How-To: Pull Diagnostic Codes OBD-1 Pre-1996 Fords

Poppy · 04-03-2010, 06:04 AM

Pull Diagnostic Trouble Codes (DTCs) From your onboard computer.
Your engine and transmission are computer controlled.
The computer uses sensors to tell it a number of different things and it controls actuators that push or pull mechanical levers (kinda). If one or more sensors aren't working properly, the computer goes "blind" and doesn't know what to do. If the computer can "see" but one of the actuators is broken and therefore can't follow the commands of the computer; the engine won't run correctly. The computer is preprogrammed with set values for each of its sensors, and each of its actuators. It will run a self check of all systems, like the space shuttle; it will compare its set value(s) to the value(s) it recieves from its sensors, and actuators. If any sensor or acutator is out of the "normal" range the computer will generate a "code." It will generate some codes on the fly, and others will be stored while you are driving. There is a simple method to "pull codes" out of the computer for one to use for diagnostic purposes.
Earlier versions of On Board Diagnostics OBD 1983-1995 can flash the error code to the dash board and can be pulled in one's driveway without any special tools.
Later versions of On Board Diagnostics OBDII some 1995, and pretty much all 1996 and newer, require one to use a code reader or scanner tool.
Some auto parts stores will scan your engine codes for FREE, you may want to call around. Some will scan OBDII but not the older (prior to 1996) OBD systems.
SO here you go...
How to scan FORD on board Diagnostic Trouble Codes (DTCs) in your driveway

HowTo Pull Codes 1983-1995 Broncos, Mustang, F series Trucks, Econolines, 302, 351 and more

dogsharks · 06-15-2010, 08:48 AM

Again, thanks for the education, I'll print this off and study it.

One thing you mentioned caught my eye, and both times when the 351W decided to die on me, I was shifting the automatic transmission. First time I had shifted from highway running to 4WD low range to climb a long driveway, second time I was climbing a long hill at around 45 mph and decided to manually shift into second gear just to give the motor a break, and shortly thereafter it began to cough. Thankfully on that second time I had crested the hill and was able to coast through the stop sign (after carefully looking both ways, no cars anywhere to be seen) and coasted all the way down to a nice safe place.

I'll read through the info and we'll be taking the Bronco out for a test run. After replacing what I did so far, she started up nicely as soon as the filter was full. I am going to cut that old filter in half just to look. It is all drained now as I've had it set out for a couple days to be sure.

regards,

Dogsharks

richierick · 10-16-2010, 08:42 PM

Poppy,

Finally thought that I found a solution to my problems with my 1992 Taurus on-board diagnostics, but was very disappointed that your link to the broncozone.com Driver Error failed.

What a waste of time.

electro · 10-16-2010, 08:55 PM

Rich, check back in a day or two. I'm sure either the link will work or supplemental information will be available.

Boghog · 10-17-2010, 08:21 AM

Here you go ,courtesy of Ford Fuel Injection.

Ford Fuel Injection » How To Run a Self-Test

richierick · 10-17-2010, 12:28 PM

Thanks Boghog. Your informative webpage is just what I was looking for. Have performed the EEC code tests.

The test codes I obtained were a little confusing, but I'm sure can be meaningfully interpreted. The codes were only three in number plus the cylinder balance test result:

111 System checks OK

172 (R,M) Oxygen sensor not switching - system is or was lean - Single, Right orr Rear HO2S - Fuel control (HEGO – Heated Exhaust Gas Oxygen sensor HEGO circuit indicates system lean (right side))

176 (M) Oxygen sensor not switching - system is or was lean Left or Front HO22SSS - Fuel control (HEGO – Heated Exhaust Gas Oxygen sensor HEGO circuit indicates system lean (left side))

Cylinder Balance Test read #9 No Problems

Are there two Heated Exhaust Gas Oxygen sensors, one on the left side(of what?) and one on the right side(of what?)?

If the system checks out OK, and the cylinder balance test showed no problems, then why would the codes, 172 & 176, for the HEGO have even registered?

I'm trying to resolve the problem with my 1992 Taurus, because I just failed a state emissions test due to high Nox emissions of 2708ppm actual versus 878ppm state mandated max limit. Just looking at the results that I received doing the EEC test, I don't understand why only HEGO results were obtained, since nothing seems related to Nox emissions. Would a HEGO sensor failure cause the Nox emission to read high like I have experienced?

If you can give me some held in understanding these EEC test results that I've obtained in light of the high Nox emissions failure result during the state inspection, would be appreciated.

Boghog · 10-17-2010, 02:32 PM

Well the heated O2 sensors are left for the left bank of cyls and right for the right bank of cyls.This way the PCM can monitor how each side of the engine is running.The 2 codes you supplied 172 and 176 are telling you that the left and right bank of cyls are running lean.Meaning not getting enough gas to meet the 14.1 ratio the computer is looking for.This is usually cause by a vacuum leak going to the intake,an example would be a cracked or disconnected vacuum hose.Sometmes the intake manifold gasket can loosed up from vibration and allow excess air to enter.because both of these leaks are after the MAF sensor the computer does not recognize them as added air to the system.This is also the reason that your NOX readings are higher than normal.Nox is a byproduct of combustion and is used to lower cobustion chamber temperatures in the quench are of the cyl through the EGR process.You might try spraying some carb cleaner around the vacuum lines and intake manifold and see if the RPM increases.If it increases look in that area for your leak.

richierick · 10-23-2010, 05:43 PM

Hello Poppy,

I was having a high Nox emmission output, ran the diagnostics as you suggested and got codes 172 and 176 for HEGO lean conditions right and left sides. I replaced both Oxygen Sensors, and drove the car about 25 miles, before trying to read the diagnostic codes again. Didn't get the codes 172 and 176 again, but I'm not sure what I did get. On the KOEO test, seems like I got 111, but it didn't repeat, and then appeared to receive some random numbers that didn't repeat either.

