Bad Codes

Blown88GT

Founding Member
Nov 13, 1999
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Palm Beach Gardens, FL
New Data 11/3/2011
KOER codes = 44,94
44 - Thermactor air system fault
94 - Air diverter solenoid circuit fault
Replaced bad TAB valve, no effect on problem.
Can't find any vacuum leaks.

Old Data 10/27/2011
81 - Air diverter solenoid fault, intake air control circuit fault/air injection diverter
82 - Air diverter solenoid fault or supercharger bypass circuit fault
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Been having problems getting my '88 back to roadworthy condition. For now, I'll skip over the fuel pressure problems which have been solved. Also ohmed the ACT & ECT, both within specs. Pulled the 2-10 pins apart, 1st time in 23 years, no corrosion but lubed with Corrosion Block

FYI, my '88 has the Ford Motorsports MAF conversion kit. 55mm MAF was just replaced with C&L 76mm MAF, starts & idled, didn't get chance to go further, because...

Car starts & runs fine idling in the driveway, vacuum is normal 20inHG. Upon mild acceleration it bucks/jerks, hesitates/stumbles. On a cool day, even after idling in the driveway for 30 min, it can take a few miles before the issue occurs. I can even get a couple pounds of boost depending on air/engine temp. Once the bucking starts, vacuum gage bounces all over between 0 & 20. Had this issue for 10+ years, never could figure it out, didn't happen all the time. Now has been getting much worse & car is undriveable.

KOEO O-codes are 67,81,82,95. C-codes are 29,95. 67 can be ignored because the clutch wasn't depressed. 95 means nothing because the fuel pumps are working properly. 81 & 82 indicated Air Diverter Solenoid & indeed the TAB solenoid was determined to be bad by pulling the TAB, connecting the MityVac hand vacuum & actuating with a 12V source. TAD was fine, EGR Regulator okay, too. TAB wouldn't hold vacuum for more than 5 sec energized or not. Seems to explain why it somewhat works. Installed new TAB from Ford dealer (same price as everybody online), same codes generated. I'm confused why the KOEO would generate the same codes after the TAB replacement.
 
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Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks.

Revised 28-Oct-2009 to correct code definitions and operation.

Code 44 RH side air not functioning.
Code 94 LH side air not functioning.

The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves. When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and the O2 readings increase. By toggling the dump valve (TAB), the computer tests for the 44/94 codes.

Failure mode is usually due to a clogged air crossover tube, where one or both sides of the tube clog with carbon. The air crossover tube mounts on the back of the cylinder heads and supplies air to each of the Thermactor air passages cast into the cylinder heads. When the heads do not get the proper air delivery, they set codes 44 & 94, depending on which passage is clogged. It is possible to get both 44 & 94, which would suggest that the air pump or control valves are not working correctly, or the crossover tube is full of carbon or missing.

Testing the system:
Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
 
Thermactor Air System
Some review of how it works...

Revised 17-Sept-2011 to add testing procedure.

The Thermactor air pump (smog pump) supplies air to the heads or catalytic converters. This air helps break down the excess HC (hydrocarbons) and CO (carbon monoxide). The air supplied to the catalytic converters helps create the catalytic reaction that changes the HC & CO into CO2 and water vapor. Catalytic converters on 5.0 Mustangs are designed to use the extra air provided by the smog pump. Without the extra air, the catalytic converters will clog and fail.

The Thermactor air pump draws air from an inlet filter in the front of the pump. The smog pump puts air into the heads when the engine is cold and then into the catalytic converters when it is warm. The Thermactor control valves serve to direct the flow. The first valve, TAB (Thermactor Air Bypass) or AM1 valve) either dumps air to the atmosphere or passes it on to the second valve. The second valve, TAD (Thermactor Air Diverter valve or AM2 valve) directs it to the heads or the catalytic converters. Check valves located after the TAB & TAD solenoids prevent hot exhaust gases from damaging the control valves or pump in case of a backfire. The air serves to help consume any unburned hydrocarbons by supplying extra oxygen to the catalytic process. The computer tells the Thermactor Air System to open the Bypass valve at WOT (wide open throttle) minimizing engine drag. This dumps the pump's output to the atmosphere, and reduces the parasitic drag caused by the smog pump to about 2-4 HP at WOT. The Bypass valve also opens during deceleration to reduce or prevent backfires.

