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Check Engine light, multiple codes...argh

TippsTheFoo

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GP, MI
Year, Model & Trim Level
'00 XLT
Guys,

Really need some help with my '94 4.0 OHV Ranger. I've had it for a little over two years now with zero problems and now I've got one I can't seem to figure out.

First off, as back-story, I had my clutch replaced last month by a local shop. When I picked her up the check light came on, so I took the truck back and had them scan it. They said I needed a new O2 sensor and it'd be $120. I knew I could do this cheaper myself and I did.

I replaced BOTH O2 sensors for less than they wanted for one (part only).

Anyway, after replacing them (and clearing the code) the check engine light came back on. The codes I have are:

172
173
176
177

Lean and Rich on both sides. How? What else should I be looking at? I removed and cleaned the MAF and also searched for a vacuum leak (which I didn't find).

Help!

-Matt
 
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mikeinri

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Have you searched this site for these codes? Most likely, your answer is already here.

I haven't gotten one of those, so I can't help. I'm sure someone will, or take the codes to AutoZone, they can give you a detailed printout of what to check.

Mike
 
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TippsTheFoo

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The codes are both rich and lean codes from the O2 sensors, yet I've replaced them. It has me confused.
 
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MrShorty

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O2 sensor codes can be among the most difficult to diagnose.

Can I assume those are CM codes? My code list suggests that 176 and 177 can only be CM codes, but the other two could be KOER codes as well. Have you tried the KOER test? KOER faults are "hard faults" that exist at the time of the test. This can make them easier to diagnose. Of course, you have to make sure you've properly heated the sensors up before the test.

One thing I would do, especially if those are CM codes, and if it passes the KOER test, would be to clear CM and see if you get all those codes back or not.

You've replaced the sensors, so, for now, we'll assume the sensors themselves are good.

By the book, one of the first things they ask you to do to diagnose O2 sensor codes is to check fuel pressure. If you haven't done that yet, that might be the next thing I recommend.
 
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410Fortune

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have you cleared the codes to see if they re-appear?

Since this happened right after the transmission and exhaust was dropped (to replace clutch) check the wiring hanress to the 02 sensors, it is VERY likely that they pinched the wires between the transmission bellhousing and engine block, located behind the upper intake

The 02 sensor wires are held in place with a metal bracket that attaches to the top two trans to engine bolts, if they failed to hold these wires up out of th eway when they stabbed the engine then they would hang down and get pinched

NOT good news, I would return to them if this is the case and demand they fix it (a bit of work but not horrible, trans will have to be loosened from the engine and the wiring repaired (PITA to access the wires in that location unless you remove that part of the engine wiring harness so you can work on it

Have seen this before, have ALMOST done it myself a few times, you learn real quick

also possible the wires melted on the exhaust if they were not secured after the installation of the transmission, but my $$$ is on the pinched wires because you said CEL was on when you picked it up from them, new 02 sensors did nothing, and codes dont point to one single problem, but bad wiring to 02 sensors.

Also I guess its possible they crossed the 02 sensor plugs or did not get them plugge in fully
but the codes point to shorted wires (grounding out) so I suspect pinched
 
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TippsTheFoo

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410, are you talking about the O2 sensor wires or the harness wires?

I replaced the O2 sensors (unclipped the old from the harness, clipped in the new and put the sensors in) after the clutch work was done. Those wires (from the sensor to the harness) are free and clear.

But I just don't buy that this isn't related to the clutch work I had done. The truck was running perfectly when it went in and the minute I drove it away, this began. The response I got from the shop was, "Well, it's the O2 sensor because it's 14 years old, blah, blah." Well, after replacing both of them the issue is still here. Thus, my reluctance to take it back for troubleshooting/repair.
 
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wvfordaddict

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I just had new clutch put in yesterday in my 01 ranger, now my cel is on after about an hour of running, the o2 code is coming up when I ran the codes. did you ever figure out what the problem was with yours?
 
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410Fortune

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the wiring harness to the 02 sensors is thefirst thing I would check, if they pinched the 02 sensor wiring harness between the trans and engine it could be big trouble

Many times they just forget to re connect them, other times when they drop your exhaust they dont remove the sensors properly and they can damage the wiring to them...

Anyways bottom line is the 02 sensors have to be messed with in order to drop your transmission, the exhaust must come down....so if you had trans work done and immediatley get 02 sensor codes....its most likely the shops fault and IMO its likely they furabr'ed your 02 sensor wiring....
 
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mawrazen

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Atlanta, Ga
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94 Eddie Bauer
I've been fighting the same codes for years.

Usually happened after a few hundred hwy miles. I added an Aif/Fuel Guage to watch whats happening. Now I only get them when towing. I have tried everything this problem is the pits.

Someone please offer a fix that works. PLEASE!

:banghead:
 
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