Contour Enthusiasts Group Archives Forums General Troubleshooting What is the real definition to fault code 181?

Hi everbody, I'm new to this forum, but I'm pretty familiar with Ford fault codes,(my car is a 87 Mustang GT that I work on from time to time). One thing I have noticed is that not all manuals are created equal when it comes to fault code meanings. Case in point is my wife's Contour. It has some hesitation and stalling when cold. I replaced the plugs, wires, fuel filter, and air filter. It is a '95 2.0 and I have retrieved only one code, code 181. Between the Haynes, Actron, and online sources I have looked at, there are discrepencies. Does this code mean that the EGR valve or that the oxygen sensor is at fault? If anyone could give me the definition, or point me to a website that lists them, I would really appreciate it.

Come on, nobody knows? OK, here's what I do have. From the 95-98 Haynes Contour repair manual: "Fuel system-mixture too rich....check egr valve". From Haynes Automotive Emmission Control: "Adaptive fuel rich limit reached at part throttle, system lean, right side". From the Actron guide: "Hego sensor-voltage signal not switching: indicates "lean" during part throttle engine operation (bank #1). Plus, this site,[URL=www.mrfile.com/metroplex/eeciv.htmlmrfile.com[/URL] So, what could it be? Is the o2 sensor bad and unable to do its job, or is there a problem before the sensor with the fuel mixture?

It sounds like an oxygen sensor code. It is telling you that one of the oxygen sensors (bank 1 or the right one, in this case, the rear one) is reading lean at times.

If you are looking for a short answer as to why it is reading lean, there isn't one. It could be a defective sensor, but one of the most common mistakes of inexperience is to replace an oxygen sensor without trying to find out why it has bad readings. The manuals you have read from are suggesting some of the things that could be causing the problem.

You must now qualify the redings. You will need to scan the oxygen sensor ciruit to see what voltages you get. If your scanner only reads codes, then you will need more complete testers. The oxygen sensor readings are constantly switching or changing. An oxygen sensor generates a very low voltage in the absence of oxygen. The highest reading is 1 volt. Reading of less that .5 volts are considered lean readings. Reading of more than .5 volts are considered rich readings. Normally the reading will jump all over from one extreme to another and everything in between. A dead oxygen sensor will not switch at all. A lazy oxygen sensor will switch very slowly. If the readings switch but stay below .5 volts, the system is lean. If the readings switch but the readings stay above .5 volts, the system is rich.

The fact that only one sensor is reading lean indicates that there is something wrong with that bank or possibly that sensor.

A somewhat Mickey Mouse but effective method of qualifying the sensor is to swap the two (not very easy). If the problem changes with the sensor then it is a bad sensor. If the problem stays on the same bank, look elsewhere.

I do understand that there are no easy answers to why service codes come up. I was hoping that someone had the actual Ford manual with its definition of what that code meant. I decided to replace the sensor and the egr valve. Time will tell if it was the way to go, (it's only been an hour since I replaced the stuff), but I have had no cel since, and the car is running smoother. By the way, from what i've been reading, many of you are using the real-time programs on a laptop to check out your cars. Is there a comparable product for the EEC-IV?

You already have it. #1 bank oxygen sensor lean.

You're right, I have several definitions, but as you mentioned earlier, they are open to interpretation, (i.e. it could be the sensor, or it could be something else causing the sensor to read lean). That's one reason why I wanted the offical Ford definition of the code. I hoped that I might get more information from that source. Anyway, I have replaced the o2 sensor and the egr valve. The egr was original with 127K and the o2 had about 60K. It was time for replacement, and the car runs well with no cel yet. Thanks for your help.

Lifted straight from Ford's Diagnostic Trouble Code Summary Guide:
181 FUEL SYSTEM AT RICH ADAPTIVE LIMIT AT PART THROTTLE, SYSTEM LEAN (BANK#1)

Thanks for the reply.