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Mass air flow sensor question and engine codes


kenwood guy
12-19-2011, 01:32 PM
hey guys.. i got a new issue with my 01 v6 4.3 silverado, the codes are p0101 p0300 p01416 and U1301 the codes that concern me are the first two. the service engine light is on and will flash only when im running the truck hard like going up a hill which means its miss firing i belive however, the truck is running fine with no loss of power no matter the rpm or load. i tryed cleaning the mass air flow sensor and it didnt fix the problem also, the cap and rotor and plugs have been replaced some 5k miles ago and was running ok with no lights on up untill now. the brand the parts were replaced with are borg Warner. i have heard on some trucks like the fords its better to stick with oe equipment and wonder if the parts are crapping out. i took the truck to a friend that has a snap on scanner and it was discovered that mutiple cylinders are miss firing and thinks its an issue with the mass air flow sensor and or plug wires ( they have yet to be replaced) i have a friend with a v8 silverado if i swap the maf sensor for testing should i expect his to work on mine??

thanks guy

j cAT
12-19-2011, 03:38 PM
the MAF may be defective or the throttle position sensor. when the throttle is opened a certain amount the maf expects to measure the correct air flow. your vehicle this is messed up. could also be a dirty throttle body..

I believe you have an air pump. if you do it is very possible the check valves which are part of the air injection pump system are defective. that means exhaust gases are going into the maf / intake. that will do it ...had that issue several years ago with my 1996 impala.

these check valves are good for 10 years even if you do not have alot of miles as the rubber breaks down..only get OEM check valves.

if you find the air pump is shot don't be surprised as I had to replace that to. air pump does not like exhaust gases in it...

kenwood guy
12-19-2011, 03:54 PM
the MAF may be defective or the throttle position sensor. when the throttle is opened a certain amount the maf expects to measure the correct air flow. your vehicle this is messed up. could also be a dirty throttle body..

I believe you have an air pump. if you do it is very possible the check valves which are part of the air injection pump system are defective. that means exhaust gases are going into the maf / intake. that will do it ...had that issue several years ago with my 1996 impala.

these check valves are good for 10 years even if you do not have alot of miles as the rubber breaks down..only get OEM check valves.

if you find the air pump is shot don't be surprised as I had to replace that to. air pump does not like exhaust gases in it...

Yea If i remember right it does have an air pump however I think it pumps it after the MAF sensor so it never sees it but yea i should check those check valves maybe if I disconnect the pump and hose all toghter and see if it goes away? Also there was one time when the throttle body was dirty awhile ago and it was noticable becuase the gas pedal would stick I would assume thats its clean but i guess its still worth checking out anyway.

j cAT
12-19-2011, 04:02 PM
Yea If i remember right it does have an air pump however I think it pumps it after the MAF sensor so it never sees it but yea i should check those check valves maybe if I disconnect the pump and hose all toghter and see if it goes away? Also there was one time when the throttle body was dirty awhile ago and it was noticable becuase the gas pedal would stick I would assume thats its clean but i guess its still worth checking out anyway.


yes when the pump/system works correctly the output surely does not get into the MAF ...when it screws up and works backwards the exhaust goes into the air intake duct after the air box air filter. this is where the air pump gets clean filtered air to pump into the exhaust to rapidly get those cat converters to remove excess hydo's...

if the duct/maf has black and water in it,,, the check valves and pump are really shot..

the pump also has an internal check valve...thats why I replaced all of it..

kenwood guy
12-19-2011, 04:29 PM
yes when the pump/system works correctly the output surely does not get into the MAF ...when it screws up and works backwards the exhaust goes into the air intake duct after the air box air filter. this is where the air pump gets clean filtered air to pump into the exhaust to rapidly get those cat converters to remove excess hydo's...

if the duct/maf has black and water in it,,, the check valves and pump are really shot..

the pump also has an internal check valve...thats why I replaced all of it..



wow well Ill disconnect it and see what happens would you happen to know if a maf from a v8 will work on a v6 silverado the duct size is the same i belive

j cAT
12-19-2011, 05:47 PM
hey guys.. i got a new issue with my 01 v6 4.3 silverado, the codes p01416 and U1301

thanks guy

forgot to mention p01416 is this air pump system failure the U1301 most likely was created when hooking up the scan tool..

j cAT
12-19-2011, 05:53 PM
wow well Ill disconnect it and see what happens would you happen to know if a maf from a v8 will work on a v6 silverado the duct size is the same i belive

don.t know about this swap idea. see if these two vehicles use the same part number from auto part supplier my guess is no.

what I do know is if the check valves are bad the maf will throw a code. disconnect air pump from the air duct and plug up the air duct hole. clear codes seeif the maf code gets thrown after you clean the maf with some maf cleaner..it only takes a little coating of exhaust goo to make the maf not see air flow.

kenwood guy
12-19-2011, 07:29 PM
forgot to mention p01416 is this air pump system failure the U1301 most likely was created when hooking up the scan tool..


