This comes from the original post I did on @2001LC S.A.I Mod post. In his post he shows a good way to update the filters on the pumps that prevents clogging up the system and the Cats. This obviously involves removing some of the components which are hard to get to. This is a great solution If you are already in there replacing a starter then its convenient. If not its a Pita imho.
I did a mod taken from the Toyota 5.7l engine that disabled the AIP altogether and is cheap. It does tap into the MAF THA pin to trick the AIP to not turn on at all, but you can also get your own MAF adapter and make this Mod plug and play. If you want to revert it back to factory then just remove the Mod wires and you'll be back to factory settings. This should work on the 4.7l, 4.6l and 5.7l Toyota engines.
What is the AIP system? and why is it used on the car? AKA SAIP (Secondary Air Intake System) or just S.A.I, SAI (Secondary Air Intake)
The AIP (SAIP or whatever else you wanna call it) is basically only run during cold engine start up. The EPA wanted even the small emissions during cold engine start up to be captured and not release those carbons to the environment and redirect it back into the engine to be burnt away. The AIP only runs until the engine/cat's warm up and then the AIP is disabled. So most of the time the AIP is run no more than 15 sec to 1-2 min or so, depending on the external temperature and how fast the Engine/Cats take to warm up.
To comply for that the car companies added a bunch of stuff like air pumps, diverters, tubing, etc. Obviously this stuff increased cost and added complexity to the system and adds to the maintenance. And when it fails due to years of mileage on our vehicles and hundreds of heat/cold engine cycles, it puts up these codes that we see.
What this modification does to the AIP System?
The AIP Mod basically disables the AIP during start up by telling ECM to not run the AIP at all. This can be done because the ECM sees Intake Air temp less than 41°F at cold start, this tricks the ECM into believing the Intake Air temp is <41°F only during startup. When the engine starts, the circuitry reverts everything back to normal.
How is this done?
This is done using a automotive Relay which is activated by the Starter relay. The Relay is connected to a 4.7k Resistor in line with the THA pin of the Mass Airflow Sensor (MAF) which reports Intake temps to the ECM. During startup before ignition start, the Resistor (via Relay) is engaged with the MAF making the ECM think the Air temp is <41°F. This disables AIP during start up (so the AIP is never turned on i.e. no pumps need to run at all). Once the engine starts the Relay removes the resistor in line from the MAF sensor which then reports the temperature as normal to the ECM. Please check out the circuit below and you'll get a better understanding.
Does this MOD work 100%?
Yes it does as long as your are not coming to this MOD after you get certain AIP Error codes. There are some error codes that occur after certain pump are stuck open due to debris (usually broken fan segments or filter) for this you will have to open and clean up the pumps, diverters, etc. to clear the codes. And then the MOD will work as usual i.e. it disables the AIP from the get go to not run at all. You should technically not see the issue again at least not for the vast majority of the AIP engine codes. There could be a small chance some other codes my be set, but those could be for other related reasons.
As an example, I was able to solve the following error codes - I got these codes and then implemented the AIP MOD and these codes never came back.
P0418 - Air Injection System Air Pump Malfunction
P2445 - Secondary Air Injection System Pump Stuck On Bank 1
Which years does AIP come into effect?
IIRC any vehicle year 2006 and above should have AIP incorporated per emissions regulations. So any 2006 and above Toyota LC/LX, Tundra, 4Runner, Tacoma. It effect all cars but we are just concerned with our Toyo's.
How long will this take?
If you got all the hardware and such. It doesn't take long to get this working. And the best thing is no need to remove any of the pumps, or any AIP equipment to get rid of this issue.
Is it legal?
So you are bypassing a system that is supposed to be used only about 2 min on a cold engine to collect the exhaust gases. So technically it is illegal. But was this stuff necessary to add more complexity to our vehicles. NO.. all this was done was for minor reduction of emissions. And because we LC/LX/Toyo 4x4 (Tundra, GX, 4Runner, Tacoma) owners love our vehicles and keep them way longer than normal 10+ years or 200k+ miles or more. If this issue is not addressed, It will eventually come up as its just a matter of time.
Will this effect current emissions?
So if your state does not do full inspection i.e. look under the hood for any modifications, wires and such you should be good. This does not effect your emissions as this only runs during start up and emissions are collected during running of the engine. Even if the state inspector sees under the hood you can hide the wires in different ways to where they will not suspect anything.
>>>>> THA PIN different per model and maybe year <<<<<<- Be careful and ensure you are looking at your vehicles year wiring diagram and find out your THA pin. The way I would do this is get your Vehicles EWD (Electrical Wiring Diagrams) and search for "Mass Air Flow" and make sure you are looking at the correct MAF for your vehicles engine type. Cause 4runners and Tundras have several different engines. Pick the correct engine searching the MAF which has the THA pin. For example below, this is for a 2006 LC/LX EWD where you can see the THA pin is the 4th pin colored Yellow/Black. This is the pin you need to tap.
Anyways enough talk here's the video on how you would bypass this thing -
If you need help let me know. I am also thinking of doing a DIY kit later on. It would be a plug and play solution no invasive cutting into the MAF THA wire. You can do that as well if you get the MAF connector. You can easily revert it back to stock that way.