Code 44 RH side air not functioning.
Code 94 LH side air not functioning.

The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves. When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and the O2 readings increase. By toggling the dump valve (TAB), the computer tests for the 44/94 codes.

Failure mode is usually due to a clogged air crossover tube, where one or both sides of the tube clog with carbon. The air crossover tube mounts on the back of the cylinder heads and supplies air to each of the Thermactor air passages cast into the cylinder heads. When the heads do not get the proper air delivery, they set codes 44 & 94, depending on which passage is clogged. It is possible to get both 44 & 94, which would suggest that the air pump or control valves are not working correctly, or the crossover tube is full of carbon or missing.


attachment.php




Computer operation & control for the Thermactor Air System
Automobile computers use current sink technology. They do not source power to any relay, solenoid or actuator like the IAC, fuel pump relay, or fuel injectors. Instead the computer provides a ground path for the positive battery voltage to get back to the battery negative terminal. That flow of power from positive to negative is what provides the energy to make the IAC, fuel pump relay, or fuel injectors work. No ground provided by the computer, then the actuators and relays don't operate.

One side of the any relay/actuator/solenoid in the engine compartment will be connected to a red wire that has 12-14 volts anytime the ignition switch is in the run position. The other side will have 12-14 volts when the relay/actuator/solenoid isn't turned on. Once the computer turns on the clamp side, the voltage on the computer side of the wire will drop down to 1 volt or less.

In order to test the TAD/TAB solenoids, you need to ground the white/red wire on the TAB solenoid or the light green/black wire on the TAD solenoid.

For 94-95 cars: the colors are different. The White/Red wire (TAB control) is White/Orange (Pin 31 on the PCM). The Green/Black wire (TAD control) should be Brown (pin 34 at the PCM). Thanks to HISSIN50 for this tip.

Testing the system:

To test the computer, you can use a test light across the TAB or TAD wiring connectors and dump the codes. When you dump the codes, the computer does a self test that toggles every relay/actuator/solenoid on and off. When this happens, the test light will flicker.

Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

Theory of operation:
Catalytic converters consist of two different types of catalysts: Reduction and Oxidation.
The Reduction catalyst is the first converter in a 5.0 Mustang, and the Oxidation converter is the second converter. The Oxidation converter uses the extra air from the smog pump to burn the excess HC. Aftermarket converters that use the smog pump often combine both types of catalysts in one housing. Since all catalytic reactions depend on heat to happen, catalytic converters do not work as efficiently with long tube headers. The extra length of the long tubes reduces the heat available to operate the O2 sensors and the catalytic converters. That will cause emissions problems, and reduce the chances of passing an actual smog test.


Now for the Chemistry...
"The reduction catalyst is the first stage of the catalytic converter. It uses platinum and rhodium to help reduce the NOx emissions. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2. For example:

2NO => N2 + O2 or 2NO2 => N2 + 2O2

The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas. For example:

2CO + O2 => 2CO2

There are two main types of structures used in catalytic converters -- honeycomb and ceramic beads. Most cars today use a honeycomb structure." Quote courtesy of How Stuff Works (HowStuffWorks "Catalysts")

What happens when there is no extra air from the smog pump...
As engines age, the quality of tune decreases and wear causes them to burn oil. We have all seem cars that go down the road puffing blue or black smoke from the tailpipe. Oil consumption and poor tune increase the amount of HC the oxidation catalyst has to deal with. The excess HC that the converters cannot oxidize due to lack of extra air becomes a crusty coating inside the honeycomb structure. This effectively reduces the size of the honeycomb passageways and builds up thicker over time and mileage. Continuous usage under such conditions will cause the converter to fail and clog. The extra air provided by the Thermactor Air System (smog pump) is essential for the oxidation process. It oxidizes the added HC from oil consumption and poor tune and keeps the HC levels within acceptable limits.

Newer catalytic converters do not use the Thermactor Air System (smog pump) because they are designed to work with an improved computer system that runs leaner and cleaner
They add an extra set of O2 sensors after the catalytic converters to monitor the oxygen and HC levels. Using this additional information, the improved computer system adjusts the air/fuel mixture for cleaner combustion and reduced emissions. If the computer cannot compensate for the added load of emissions due to wear and poor tune, the catalytic converters will eventually fail and clog. The periodic checks (smog inspections) are supposed to help owners keep track of problems and get them repaired.
 
