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CEL NIGHTMARE HELP! p0491 code

82K views 172 replies 45 participants last post by  fmahjobi 
#1 ·
Hello Fellow Bimmer lovers..

Purchased my first 03 745li LOVE the CAR Runs perfect drives like a dream, however NOT going to PASS State inspection... :(

I am getting Check Engine Light about every 3 days after reset code P0491 this is the only code.

Already changed all Vacum lines ALL NEW to check valve on passanger side new check valve new secondary air pump all brand new still getting this dreaded code any other ideas would be GREATLY apperciated???

I have doubled checked all housed several times replaced every part I know to replace I did see someone replaced CCV's which I have not does anyone think I should??

Thanks Chris :dunno:
 
#2 ·
More than likely you have the same problem many 7 owners have - carboned-up heads, which prevent air from the air pump to circulate through them. It has NO EFFECT on how the vehicle performs, but it will fail emission testing. FWIW - repairing this will empty your wallet of approximately 7-12k dollars. Are you also getting P0492 codes? Usually you get both.

If you have a similar testing system as we do here in BC, you are allowed 1 readiness code not set and still pass testing. Sooooo.....if you reset your SES light and wait until the one last readiness monitor is not set (which will be the secondary air system), and then proceed with testing, you will pass.

If you have anymore questions, fire away. I have become somewhat of an expert on this problem, through extensive and painstaking research.
 
#13 ·
More than likely you have the same problem many 7 owners have - carboned-up heads, which prevent air from the air pump to circulate through them. It has NO EFFECT on how the vehicle performs, but it will fail emission testing. FWIW - repairing this will empty your wallet of approximately 7-12k dollars. Are you also getting P0492 codes? Usually you get both.

If you have a similar testing system as we do here in BC, you are allowed 1 readiness code not set and still pass testing. Sooooo.....if you reset your SES light and wait until the one last readiness monitor is not set (which will be the secondary air system), and then proceed with testing, you will pass.

If you have anymore questions, fire away. I have become somewhat of an expert on this problem, through extensive and painstaking research.
Roadfrog, please don't bs here, it's all ok with your heads, just go and replace old rubber hoses coming from sec air pump to checkvalves, worst case replace check valves too!!!
Damn how ppl can say that bs about heads???? Either they want you To spend money in the shop??? Or they fg stupid???
Ok here is the deal:
Let's imagine you have build up on your exhaust valves, if so the engine would run very very rough, bc there would be backpressure and probably your engine won't last 100 miles with clogged exhaust.
But even if so, it does not do anything to sec air system! It only blows air on cold start to reduce emissions bc o2 sensors are cold and therefore cannot regulate mixture, that's why you need more air to help cats to clean co2!
It only blows air in exhaust manifold down to cats, that's it! In other words if your cats are Alive and engine is dead, but sec air system is ok, it will pass sec air test!
 
#3 ·
RoadFrog thanks so much for the reply I have been reading alot and I was afraid I may get that reply as well...

Car has 89k on it runs perfect but I was afraid of that... I am only getting the one code as of now p0491

So basically remove the heads clean them all and do a valve job?

I also so another post a member stated there is some programming that some shops can do to bypass this check permenatly is that true? Can I send my ECM for programming? Just wondering this thing is killing me and I am for Sure not spending 7k only paid 15 for the car..

Thanks again another suggestions what about the CCV's think I should replace those that is easy and cheap repair... Also any cleaner I might be able to run to clean the Carbon like SEAFOAM or anything that may help?

Thanks Chris
 
#4 · (Edited)
So basically remove the heads clean them all and do a valve job?
Yes. Let me guess......you have blue smoke after a lengthy idle? This adds to the coking of the heads.

I also so another post a member stated there is some programming that some shops can do to bypass this check permenatly is that true? Can I send my ECM for programming?
Yes again. But you DO NOT need to send in your ECM. It's done in the vehicle. Apparently it's a DOS program from Germany and takes 2-3 hours to upload to the vehicle at a cost of about 500 dollars. Obviously, legalities of tampering with the Emissions Equip are at play here, so this stuff can be a little, "back door, hush-hush". I'll leave it at that.