would I see a problem in the idle also if what you say is correct? I maybe miss understanding you but I thought the air system was the air injection system during start up air is pumped into exhaust system to reduce emission during startup right?Mine is piped stright into the exhaust manafold after the air shut off valve. What would that have to due with the misfire?? p0300 code I disconnected a tube that went into the intake duct and drove around a bit and the light would start flashing again after awhile :(.... I also just found out the plugs used were actually AC delco and Everything else is BWD.. the one thing I didnt get replaced however were the plug wires I was told that this can also cause an issue.

kenwood guy
12-19-2011, 10:17 PM
don.t know about this swap idea. see if these two vehicles use the same part number from auto part supplier my guess is no.

what I do know is if the check valves are bad the maf will throw a code. disconnect air pump from the air duct and plug up the air duct hole. clear codes seeif the maf code gets thrown after you clean the maf with some maf cleaner..it only takes a little coating of exhaust goo to make the maf not see air flow.

ok well I was able to disconnect the pump altoghter However, this does not seem to be the problem. The service engine light went out but under heavy load the truck still seems to throw a misfire detected code.. If I cant get another MAF to swap and check I really dont know what to do:( I could try to replace the plug wires but what are the odds that its the problem?? My dad told me the truck could also have a compression issue and can explain why nothing seems to be working to correct the proplem and why it happens only under heavy loads.

j cAT
12-20-2011, 07:57 AM
ok well I was able to disconnect the pump altoghter However, this does not seem to be the problem. The service engine light went out but under heavy load the truck still seems to throw a misfire detected code.. If I cant get another MAF to swap and check I really dont know what to do:( I could try to replace the plug wires but what are the odds that its the problem?? My dad told me the truck could also have a compression issue and can explain why nothing seems to be working to correct the proplem and why it happens only under heavy loads.

the air pump is commanded on the first 5 min that the engine is started cold. when the check valves are leaking the exhaust gases will flow into the intake , until the engine is shut down. by removing the air pump from the air intake tube and plugging up the air intake tube with no air leakng into it at all and cleaning the MAF the resetting of the pcm/computer should not throw the maf code... the pump code will still show. the missfire code which is all cylinders are randomly missfiring should go away. if it don't check fuel pressure should be 60 - 66psi. anything below this is fuel pump or filter etc causing the p0300..

the other problem which can throw the p0300 would be a restricted exhaust. so exhaust back pressure would need be measured ..

you could have 2 problems ..maybe more .


with the pump code showing you have a failure for sure with the pump and check valves ..replace those parts ..

rev engine and see if you feel the exhuast comes out of the pump air inlet hose . if it does you have to spend some money ...

when my air injection failed idle was fine..power was reduced but not too bad. after all the engine needs air not exhaust for proper combustion. no/low air the carbon/cat damage will surely get going ..

96 impala has a high HP engine ..with your v6 any loss of power is going to show much quicker.

kenwood guy
12-21-2011, 07:57 PM
well I gave up and took the truck to the dealer it turns out it needs a new catalytic converter and they want a grand to fix it:( I asked if they if were sure this was the problem and said they would have to continue testing if it continues.... I have read that a misfire could mean that the Cat is toast but I have also read that if you keep driving with an engine misfire that it can toast the Cat too I didn't drive the truck too much after the code appeared all city driving whiten 15 miles or so for about a week. I'm gona try and replace it myself I wonder how hard it is?

j cAT
12-21-2011, 08:11 PM
well I gave up and took the truck to the dealer it turns out it needs a new catalytic converter and they want a grand to fix it:( I asked if they if were sure this was the problem and said they would have to continue testing if it continues.... I have read that a misfire could mean that the Cat is toast but I have also read that if you keep driving with an engine misfire that it can toast the Cat too I didn't drive the truck too much after the code appeared all city driving whiten 15 miles or so for about a week. I'm gona try and replace it myself I wonder how hard it is?

to test the converter or exhaust for restrictions which can cause the p0300 randommissfire /loss of power you measure the backpressure there is no guessing.

with the air pump failed this may have caused this.

a muffler shop can take care of the exhaust issue for much less. first you must fix the air injection system. not doing this first you will screw up the new cat.

kenwood guy
12-21-2011, 09:11 PM
to test the converter or exhaust for restrictions which can cause the p0300 randommissfire /loss of power you measure the backpressure there is no guessing.

with the air pump failed this may have caused this.

a muffler shop can take care of the exhaust issue for much less. first you must fix the air injection system. not doing this first you will screw up the new cat.


Yea about the air injection system... for some reason my truck has a history of this code it seems every time I go for smog since I have owned it I always have to deal with the check valves left or right bank how does the PCM know which bank?? I don't see a sensor by the valves. I know the pump turns on and off like its suppose to should I just replace all the air components?? I know those valves are expensive and are suppose to last a long time. But before my last smog I replaced one cleared the codes pass smog and was able to keep them clear after 2k miles or so only to have that code appear again(1416 or 1415 :(.... Im gona have the GM techs look it tomorrow and if they tell me a check valve is bad Im gona go crazy. And to be honest the 1416 code has been on since the last smog check which was over 7 months ago so I think your right. I also forgot to mention that the engine does have a pinging sound under heavy throttle ......But what explains code P0101?? --Mass air flow sensor circuit or performance problems... For what GM wants to charge me I might as well get that replaced too..