TAD & TAB electrical connectors are keyed, however, their positions were reversed on the mounting plate, so I thought the TAB was bad, when, in fact, it was the TAD. Part numbers are the same except for A & B suffix; the bad valve was "A". All the codes said "Diverter". Pulled Diverter valve, put valve input to mouth & blow, vacuum changes direction of output. Works the way it's supposed to.
Easier to test Bypass Valve with engine running but could hear it actuating with hand vacuum.
It's possible the vacuum control lines were reversed because the solenoid valves were reversed.
Checked & rechecked, now, KOEO codes now 81 & 82.
Put hose on inlet to check valve feeding crossover tube. Able to blow through easily.
Looks like I have to check if the air pump is pumping air.

Will perform a new KOER in the AM.
-------------------------------------
1. Same codes this AM.
2. Tested Bypass Valve with engine running. 1st removed vacuum line, connected hand vacuum.
Start engine, air is being dumped through valve. Therefore, pump is pumping air.
Apply vacuum, air not dumped. Bypass Valve good.
3. Previously tested functioning of Diverter Valve when removed. Valve good.
4. Previously tested functioning of TAB when removed. TAB good.
5. Previously tested functioning of TAD when removed. TAD bad. Replaced with new TAD.

I'm running out of ideas.
 
Code 95 means the MAF conversion is not complete. MAF cars have an additional wire input from the EEC to the fuel pump relay under the seat. It monitors the pump and if it fails, generates that codes to help with diagnostic info.

So, if you are wondering why you have a code 95..that's the reason. To make it go away (if you want), you'll need to run a wire to the fuel pump relay and attach it to a specific pin on the EEC (i could did this up if you wanted to know)
 
Thanks for the info.

My MAF Conversion is Ford Motorsports P/N M,9000,A51, purchased from Lumberton Ford, 4/5/1993. Cost was $485, but the only way to do it in 1993.

I suppose Ford did not provide for a Code 95 in the kit? 88 SD's don't have a check engine light, so they didn't care about codes that won't show. Code readers were not available back then.

Right now, I've got enough problems just getting the emissions fault nailed down. Car is pretty much undriveable in gear at 20% throttle or above.

I think my next step is to pull the vacuum control line from the Bypass Valve & plug it, so air will be bypassed 100% of the time. What do you think? This might tell me it's the Diverter Tube.
My cats are not the original Ford units which were replaced under Factory recall. I sold the new Ford cats when they were replaced with high flow cats in 1994. Only about 15k miles since then.
 
The missing wire is part of the interior dash harness, so unless you replaced that, the kit does not address the issue.

Doesn't hurt anything. More of an FYI as to why you have a code 95.
 
That's not a very useful diagram. You need this one:

Diagram of the fuel pump wiring for 87-90 cars.
attachment.php


Notice that wire from the fuel pump relay goes to pin 19 on the computer: that's what gets missed in some Mass Air Conversions and sets code 95.
 
Could you explain why? It looks the same to me. Diagram is from 1988 Ford EVTM. I also have the original 1988 Ford Wiring Diagrams, many pages but too large to scan.
The entire 1988 Ford EVTM is on my website.


For me, the visual quality of the Ford diagram makes it hard to read. I have a 92-93 set of the Ford EVTM diagrams and they aren't any better. It may be just one of those personal preference things.
 
Thank you; now understood. Probably instead of "That's not a very useful diagram". it would have clearer to me if said: "That's not a very readable diagram."

I suppose if it's not readable, it not useful. Car is set aside until I can determine what is next useful step.

Next steps will likely be:
1. Remove the vacuum control line from the Bypass Valve dumping all the air, just to see if it runs OK.
2. Then remove the vacuum control line from the Diverter Valve & connect a constant vacuum line so all the air goes to the cats, just to see if it runs OK.

These 2 steps should confirm a plugged bypass crossover pipe. I have been looking at that pipe to see how to remove it. I can barely see the bolt on the passenger side & have no clearance for any kind of wrench. The driver's side is all but hidden. I may have to take it somewhere & let them do it, but just getting it there will be a real chore unless 1 or 2 above will work as a temporary fix.

I have yet to test the EEC outputs to the TAD & TAB, but all connectors removed so far are clean with no corrosion. Can't find any vacuum leaks anywhere, except the bad TAD solenoid which was replaced. I tested the TAD (Diverter) valve & it works perfectly.

