Code 44 without a code 94

Discussion in 'Fox 5.0 Mustang Tech' started by sln583, May 16, 2009.

  1. I have spent a couple of hours searching the forum on this and couldnt find a solution for this code on my 88 california 5.0

    KOER test is giving me a code 44, Secondary air injection system inoperative (right side). Code 44 and 94 together usualy mean the Thermactor system isnt working properly, but a 44 on its own seems to mean the secondary air is being diverted just fine on the drivers side but not on the passenger side. My understanding is the thermactor air going to the back of the cylinder heads is not registering with the O2 sensor on the passenger side. I have tested the TAB and TADs and they are functioning properly and the smog pump is putting a good amount of air. I evan went so far as to pull off the pipe going to the back of the cylinder heads and blow compressed air through it and found it was not clogged.
    At this point the only solution I can see to this code is that the passages in the cylinder head itself is clogged, preventing the thermactor air from entering the exhaust system. Am I missing something? Where exactly does the thermactor air go once it enters the back of the cylinder head and where does it exit into the exhaust? Has anyone ever had this problem before and any suggestions on how to fix it without removing the cylinder head from the engine?
    I know it only diverts when the engine is cold but having any trouble code is bugging me.
    The o2 sensors have less than 5000 miles and I had the stock heads rebuilt before this problem started.

    I have found some great info on this forum, including the following explanation of how the secondary air system functions.

  2. The codes 44 & 94 are not side specific. The best information I have is that difference in the two codes is where they inject the air. Code 44 is the TAB or bypass valve and 94 is the TAD or diverter valve.

    Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks.
    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.

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

    If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
  3. Jricker, your posts on this have been the most educational I have found and I would really apreciate your insight. I used your info,as well as the info from Charles Probsts book, Ford fuel injection and Electronic engine control, to arrive at my current theory that the passenger side head is blocked and not allowing air from the smog pump to reach the exhaust system on that side.
    I just redid these tests today and doublechecked my info to make sure of the results before I disagree with you.

    Probst lists code 44 as right side specific and code 94 as left side specific. I realize other code manuals do not, but I think his are accurate. He also lists code 41 and code 91 as left and right side specific. this had imortant implications when I experimented with the TAD valve.

    I experimented with my vacum guage and found this not to be true. I dont think the solenoids for the TAB and TAD are responsible for setting the code 44 and 94. I think the O2 sensors set these codes based on whether or not the PCM sees a lean condition when thermactor air is diverted upstream to the heads and into the exhaust system during KOER. When air is diverted down stream into the catalytic converters, this happens after the 02 sensors and the PCM has no sensor to detect this has occured.

    These are the experiments I ran to confirm this.

    As I mentioned earlier Im getting a code 44 KOER with everything connected and working as it should. I confirmed the TAB/TAD solenoids function with a vacum guage. During KOER, the solenoids applied Vacum when they where supposed to, also eliminating the possibility of a vacum leak anywhere in the Thermactor system.

    I then ran a KOER test with the TAD vacum line disconected. This would default the thermactor air downstream to the catylitic converter during the entire KOER test. this resulted in a code 44 and a code 94, as expeirienced by everyone that runs aftermarket heads not drilled for smog. As i said earlier, these codes are set by the oxygen sensor not seeing the air injected through the heads into the exhaust.
    Disconecting the TAB vacume line has the same effect, no thermactor air into the heads becase the TAB is defalting to venting the smog pump into the engine bay.
    Therfore only a blockage in the air passage could produce a code 44 without a code 94

    I got further comfirmation when I ran the KOER with vacum applied (With my trusty mightyvac) to the TAD valve through the entire test. this time I got a code 91 (HEGO indicates system lean (Left HO2S)) I understand this to be happening because the thermactor air is being routed through the head and into the exhaust system through the entire test and the o2 system is reading a lean condition the entire test from the extra thermactor air being present. I assume on a car with a properly functioning Thermactor system(without a blockage in the head somewhere like mine) a code 41(HEGO indicates system lean(right HO2S)) would accompany the code 91 under identical circumstances. Again, the only way a code 91 could occure without a code 41 is if there is a blockage.

