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Emission code 44 but no Check Engine Light

13164 Views 10 Replies 8 Participants Last post by  jjandascog
OK this is strange. I am getting a code 44 (Thermactor air system not operational) but the CEL is not coming on. I made sure that the CEL works because it does light up on ignition start and the one time that I accidentally swapped plug wires.

I'm pretty sure that the Thermactor system is working because when I replaced the O2 sensor and before the sixlitre timing bump there was no code 44. As soon as I bumped the timing the code 44 came back but no CEL.

Question is: Since the CEL light does not come on but I get a code will it pass California emissions (granted the levels are OK?) Do the smog techs throw a code scanner to check things like this?
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I am getting the same code 44. But my CEL is on. Did you get yours corrected?
In my limited electronic experience, a 44 code don't always set a CEL light.
If you're sure that all the thermactor componants are good, check for a vacume leak at both of the two control valves. One is way in the back between the rear exhaust cross over and might be hard to find. The other is sorta close to the passenger side exhaust manifold. In fact, it is so close that the plastic valve it attaches to sometimes gets a hole melted in it which is hard to see without removing the valve.

Just as points of interest;
I removed all that crap off mine after it all started burning out and simply capped-off the vacume sorces for the valves.
I no point did I ever have a CEL light.
I did have a 44 code, no doubt from the the various and ongoing componant failures. After removing the system and plugging the vacume sorces, I cleared my computer and the code never came back.
Since all that, my truck still easily passes my Texas (dyno) smog test. And does it with only one cat.
It may or may not pass a California test but...The operator that ran my latest test said that his scanner never picked up any codes, old or otherwise. That kinda tells me that if my scanner don't pick nothing up, theirs don't either.

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I agree w DGR.
DTC 44 (KOER); Right Thermactor Inoperative; "...indicates a Thermactor Air System leak which could be anywhere from the smog pump up front to include EGR solenoiids over on the right inside fender liner and all the way to the back of the engine which is what you see in the photos. There is also a smog tube that runs along the passenger side engine below the valve cover which runs to the back of the FI plenum up to a Air Bypass Valve (plastic) crossing over to the cross-over tube (exhaust) which is connected to that and the CAT, check valve and tube below. the Thermactor system is designed to capture spent gases and ultimatley send them down to the CAT to burn off etc. If you look closely you'll see the chek valve and CO tube is pipe threaded, use some anti-seize and don't over tighten and when putting the valve on the tube, you don't need a gasket for the CO tube ends but rather just use some bearing grease which melts and forms a nice gasket seal. this is a tip from Steve83; gaskets burn off and go away after a while and you're back with another vacuum leak etc..."
Source: by my PAL, JKossarides at FSB

System Diagram in a 5.8
Source: by Steve83 (Steve, That dirty old truck) at

Secondary Air Injection system consists of a belt-driven Air Pump, single or dual AIR Diverter valve(s), an AIR Bypass valve, and AIR Bypass solenoids, air silencer/filter, Powertrain Control Module and connecting wires and vacuum hoses. The Belt-Driven Secondary Air Injection system provides either upstream/bypass air or upstream/downstream/bypass air. The number of these system configurations vary significantly with AIR Bypass and AIR Diverter valve combinations (Figure 179).

1. The PCM requires ECT, IAT and rpm inputs to initiate Secondary Air Injection operation.

2. The PCM provides one or more signals that enable one or more AIR Bypass solenoids.

3. The AIR Bypass solenoids control one or more AIR Bypass valves and/or AIR Bypass Diverter Valves in order to route secondary air depending upon the specific configuration.

4. The belt-driven Air Pump is operational any time the engine is running.
read more by Steve83

and how to test in my Site's LINKS
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I've checked and replaced all of the vacuum lines going to the TAB, TAD, FPR, EGR valves so I don't think that I have any vacuum leaks.

I know that the TAB valve works properly because it's dumping air through it when I do the KOER test. I haven't checked the TAD valve or check valves yet due to the location of these but that's next on the list.

I'll probably just try to have the thing smogged and see if it passes since I'm not getting a CEL.