Poppy, how much driving is necessary before the cars computer will report the correct codes during the KOEO and the KOER tests?

Also, will reported codes always repeat a second time?

WHy would I receive a code 111 reported twice indicating system is ok, but also receive other codes that are also reported twice?

richierick · 10-23-2010, 05:54 PM

Originally Posted by Boghog

Well the heated O2 sensors are left for the left bank of cyls and right for the right bank of cyls.This way the PCM can monitor how each side of the engine is running.The 2 codes you supplied 172 and 176 are telling you that the left and right bank of cyls are running lean.Meaning not getting enough gas to meet the 14.1 ratio the computer is looking for.This is usually cause by a vacuum leak going to the intake,an example would be a cracked or disconnected vacuum hose.Sometmes the intake manifold gasket can loosed up from vibration and allow excess air to enter.because both of these leaks are after the MAF sensor the computer does not recognize them as added air to the system.This is also the reason that your NOX readings are higher than normal.Nox is a byproduct of combustion and is used to lower cobustion chamber temperatures in the quench are of the cyl through the EGR process.You might try spraying some carb cleaner around the vacuum lines and intake manifold and see if the RPM increases.If it increases look in that area for your leak.

Hello Boghog,

I decided to replace both of the Oxygen Sensors on my 92 Taurus. After doing so, I found a failed vacuum hose, only about 2 inches long, that goes to the EGR intake I think, and replaced it. Anyway, I will be returning to have the car retested for emissions on Monday.

Poppy · 10-23-2010, 05:55 PM

I don't know the answer to how long of a drive cycle does it take to clear the codes.
In the tutorial it tells how to clear the codes, by pulling the jumper as it is sending codes.

Remmeber that the first 111 is for the KOEO codes, the next set of codes that are displayed are Continuous memory codes. So you can get a 111 for the on demand codes, but still have codes stored in CM. The last set of codes would be your KOER codes with the engine running

Whenever you change a component that will affect the fuel air ratio, you are supposed to pull the negative battery cable for at least 10 minutes to clear the fuel trims. That will also clear out the CM codes.

I'd pull the battery cable and run it for a few days and see if the codes return.
Good job!

Poppy · 10-23-2010, 06:03 PM

Originally Posted by richierick

Hello Boghog,

I decided to replace both of the Oxygen Sensors on my 92 Taurus. After doing so, I found a failed vacuum hose, only about 2 inches long, that goes to the EGR intake I think, and replaced it. Anyway, I will be returning to have the car retested for emissions on Monday.

LOL.. I guess we were both typing at the same time.

The vacuum leak was most likely your problem, and the sensors were just reporting the leak.
In a '92 I think the O2 sensors were supposed to be changed every 30,000 miles or so, so I'd bet that they were over due.

richie65 · 10-26-2010, 12:33 PM

Hello Poppy,

This is richieric. Had to reregister on the website for some reason. Wouldn't recognize me. New ID is richie65. Wanted to let you know that my Taurus passed the state emission inspection Monday. It does look like the problem was that 2" piece of vacuum hose that had a 1" hole burned in it. If I had found the failed hose, I probably wouldn't have had to replace the O2 sensors, and saved some money. Oh well, I guess that's just life, huh?

Got one question tho. Altho I passed the emissions test, my Taurus emissions are still 300+ for the Nox. Max allowed is just 870. Why is my Nox reading 300+ on my 92 Taurus, while the Nox readings on my 95 Contour and my 95 Mustang only read less that 50?

Poppy · 10-26-2010, 06:59 PM

Hmm, That's interesting that you were ABLE to log on with a new screen name.
I'll talk to our admin about that. You may find that in the future you will only be able to log in with on screen name or the other.

Sorry... *I* can not help you with the NOX question. Hopefully someone else can. but don't be too surprised if some of these posts get deleted, because this is a HOWTO thread, not a help me with my problem thread.

biggestfordfan · 09-12-2011, 02:06 PM

is there anywhere one can buy the diagnostic machines to pull error codes? I mean regular folks, not certified mechs.

thanks in advance.

Dominick · 09-12-2011, 03:12 PM

Code readers

coloradohoosier · 01-14-2012, 03:01 PM

Thanks for sharing that, Poppy. Sitting in the driver seat reading codes is easier than standing in front of the van trying to do it with a cheap code reader, particularly for someone who hasn't done it very often and has trouble keeping 2 and 4 second pauses straight.

My 93 E250 5.8 did give me trouble reading the KOER codes though ---- it never gave me the four flashes to tell me to hit the brake, turn the wheel and hit the OD button. It just started sending codes --- and it sent one, 998 (hard fault present) that is supposed to come in the KOEO codes.

bootjack · 01-15-2012, 01:59 PM

great info... but for me the KOER test was a bust...... CEL and code reader immediately went to flashing a 998 code.... no engine ID code ...so now what?? CEL has been on for about 4 months but passed emissions test last week. KOEO test gave me a 111 code then a 224 under CM output.

92 Ranger, 2.3 L dual plug, EEC-IV, DIS...