j cAT
12-21-2011, 11:49 PM
Yea about the air injection system... for some reason my truck has a history of this code it seems every time I go for smog since I have owned it I always have to deal with the check valves left or right bank how does the PCM know which bank?? I don't see a sensor by the valves. I know the pump turns on and off like its suppose to should I just replace all the air components?? I know those valves are expensive and are suppose to last a long time. But before my last smog I replaced one cleared the codes pass smog and was able to keep them clear after 2k miles or so only to have that code appear again(1416 or 1415 :(.... Im gona have the GM techs look it tomorrow and if they tell me a check valve is bad Im gona go crazy. And to be honest the 1416 code has been on since the last smog check which was over 7 months ago so I think your right. I also forgot to mention that the engine does have a pinging sound under heavy throttle ......But what explains code P0101?? --Mass air flow sensor circuit or performance problems... For what GM wants to charge me I might as well get that replaced too..

when the cat is restricted the engine will ping. the check valves go for 20.oo ea. the pump is about 240.oo...

with exhaust geting into the intake this will do damage over time.I fixed my check valve issues after a few days of creating the check engine lt coming on.

kenwood guy
12-22-2011, 12:16 AM
when the cat is restricted the engine will ping. the check valves go for 20.oo ea. the pump is about 240.oo...

with exhaust geting into the intake this will do damage over time.I fixed my check valve issues after a few days of creating the check engine lt coming on.

Yea now im paying for it... some lessons are more expensive then others... do you replace both when one goes out?? ill let you know what the dealer finds tomorrow

kenwood guy
12-23-2011, 12:33 AM
Yea now im paying for it... some lessons are more expensive then others... do you replace both when one goes out?? ill let you know what the dealer finds tomorrow


well it turns out they think all other codes appeared because of the bad cat and want to start with that.... at this point I plan on changing the cat and since im gong be messing with the exhaust system I'm thinking of replacing all the oxygen sensors too. I have read multiple posts that they should be replaced after 100,000 miles and my truck is sitting at 124,000. Also, I'm going to remove the mass air flow sensor completely and inspect it with a magnifying glass if it looks dirty still ill spray it down some more if not, Ill see what happens with it after the cat and check valves are replaced. you say the Pump itself has a check valve? ill follow your test procedure and see if that's bad too

Thank you for your insight and advice :smokin:

j cAT
12-23-2011, 10:07 AM
well it turns out they think all other codes appeared because of the bad cat and want to start with that.... at this point I plan on changing the cat and since im gong be messing with the exhaust system I'm thinking of replacing all the oxygen sensors too. I have read multiple posts that they should be replaced after 100,000 miles and my truck is sitting at 124,000. Also, I'm going to remove the mass air flow sensor completely and inspect it with a magnifying glass if it looks dirty still ill spray it down some more if not, Ill see what happens with it after the cat and check valves are replaced. you say the Pump itself has a check valve? ill follow your test procedure and see if that's bad too

Thank you for your insight and advice :smokin:

with the air pump the internal check valve rubber breaks down, the pump still works fine. so just because a piece of rubber is bad the pump will need replacing.

post back how it all worked out.

cleaning the maf with CRC MAF cleaner at those small sensor wires is in most cases all that is needed. the honey combs with the air injection failure are usually blackened.

just remember not to touch those small sensor maf wires with anything.

kenwood guy
12-24-2011, 03:45 PM
with the air pump the internal check valve rubber breaks down, the pump still works fine. so just because a piece of rubber is bad the pump will need replacing.

post back how it all worked out.

cleaning the maf with CRC MAF cleaner at those small sensor wires is in most cases all that is needed. the honey combs with the air injection failure are usually blackened.

just remember not to touch those small sensor maf wires with anything.





Well I got the Cat replaced yesterday..... it was like truck had constipation WOW what a difference:cool: I could really hear the Flowmaster muffler I put in my truck a few years ago again... the truck no longer pings at full throttle and is more responsive the codes have be cleared for now... I went to my local muffler shop and got the work done for far less then what the dealer wanted... big shout out to the people at Valley muffler in west covina california great people great work for a great price:smokin:

4x4junkie
01-10-2012, 08:20 PM
i know this is a littlwe late of a response. recently i have been doing some research on the maf sensor and ait sensors, it appears on all the v8 engines from 1999 - 2005 the IAT is built into the MAF sensor, however on the v6 models they are seperate sensors so the wiring and plug would be different as well as the sensor.. only inputing this info for future readers.

j cAT
01-11-2012, 08:37 AM
i know this is a littlwe late of a response. recently i have been doing some research on the maf sensor and ait sensors, it appears on all the v8 engines from 1999 - 2005 the IAT is built into the MAF sensor, however on the v6 models they are seperate sensors so the wiring and plug would be different as well as the sensor.. only inputing this info for future readers.


I looked up this in the OEM shop manual and the v6 MAF does have a IAC built into it..

connector of MAF pins are A ground at the PCM, B IAC , C ground , D ignition voltage input , E MAF signal.

the IAC is the tan wire . goes to the VCM connector 2 pin 22.

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