    Does this theory hold water or is there some other explanation for the results I have gotten?
  4. Examine the diagram for the Thermactor Air System I posted, or crawl under you car and see for yourself. There is no plumbing in the system that splits the smog pump output between sides. It is either into both heads or into the catalytic converters. Therefore codes 44 & 94 are not side specific. Probst, as good as he is, missed that one.
    The O2 sensor codes are side specific since there is an O2 sensor in each side of the H pipe.

    A missing or open circuited TAB or TAD solenoid will set codes 81 & 82 respectively. However, if the TAB or TAD solenoid sticks and does not switch vacuum on and off, you can get the 44/94 code. That's why I say to remove the output hose from the TAB & TAD valves to check and see if the airflow changes directions when vacuum is applied to each control valve. Also check to see that the TAD & TAB output changes when the solenoid's computer control side wire is grounded.

    To resolve any questions about blockages in the air tube that runs between the heads, remove the tube and run a plumbing snake or coat hanger through the tube. You should be able to make it exit both ports. Check the heads to make sure someone didn't leave a plug in one of the air tube ports. Both heads are the same, the air tube ports are on the front and rear surfaces of the heads. The front side gets a plug and the back side is left open for the air tube. If someone wasn't careful, they could easily put the head on with the air tube port plugged and facing the firewall.
  6. There is squirt hole in the bottom of each exhaust port that feeds the thermactor air into the exhaust stream.
  7. Turned out to be a melted o2 harness on the pass side. No more code 44.
    Glad I didnt pull the heads off
  8. How does that affect your theory of operation on the codes being side specific?
  9. I think the theory is still sound. My right side harness was melted and a couple of wires had been spliced in. I think the Right side o2 wasnt able to switch enough for the computer to detect the lean condition caused by the thermactor air, only on the right side. Im not sure exactly why I wasnt also getting a code 41, it seems the O2 sensor was working just enough not to throw that code. Or maybe the code 41 requires the O2 to do something, and it wasnt.
    Maybe I can try blocking off the air passage on the back of just one of my heads and see if the code 44 trigers on its own.
  10. The O2 sensor cant detect a Lean condition and Loss of the Thermactor Air at the same time. If was actually a lean condition, then a Lean Code would have shown.
  11. On a side note, The only TAB code I know of is code 82. But there is nothing that detects the air being pushed into the atmosphere. So you only get a Circuit failure code. So the 02's have nothing to do with the TAB.

    The TAD on the other hand, if it goes bad it will throw code 81 in a KOEO, but will throw code 94 and 44 in the KOER since both banks are affected by the one solenoid. So 94 and 44 are related to the TAD air flow, which is monitored by the 02s on either bank, and not the TAB solenoid and where it pushes the air.

    This make the 94 and 44 codes side specific.
  12. My Bad, I was describing the loss of thermactor air as a lean condition, and this is probably not accurate.
  13. No argument here.I will attempt to confirm this hypothesis.
  14. I had to know, so I went out to the garage to remove all doubt abouy my theory. I warmed the car up, and then ran a KOEO and KOER. All tests passed with code 11. I then loosened the drivers side(I decided to use the drivers side (Code 94) as aposed to the passenger side (code 44) for 2 reasons 1. I have never gotten a code 94 before. and 2. the drivers side was easier to get at.) end of the thermactor crossover pipe from the back of the head and slid an index card in between to block the air coming out of the pipe and into the cylinder head, then I tightened down the bolt.
    I then ran the KOER again, this time I got a code 94, Left side thermactor inoperative.
    I removed the index card and ran the KOER and got a code 11 again.

    There is no doubt left in my mind that the Code 44 and code 94 are side specific.

  15. No problem with finding out for yourself. :nice:

    But my post wasnt a Theory. It was a Fact. :D
  16. I have alot of respect for jrichkers opinion and wouldnt contradict him without proof.
  17. I learn something new every day. I will definitely take some time to study the "why it works that way" conclusions that have been arrived at here. Thanks for the input.

    Joe R.
  18. Very smart guy JR is. I enjoy reading his posts.