Besides this problem has increased gradually in severity which leads me to believe it's not electrical in nature.
 
For 94-95 cars: the colors are different. The White/Red wire (TAB control) is White/Orange (Pin 31 on the PCM). The Green/Black wire (TAD control) should be Brown (pin 34 at the PCM). Thanks to HISSIN50 for this tip.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

...
I have found a discrepancy between your drawings and the Ford EVTM:
TAB to EEC (White/Red) is pin-51 (not pin-38) on EEC
TAD to EEC (Lt. Green/Black) is pin-11 (not pin-32) on EEC
However, the Ford Wiring Diagrams agree with your pinout.

I found this out when following your recommendations to monitor the toggling of the voltage when in test mode (KOEO). 12V is present but there is no toggling to ground on the TAB or TAD. This would explain why codes 81 & 82 continue to be given when the solenoid valves are tested good. This would also generate the codes 44 & 94 if both valves are not actuating. Ran out of time before attempting KOER, but it seems unnecessary until codes 81 & 82 go away.

It's either the wiring or the EEC. I still have the original SD EEC & can substitute it for the MAF computer. Supercharger belt is removed & air will draw through the entire system as if it weren't there.

To be continued...
11/10/11
My wiring harness pinout agrees with the Ford EVTM & NOT the Ford Wiring Diagrams.

Put the old SD computer back in & no more 81 & 82 codes. Bad A9S computer.
 
The Speed Density computers have a different pinout for the TAD & TAB signals. They are pins 51 & 11 on the Speed Density computers. The A9S Cali computer may be an odd duck and use the Speed Density pinout for the Thermactor Air system solenoids.
 
Thanks for the response. That may be true but I have 2 Ford drawings that don't match. Drawings show MAF with no notes pertaining to Cali or the other 49. EEC Module is shown with wire numbers only, no pinouts. Pinouts are only on the 60-pin connector.

Do you think an A9L could be substitued for an A9S? I might have to get my A9S rebuilt because I'm never going to find and A9S anywhere outside of California.

After examining the A9S, pins 11 & 51 go somewhere, they don't just stop at the connector. The circuit could be a duplicate of pins 32 & 38, but can't tell for sure by looking at it.

Might be worth looking in a junkyard, even for an A9L.

Got the SD computer back in with the MAP reconnected. SC belt is off.
It started & ran for few minutes before running out of time.
Computer is laying on the floor, TAB & TAD hanging.
Will have to work for now.
Next test KOER for any codes, i.e. 44 & 94. Then a road test.

New Info:
Spoke with tech support at Interactive Sytems & Technologies.
He said the problem could actually be the Ford Motorsport Adapter connector & not the A9S computer. Their MAF harness eliminates it & stops the bad codes for the Vss & the TAB & TAD, etc.
http://www.mass-air.com/Products.htm
 
With original SD computer installed, codes are the following:
KOEO - 11 (System OK)
KOER - 11 (System OK)
Must be the A9S computer. I'll be getting a reman. A9L (Cardone 78-4352) & new MAF harness. The C&L meter is new & the sensor is from the old 55mm MAF. Will try the new harness with the A9S just to see what happens.
No time for road test today.
 
Took it out for 3 road tests, after removing/installing various items.
1. SD computer installed in place of A9S. MAF not removed, but no place to connect it to, anyway.
2. SC plumbing removed, intake now inside fender, no filter.
3. Moved TFI back to distributor.

It's almost back to stock, except for the exhaust: hi-flow cats & Flowmasters
Still have part throttle hesitation & popping in exhaust directly under the console. Sounds like someone is setting off little firecrackers. This would indicate far too rich, even when cold. Air temp is about 80.

A. Could all these symptoms be a bad O2 sensor, i.e. carboned up?
B. Could one of the cats be clogged, forcing much to the other cat?

It's not as bad as when the supercharger was running, but as soon as throttle is opened (maybe 20%) & vacuum goes to 10-15, it's a Wild Mustang again. How do I tame this beast?
There are no bad codes at all.
Cylinder Balance Test reports all OK.
 
Bad O2 sensor will set codes 41/91 or 42/92.

Try putting some window screen in front of the MAF to see if there are any turbulence problems in the air intake. The stock 55MM MAF had one.