Here's the instructions for those who would like to do it themselves -
DIY AIP Bypass instructions
My Tundras Forums post - Tundra's 4.7l engine AIP Mod bypass
I did a mod taken from the Toyota 5.7l engine that disabled the AIP altogether and is cheap. It does tap into the MAF THA pin to trick the AIP to not turn on at all, but you can also get your own MAF adapter and make this Mod plug and play. If you want to revert it back to factory then just remove the Mod wires and you'll be back to factory settings. This should work on the 4.7l, 4.6l and 5.7l Toyota engines.
What is the AIP system? and why is it used on the car? AKA SAIP (Secondary Air Intake System) or just S.A.I, SAI (Secondary Air Intake)
The AIP (SAIP or whatever else you wanna call it) is basically only run during cold engine start up. The EPA wanted even the small emissions during cold engine start up to be captured and not release those carbons to the environment and redirect it back into the engine to be burnt away. The AIP only runs until the engine/cat's warm up and then the AIP is disabled. So most of the time the AIP is run no more than 15 sec to 1-2 min or so, depending on the external temperature and how fast the Engine/Cats take to warm up.
To comply for that the car companies added a bunch of stuff like air pumps, diverters, tubing, etc. Obviously this stuff increased cost and added complexity to the system and adds to the maintenance. And when it fails due to years of mileage on our vehicles and hundreds of heat/cold engine cycles, it puts up these codes that we see.
What this modification does to the AIP System?
The AIP Mod basically disables the AIP during start up by telling ECM to not run the AIP at all. This can be done because the ECM sees Intake Air temp less than 41°F at cold start, this tricks the ECM into believing the Intake Air temp is <41°F only during startup. When the engine starts, the circuitry reverts everything back to normal.
How is this done?
This is done using a automotive Relay which is activated by the Starter relay. The Relay is connected to a 4.7k Resistor in line with the THA pin of the Mass Airflow Sensor (MAF) which reports Intake temps to the ECM. During startup before ignition start, the Resistor (via Relay) is engaged with the MAF making the ECM think the Air temp is <41°F. This disables AIP during start up (so the AIP is never turned on i.e. no pumps need to run at all). Once the engine starts the Relay removes the resistor in line from the MAF sensor which then reports the temperature as normal to the ECM. Please check out the circuit below and you'll get a better understanding.
Does this MOD work 100%?
Yes it does as long as your are not coming to this MOD after you get certain AIP Error codes. There are some error codes that occur after certain pump are stuck open due to debris (usually broken fan segments or filter) for this you will have to open and clean up the pumps, diverters, etc. to clear the codes. And then the MOD will work as usual i.e. it disables the AIP from the get go to not run at all. You should technically not see the issue again at least not for the vast majority of the AIP engine codes. There could be a small chance some other codes my be set, but those could be for other related reasons.
As an example, I was able to solve the following error codes - I got these codes and then implemented the AIP MOD and these codes never came back.
P0418 - Air Injection System Air Pump Malfunction
P2445 - Secondary Air Injection System Pump Stuck On Bank 1
Which years does AIP come into effect?
IIRC any vehicle year 2006 and above should have AIP incorporated per emissions regulations. So any 2006 and above Toyota LC/LX, Tundra, 4Runner, Tacoma. It effect all cars but we are just concerned with our Toyo's.
How long will this take?
If you got all the hardware and such. It doesn't take long to get this working. And the best thing is no need to remove any of the pumps, or any AIP equipment to get rid of this issue.
Is it legal?
So you are bypassing a system that is supposed to be used only about 2 min on a cold engine to collect the exhaust gases. So technically it is illegal. But was this stuff necessary to add more complexity to our vehicles. NO.. all this was done was for minor reduction of emissions. And because we LC/LX/Toyo 4x4 (Tundra, GX, 4Runner, Tacoma) owners love our vehicles and keep them way longer than normal 10+ years or 200k+ miles or more. If this issue is not addressed, It will eventually come up as its just a matter of time.
Will this effect current emissions?
So if your state does not do full inspection i.e. look under the hood for any modifications, wires and such you should be good. This does not effect your emissions as this only runs during start up and emissions are collected during running of the engine. Even if the state inspector sees under the hood you can hide the wires in different ways to where they will not suspect anything.
>>>>> THA PIN different per model and maybe year <<<<<<- Be careful and ensure you are looking at your vehicles year wiring diagram and find out your THA pin. The way I would do this is get your Vehicles EWD (Electrical Wiring Diagrams) and search for "Mass Air Flow" and make sure you are looking at the correct MAF for your vehicles engine type. Cause 4runners and Tundras have several different engines. Pick the correct engine searching the MAF which has the THA pin. For example below, this is for a 2006 LC/LX EWD where you can see the THA pin is the 4th pin colored Yellow/Black. This is the pin you need to tap.
Anyways enough talk here's the video on how you would bypass this thing -
If you need help let me know. I am also thinking of doing a DIY kit later on. It would be a plug and play solution no invasive cutting into the MAF THA wire. You can do that as well if you get the MAF connector. You can easily revert it back to stock that way.
Here's the instructions for those who would like to do it themselves -
DIY AIP Bypass instructions
My Tundras Forums post - Tundra's 4.7l engine AIP Mod bypass
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