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94 spitting codes


November 13, 2009
Reaction score
City, State
Mission B.C.
Year, Model & Trim Level
'94 XLT
First off, thank you Blacksheep Josh for the list of codes and their meanings, very helpful. I used the wire bridge trick and sat in my explorer for about a half hour making dashes on paper.This is what she told me.
335 O EGR Sensor voltage out-of-range
171 C Heated Oxygen sensor unable to switch, right side
172 R,C Heated Oxygen sensor indicates lean condition, right side
175 C Heated oxygen sensor unable to switch, left side
176 C Heated oxygen sensor indicates lean condition, left side
181 C Adaptive Fuel rich limit reached at part throttle, right side
186 C Injector Pulse-width higher than expected
189 C Adaptive Fuel rich limit reached, left side
332 C,R EGR valve opening not detected.

Okay, so first and last are EGR one for the sensor one for the valve and a bunch of stuff that (I'm no mechanic) could maybe caused by mister EGR valve failing? Options, opinions? I'm a carpenter not a mechanic lol.

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The EGR and O2 sensor codes may or may not be related. Usually I think the best approach on something like this is to track down the KOEO codes first. According to your list, the 335 is the only KOEO code, so I would start there.

One of the things that make KOEO codes easier to diagnose is that they are almost always electrical (because they are set while the engine is off). KOEO 335 normally points to a fault in the DPFE sensor circuit. As common as it is for the DPFE itself to fail, I would quickly check the connections and such to the DPFE for obvious faults. If nothing obvious comes up, then I would replace the DPFE.

Then, clear CM codes, test drive, and see if the O2 sensor codes come back.

Thank you for your reply and explanation, these things baffle me. I'll get a new DPFE and follow your instruction. It may take a few days (finances) but I'll post back either way. Thanks again.

I don't know if you have them in B.C. but get your DPFE sensor from Autozone, It's made by Wells / Duralast and is upgraded internally.

DURALAST #SU243 at Autozone.
AIRTEX / WELLS Part # 5S2046 at RockAuto

I replaced under warranty 3 plastic DPFE sensors in 2 months from O'Reiley's so I suggest avoiding them.

Okay, after some confusion on the phone regarding the shape of the electric connector (oval, "D" shaped, straight sides) as there are two differing connector styles, I finally acquired the correct unit. It is installed, on first test drive CEL didn't come on for about twenty or so minutes, roughness and hesitation are hone, she purrs like a kitten. Upon arriving back home I repeated the procedure for pulling codes only to find the same list minus the 335 code at the first part of the sequence. Are these old codes? Should I clear them?

I would disconnect the battery a while, 10 minutes maybe, then hook it up and run the engine at idle for a few minutes then take it for a drive at varying speeds and RPM. Come back and check KOEO and KOER codes. That way, you'll know for sure.

It sounds like you test drove it and at around 20 minutes the CEL came on.
checking the codes was the same minus the 335 code. If so, you still have problems that need repair.

To clear the codes connect the test jumper and run the test again, while it is flashing codes unplug the jumper, this will clear the code memory without having to disconnect the battery and having to reset the radio.

The other codes seem to indicate problems with the O2 sensors. I would suggest testing the sensors if you can before replacing them as they are not cheap.

Best of luck.