Contour Enthusiasts Group Archives Forums General Troubleshooting Engine light comes on breifly usually at op temp

At operating temperature, I often see the engine light on the dash come on . It usually is there breifly like 10-30 seconds and then magically disappears.

About a year ago, it would come on maybe a minute after the car started and remain on for about another minute or so before disappearing.

Has anyone noted this type of behavior ? 95 SE with V6.

I suppose I could try sticking the multimeter into the
diagnonstic connector near the fuse box and play that game
since the computer must be working I'll probably get some kind of engine code and that may even point to the specific problem area the computer is getting missed sensor range from.

Then there is:
1) Doing this with engine off
2) Doing with engine on but cold
3) Doing it after engine at full operating temp.

It seems like since the light is kind of not associated with a detectable event that it'll be hard to reproduce the conditions making the light come on .

If the Check Engine light has been on, the computer will have stored error codes. Given the conditions under which you have seen the light, the problem is most likely an emissions-related component such as an O2 sensor or the EGR system.

You will have to read them or have them read. There are hundreds of possible codes each with its own diagnostic.

Your 95 can be read with nothing more that a paper clip and your eyes.

Here is a site that tells you how: http://dalidesign.com/hbook/eectest.html

Once you have extracted all codes, post them for assistance in deciphering them.

In many locations, chain stores such as AutoZone and Advance Auto parts will read your codes for free. If you take advantage of this service, WRITE DOWN THE CODES unless they can give you a printout.

Steve

My car does the same thing (usually only on highway) light comes on for 10-30 sec. then dissapears for a while (20 mins) and then re-appears. I am getting a 172 (rear o2 sensor not switching - lean) code.

I was also getting a 332 (EGR not opening) and 176 (front o2 sensor). This turned out to be a simple 1-hour procedure of cleaning out the EGR ports where they enter the upper intake manifold (behind throttle body) - they were plugged solid!

Check out GeoPappas FAQ on how to clean this:
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=trouble&Number=10673&page=0&view=collapsed&sb=5&o=7&fpart=1

ok .. with the engine warm (not quite up in the normal range - i had gone for about 25 min drive and it had set maybe an hour in the closed garage with maybe 62 deg ambient but very high winds ( ok -- maybe the coffee is strong and you dont need a weather report for rochester, ny !) .. yeah .. so

I plugged the jumper to 2 and then turned on the ignition .. you hear the fan kick on , then the 2nd one .. then they go to high , then they stop.
Then the engine light flashes very fast once.
Then it does a code train of 1,1,1 and repeats.
Then I get 1,1,7,2,1,7,2

I think the FORD intelligence my SETI receiver is picking up is a 172 code.
THIS IS the KEY ON ENGINE OFF (KOEO) TEST . Which according to the online site link you were nice enough to provide ( I saw it before in January - but had no computer running then to see these flashes).

it says:

172 (R,M) Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S - Fuel control

Which sounds exactly what the next nice fellow posted regarding cleaning out the EGR.. oh boy , now onto that site ! ... and boy I cant wait to dig in .. he claims its only an hour long job ... we'll see!

Neither Autozone or Advance auto had this (the throttle body gasket you need before starting the EGR cleanout operation) in stock - but I think Advance had it a little cheaper $2.30 - and beleived it would be in the store the next day.

Eric1,

I hate to break this to you, but I am still getting my 176 (front o2 sensor) code. Last week (before cleaning the EGR passages where they enter the UIM) I was getting 176 (front 02) AS WELL AS 172 (rear o2) and 332(EGR not opening). By removing the throttle body and cleaning the EGR passages I fixed the 332 and 172 codes.

In my case I believe the plugged EGR passages were messing up the ECC system and resulted in the 172 and 176 errors. As it is, I think that there is nothing wrong with my rear o2 sensors but maybe a bad front o2 sensor. I am told that there are actually four o2 sensors on the 2.5L (two on each exhaust manifold).

Anyway, I would definately check out the EGR passages(because they can get fouled up), but I wouldn't think that it would fix your o2 error. Please note that I am no mechanic. I could tell that there was carbon buildup on mine without actually taking the TB off - by looking through the TB (with the mass airflow sensor and air box removed).

u know , when i was replacing the air filter i had it out and i had a beer or two i think and i was wondering whats up in that hole and i think i stuck my finger up there.. i wonder if i poked out the mass air flow sensor.. that little metal string hanging in the middle of the passageway of the air intake.. so i cant recall if my finger hit the MAFS wire and like broke it or bent it .. is that possible to stick your finger in there and touch the wire when you have the air cleaner out ?

if so , they may be giving my 172 from out in the blue and then i can shell out what $100 for a new mafs wire which i dont know how to install .. but with 105k miles.. im sure its just the egr passageway and the good ole ford people wouldnt design the MASF sensor to be within reach of fingers when u have the air cleaner out . driving the ford is driving me to drinking.

I don't think you can just poke out your MAF sensor (I think it's on a steel bar), but I could be wrong. I don't know if it would affect your o2 sensor, but would doupt it. I would check behind the TB for buildup. Remove the MAF sensor and large rubber air tube where it connects to the TB and UIM (Upper intake manifold). You should then be able turn/open the throttle and look through it.

I think I'm going to take my car in to the dealer to test my o2 sensors, as there is probably a bad one that is bringing up my 176 code. I would suggest the same to you.

Concentrate on the codes at hand. You can't get to the MAF wire that easily.

Clean the EGR passages to have a chance to clear the 332. That error has other causes, but the clogged EGR passages is the most common cause.

Cleaning the EGR passages is very unlikely to affect the 172/176 codes.

The 172/176 codes are most likely due to worn out O2 sensors of there are no system vacuum leaks. If the sensors are over 50K miles, replace them anyway.

95 2.5L engines have only 2 O2 sensors. OBD-II systems starting in 96 have four.


Steve

Is it true that (on 95 2.5L) code 176 is FRONT O2 sensor and 172 is REAR O2 sensor?