I've read through the steps to diagnose problems with the air system but I had another thought. What if I were to remove the hose going directly to the CAT and then perform the KOER test to see if air eventually dumps through that hose? The thought is that if it dumps through the output hose then it is working.
ok try that.. you could have a break in that hose; rusted out line.. etc..
My FIRST suggestion would be to pull off the Exhaust Cross-Over tube on the back of the engine/cylinder heads and visually inspect the "Check Valve" that's thread in on top, it's in a difficult location to really get a good look at it.....mositure and heat over long periods of time can cause it to rust/burn thru.....code 44 is a vacuum leak some where in the system, changing the air stream from up to down from the EGR and out the CAT causing poor performance, like a miss and loss of power......

IIRC there are 2 - 1/2" inch bolts and YOU CAN get to it from underneath, put something under your back to prop you up closer so the reach isn't so long......I did it, though you may have to get the passenger side bolt from above or both.....PITA but the check valve only costs around $ can do a lot of damage to the valves etc. if you let it go and don't resolve it properly...

FYI, one of the EGR solenoids is obsolete, they were Mfg'd by Lectron in MI for Ford....facing from the passenger side looking in it would be the one closer in proximity to the engine.....should it happpen to be an EGR solenoid, I have a guy who can get hard to get parts.....mine cost $115.00 to replace but it was an OEM original.........

Get the issue resolved and don't take any chances with the smog Nazi's, why go thru the hassel dealing with them if it does fail....

Remember, Mickey Mouse belongs in lol

Good Luck ~ :thumbup
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I've checked and replaced all of the vacuum lines going to the TAB, TAD, FPR, EGR valves so I don't think that I have any vacuum leaks.

I know that the TAB valve works properly because it's dumping air through it when I do the KOER test. I haven't checked the TAD valve or check valves yet due to the location of these but that's next on the list.

I had a similar issue that turned out to be the vacuum line to the Thermactor Air Bypass Valve. No CEL, just a code.

Just because the Thermactor Air Bypass Valve is dumping air out through the TAB Exhaust Muffler does not mean the TAB Valve is working correctly. When the TAB Valve is working it is diverting air to the Thermactor Air Diverter Valve.

Well, at this point you know that your Thermactor Air Pump is working. I would start with the easy stuff and then progress.

1. First check that the two vacuum lines are connected to the Vacuum Reservoir (coffee can) and the resevoir is in good repair with no leaks on the bottom. Frequently the can leaks or the vacuum lines are accidentally knocked off.

2. Check the vacuum hose to the bottom of the Bypass Valve.

3. Check the vacuum hose to the Diverter Valve.

4. Check the vacuum hoses to the TAB/TAD Solenoids.

5. Then check your TAB/TAD Solenoids.

These are common easy to miss problems. Once these are ruled out all that is left is:

6. Thermactor Air Supply Hoses

7. One-way Check Valves

8. Main TAB/TAD Valves.
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Just had a smog precheck done at Pep Boys just because I was getting the code 44.

It passed with flying colors.


15MPH(1692 RPM)
HC - Max 115, Ave 51, Meas 33
CO - Max .63, Ave .12, Meas .01
NO - Max 986 Ave 301 Meas 161

25 MPH(1377 RPM)
HC - Max 95, Ave 37, Meas 25
CO - Max .82, Ave .09, Meas .03
NO - Max 846, Ave 241, Meas 236

Its odd that I get the code 44 and it still passes!!!

Now I just need to pay the man for a test only.
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i got problem new motor in same type (302 ) crate motor
it is pining not sure whats up
i did a OEM check and it reads with key on motor off code 11
with key on and motor on i get code 44 and 77
the motor dose not have a catalytic converter on it any more and now it has no air pump
vacuum is 17 psi at idle
old vacuum lines are removed or plunged

it has Edelbrock in take manifold and a K&N air system on it also

its not a lot of information on it but a mechanic / friend put it in for me while i was in Iraq sense I've been home I've spent 30 + days fiddle farting around trying to figure out between fixing all the things neglected the past year i was gone
please help I'm tired of poring money in to it to try hopelessly not fixing the pinging problem
ill try ti get the info on the motor and where it came from
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Have the same code on my 88 302, code 44. My TAB and TAD solenoids are isolated from vacuum but are electronically connected and the smog system removed with the air by pass plugged. I to am running 17 vacuum at idle.

Just installed new motor

Does anyone know what the ECU sees that triggers the code? Is it looking at resistance of the solenoid when it is commanded to function? I do not see any way the ECU has to read feedback as far as the TAB and TAD valves functioning themselves.
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