Cel Comes On After A Few Minutes

Don't guess, dump the codes...

Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.





If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10




Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see Equus - Digital Ford Code Reader (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

mikestang63 said:

Thanks for the post. If you read my post that is why I said I am going to pull the codes and find out what is going on. Will do that tomorrow am. Oddly, the CEL did not light up on the way home.

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Just some help to get you on your way without spending a bunch of $$$.
The OBDI first gen computer uses a different scanning protocol than the OBDII cars. The OBDII scanner won't work on OBDI without some sort of extra widget..

re-read my Dump codes post....

WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What year is the car? the wiring changed several times, and the model year is needed to get you the correct test path.

i had the same problem with code readers. finally jumpered the wires as described and read it that way. much easier. code reader is a waste of money once you try it the paperclip way.

mikestang63 said:

so just take a small jumper wire from pin 46 (top right plug) to the stand alone gray test connector? Thats it? Man Im returning this POS scanner then. All it did was beep and light up. Couldn't get it to flash. Thought I was having a senior moment. lol

Not to go off on a different subject but if I trash the smog pump and the hoses, what I did in the past is simply cap off the pipe coming from the back of the engine with a piece of hose and a plug with a worm hose clamp, then take a small piece of hose and loop in on the two ports off the connector coming from the passenger firewall. I plan on getting rid of the cats and replacing it with some shorty headers and H pipe with O2 sensors. Then just get an 84.5 inch belt. Sound right?

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just like in jrichkers post. the red wire is basically a paper clip. put the clip in the self tester port as shown and the other end in that single port that is hanging right next to it off the same wire harness, shown in pic above too. turn off everything in the car. turn key on but dont start it. put it in neutral and sit back in the drivers seat. it will prime the fuel pump as normal then you will hear it run all the tests under the hood. solenoids will click and such. will flash fast at first to show test in progress, then the code flashes are slower. count the flashes. have a paper and pen ready. you will see the pattern. write them all down and post back. this is koeo tests. next start the car after you are sure there are no more non running codes. it will rev and do alot of tests. wait and write the codes. then stomp the gas once so it goes to 2500 rpm. this will start the cylinder balance test. wait for it then write the codes. the last one will be single number codes (you want code 9 here), the rest are double number such as 11 or 43...

i too have a useless code reader... non returnable they say

mikestang63 said:

so just take a small jumper wire from pin 46 (top right plug) to the stand alone gray test connector? Thats it? Man Im returning this POS scanner then. All it did was beep and light up. Couldn't get it to flash. Thought I was having a senior moment. lol

Not to go off on a different subject but if I trash the smog pump and the hoses, what I did in the past is simply cap off the pipe coming from the back of the engine with a piece of hose and a plug with a worm hose clamp, then take a small piece of hose and loop in on the two ports off the connector coming from the passenger firewall. I plan on getting rid of the cats and replacing it with some shorty headers and H pipe with O2 sensors. Then just get an 84.5 inch belt. Sound right?

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Jricher will come in here and tell you to not take the smog equipment off. There's almost no point in it. Plus, you'll have a stinky exhaust. No bueno.

Also, anything below a legitimate scan tool from a company like Snap On, is a waste of time and money IMO. Throw that thing in the garbage and use the paper clip method or find someone with a Modis or Solus.

mikestang63 said:

Well, I can hear the darn smog pump bearings - like a grinding noise and I bet that is throwing off the CEL- so I either replace it or remove it. I've owned 3 fox body mustangs and none of them had the smog pump. We don't have smog checks here in FL. Can't really remember seeing one with the pump still on it. lol

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Taking off all your smog equipment will only cause a code.

EDIT: actually, it'll cause multiple codes and make the CEL come on.

The factory gauges are not accurate at all. Remember that the A/C condenser is mounted in front of the radiator, and that heats up with the A/C on. So it is slightly normal to see a small bump up in temperature while you are running your a/c because of the fact that your car is then pulling warm air through the radiator as opposed to just pulling cool air through without the a/c on.

mikestang63 said:

Different wrinkle today. On the way home after about 20 minutes the CEL came on for about 5 minutes, then went off on its own. The difference today was when I had the A/C on the temp gauge started to go up from the normal position of between the a and l on normal to half way on the gauge. When i turned the A/C off, the temp dropped down to about the m. When i parked it in the garage and came back out to the garage about 5 minutes later, it smelled almost like a burnt egg smell, or like something burning.

Question is, if the smog pump is going and or the cats are heating/clogging, would that cause the engine to run hotter and with the A/C on cause more load on the motor. The car has a fairly new modine radiator, water pump, and thermostat, The hoses look new and the radiator and overflow are both at the proper level. I do not see any weeping from the water pump, no coolant leaks. The clutch fan appears to be working. I just bought this car 3 weeks ago. I did a tune up and none of the plugs showed any evidence of oil or coolant, they all read fine. The car has 46k original miles.

I will pull the codes tomorrow after work and report back. Kind of sickening when you bought the car three weeks ago and these issues are popping up. I just brought the car to Ford for an oil change and they supposedly did a complete inspection and gave it a thumbs up with supposedly nothing wrong.

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pull the codes, replace the smog pump. flush and fill the radiator. the smog pump itself will not throw an engine code, it has no sensor to it. while the temp guage may not be the most accurate out there it is showing an increase of heat with the a/c on. this makes sense and points to the cooling system needing an inspection. it probably has alot of the original fluid in it and i bet thermostat too.

mikestang63 said:

ran the codes using the paper clip. amazing how it works.

KOEO- 2 codes

14 Two or more successive erratic Profile Ignition Pickup (PIP) pulses occurred, resulting in a possible engine miss or stall.
19 Failure in EEC internal voltage.

KOER codes- not sure if i read them correct. 11214191 ? I didn't know you were looking for 2 numbers as my other cars were all 4 numbers to a code.

12 Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too low) - ISC
21 Engine Coolant Temperature (ECT) sensor out of range - ECT ? it was fine during the test and 99% of the time
41 System lean - Fuel control
91 System running lean - Fuel control

cyl balance

9

Would any of these throw off a CEL?

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koer codes are 11, 21, 41, 91 they are all 2 digit codes.


lets ask for some help here. need someone way better than me at this. how about .... jrichker