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check engine codes


New Member
March 25, 2009
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City, State
Year, Model & Trim Level
'94 XLT
I just recently had the codes checked because of a check engine light issue. Here they are.

172 Heated oxygen sensor indicates lean condition, right side
173 Heated oxygen sensor indicates rich condition, right side
176 Heated oxygen sensor indicates lean condition, left side
177 Heated oxygen sensor indicates rich condition, left side
186 Injector Pulse-width higher than expected
214 Cylinder identification (CID) circuit failure
327 EGR Valve Pressure Transducer/Position Sensor circuit below minimum voltage
332 EGR valve opening not detected

I first started noticing problems when I made a long road trip, after about 3 hours the engine would start sporadically missing at highway speeds ~70 mph, it did get progressively worse to where there was constant missing (after 5-6 hrs of continuous driving), engine would only fire on all cylinders when you would you would do a quick acceleration, when let off to cruise would start missing again. It also continued to miss at idle and lower speeds at this time. I figured must have just been a bad spark plug, checked them before my return trip and all looked like to be in great condition. Engine started fine and ran normal when started for return and again about 3 hrs into driving starts missing again, stopped for half hour or so started up again no missing about 2 hrs later starts missing again. Also had about a 25-30% reduction in my fuel mileage.

Anyone have any thoughts and ideas on where to start? Is it just some bad oxygen sensors or is there a bigger problem here?


Explorer Addict
December 27, 2001
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City, State
Spanish Fork, UT
Year, Model & Trim Level
92 XLT and '87 Bronco II
Is it just some bad oxygen sensors or is there a bigger problem here?
maybe and maybe. codes by themselves can't tell us exactly what's wrong. Codes only provide a reasonable place to start diagnosing.

SOP with EEC-IV codes is to resolve KOEO codes first. If I assume that you didn't run the KOER test, so that these codes are from the KOEO test, then the only code on there that my code list indicates can be a KOEO code is the 327. The other codes would be CM codes. So my first question to you is: was the 327 a KOEO code (before separator pulse) or a CM code (after separator) or both? If you aren't sure how to distinguish between KOEO and CM codes, review my notes on pulling EEC-IV codes thread in the EEC-IV forum.

After resolving the KOEO codes, one is supposed to then turn to resolving KOER codes. At this point, I'm assuming you haven't attempted the KOER test. If this is true, review the instructions, so you'll be ready for this test once we resolve the KOEO codes.

At some point before tackling CM codes, I like to clear CM and see what code(s) come back up after a test drive. It isn't always useful or easy to troubleshoot codes that are "old" or "inconsistent".