possible place to get one.

Reply to
PeterD

Perhaps something is not working right then. At the time that I had the codes read I got the code for the O2 sensor but no CEL. A short time later the CEL came one but went off after I cleaned the MAF and replaced the air cleaner. I can't say for sure WHY the CEL was on because I was just guessing on what might be the problem. So far it always seems to be either the MAF or the IAC that causes it to come on. At least on the '97. It seems to be touchier than my '91 which never gets a CEL or any codes and is driven under the same conditions. I live on a dirt road so anything in the air intake system is always the first suspect.

Those connectors can be hard enough to get apart without welding the plastic with solvents ;-). In the old days I used Tuner Cleaner but it seems to have gone the way of the dodo. I think I saw some electronics cleaner at Auto Zone but didn't try it yet.

Well, there's part of my confusion--I read things like CAN but they don't have a clear discription of what that means, or why I would want one. I understand the ODBII part, sort of. My Hayne's manual tells how to read the codes on my '91 but says I need a "scan tool" to read the three digit codes. In my blissful ignorance it seems that all is well because there are no error codes and no CEL but there may be a bunch of horrible things going on that I can't see.

Reply to
Ulysses

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