Thanks esp. 5-90, & XJ4PLAY, & others -- O2 sensor problem fixed

I wanted to report back on a fixed O2 sensor problem. My original description of the problem--& all the great help I received--can be found on this thread: http://www.naxja.org/forum/showthread.php?t=66704&page=1&pp=15

Special thanks to 5-90 for help in testing the wiring. And special thanks to XJ4PLAY for translating 5-90's wiring explanation from 1997 wiring into 1996 wiring.

The good news: I was right all along, (sort of) that it was a problem with the wiring and not a problem with the sensors.

The not-so-great news: I actually wound up taking it to a dealership.

Why I took it to the dealership: Well, when I tested the wiring, I found that all the wires had good continuity, including the grounds. I couldn't tell what was wrong, & I couldn't get any other mechanics to take a hard look at the wiring.

So... the dealership was strangely good to me: They ran a ($90.00) diagnostic, & decided they agreed with me, that the sensors were fine, but something was buggy about the wiring. They said they'd take the $90 off any further work, once they found out what was wrong. They actually listened to me when I told them what testing I had done, and what symptoms I had recorded. Three days later they call & say the wires were all fine, but the eyelets (the little terminals that are soldered onto the ends of the wires) were bad.

That is why, when I tested the wires, they all seemed fine. I don't think I touched the eyelets with the test leads when I was testing. The eyelets/terminals were apparently broken part-way off, so that the O2 sensors were getting partial power but not full power--which explains why they sort of worked and sort of didn't. The mechanic said he uses a high-power headlight bulb to test these things, & that the bulb would light when he grounded it on the bolt (passenger side on engine block, near the heater control valve, above & behind the oil pressure sender), but that the bulb would not light when he touched the eyelets that were attached to the bolt.

The mechanic cleaned and re-soldered the eyelets, & everything seems to be fine, now.

The dealership's service manager discounted the $90.00 diagnostic fee & waived the $25.00 shop fee (for soldering, new harness tubing, etc.), so all I was left with was the three hours of labor it took for the mechanic to pinpoint the problem. The bill came to $269.00. I don't begrudge them the money, although I wish it hadn't taken them nearly 4 days to fix it. It is a shame I missed the problem, but now I know to be more thorough.

Thanks, everyone, for the help.

Were those eyelets on the ground end or the sensor end?

You're quite welcome. At least you saved them work, which saved you money. That's still important...

There's a reason I don't solder connections underhood tho - especially anywhere near the exhaust. All underhood connections are crimped onto clean wire, using clean terminals, and I seal them with heat-shink and silicone (or use watertight connectors) if I expect to submerge them.

You still found a lesson there, and you learned it without spending far more money (which was entirely possible.) Happy to be of help.

Eyelets were on the ground end, attached to the engine block with a nut. (circuit is grounded on the bracket for the oil pan dipstick, above and behind the distributor and/or oil filter, on the passenger side of the engine, grounded right on the block)

Also, for what it's worth, the dealer's electrician said he found the problem by probing the circuit with a test lead attached to a headlight. He said a headlight requires a strong 12 volts to light up, and that the O2 circuit also requires a strong 12v to fire up the sensor's built-in heater. A little LED type test light or even a voltage tester may not find the problem as well as a headlight. Some smart old-fashioned auto repair, there.

As for the soldering, I'm pretty sure he said he soldered them back together, and, now that you mention it, 5-90, I too would prefer to crimp those eyelets on & seal them as you suggest.

I've gotta replace a power steering hose soon, so maybe I'll look into it then.

Thanks again, all.

about the bolt where you ground the eyelets, does the dipstick bracket come off?

rooster87 said:

about the bolt where you ground the eyelets, does the dipstick bracket come off?

Click to expand...

I don't think so, I'm pretty sure that sucker is welded on there. I'm not near my Jeep right now, so I can't confirm that, but I'm pretty sure the only thing that's removable is the nut that holds the ground wires on. I'll try to post a picture in the near future, since I get questions about it all the time.

If you use a silicone based sealer on wire connections, make sure you get an electrically rated silicone. It's not that it will conduct, but common household silicone caulks and sealers use acetic acid, which is corrosive to the copper wire and can introduce corrosion to the joint. Mouser electronics is a good source for electronic components and supplies.