Also any cleaner I might be able to run to clean the Carbon like SEAFOAM or anything that may help?
Nope! This coking is so hard that a honing tool is required and the passages are very hard to get to. The Seafoam and other snake oil stuff has been done to absolutely no success. Remember that the coking is in the exhaust side of the heads and is not exposed to fuel or intake.

So does your state allow one "readiness indicator not set" and still pass? This could be your way out. It was mine. I bought a Harbor Freight scan tool, reset the SES and waitied until the final readiness indicator (which happens to be the secondary air) was resetting and then inspection. You have about a 3-5 day window untill the SES sets.
 
#5 · (Edited)
Honestly dont see hardly any smoke but havent really just let it idle and kept a close eye on the issue really I will try that today when I get home from work let it idle in my garage with it open! lol

Any idea on where or how to get the software who to contact? I used to run MIL eliminators on my Cobra Mustang which had NO CATs on it what so ever straight pipes and I passed emissions for years no issues what so ever so not to worry about the legal side if you will but I do understand the nature of it...

I mean I know plenty of places to get inspected and JUST BUY a sticker but the damn light is WHAT bothers me the most staring me in the face for hours..

Does that not just burn you up staring at the light on in your car? I think we are allowed one readiness code will check into it to make sure but I believe we are and you are EXACTLY RIGHT my light comes on every 3rd day after reset... pisses me off everytime :(

Anyway thanks again for all the help and advise seems like BMW should have stepped in here if its SUCH a BIG Known issue and SUPER COSTLY REPAIR... WOW:mad:
 
#6 ·
c4love,

Please please please take my advice and dump that car as soon as possible. In about 5 months your gonna be able to set up magic shows behind that 7 and disapear through the smoke behind it. I'm telling you from personal experience. What starts as a p0491 will turn into a p0491 and p0492 and you will try to replace the whole secondary air pump system only to be out $1500 than the smoke will come. The problem came from whoever owned the vehicle before waiting 15,000 miles for an oil change. It ruins this car. If you dont' believe me do some research on this forum, but im doing you a favor now. I know she a beautiful brazilian girl with a fat ass, tan skin but she has aids. Don't get the sickness.
 
#8 · (Edited)
Any idea on where or how to get the software who to contact? I used to run MIL eliminators on my Cobra Mustang which had NO CATs on it what so ever straight pipes and I passed emissions for years no issues what so ever so not to worry about the legal side if you will but I do understand the nature of it...

I mean I know plenty of places to get inspected and JUST BUY a sticker but the damn light is WHAT bothers me the most staring me in the face for hours..

Does that not just burn you up staring at the light on in your car? I think we are allowed one readiness code will check into it to make sure but I believe we are and you are EXACTLY RIGHT my light comes on every 3rd day after reset... pisses me off everytime
Call all your local BMW Indies and ask if they have the program. The shop here that does it, gets the software from Germany and it sounds like lots of shops know about it. It will get rid of the check engine light ONLY for the secondary air. Your SES will still work for all other faults.

Please please please take my advice and dump that car as soon as possible. In about 5 months your gonna be able to set up magic shows behind that 7 and disapear through the smoke behind it. I'm telling you from personal experience. What starts as a p0491 will turn into a p0491 and p0492 and you will try to replace the whole secondary air pump system only to be out $1500 than the smoke will come
Not necessarily. I drive 100 miles a day and have had the P0491 and 492 codes for 8 months. Smoke is minimal and in fact, you don't even see it unless you really look for it - and even then, only after a very long idle (15-30 mins). No need to replace the secondary air system since it has no effect on the driveability. Get the software change and fall in love again. That said, everyones comfort level is different.
 
#9 ·
I had the same problem with my secondary air pump like a lot of these guys and some guy here experimented with something that dnt make sense but he said it worked so I went ahead and tried it and it worked my check engine light has .not come up since and its been 2 months since I did this and very happy so go to auto zone or orielys and purchase the Lucas or gumeout liquid for fuel injection cleaner for bout 8-10 bucks pour it in not on a full tank but when u have 20-30 miles before empty and pour in cleaner and fill with gas and clear code again and see wat happens I.did it this way and so far so good u have nothing to loose I mean 10 bucks its worth a try and my car has 115k miles on it running strong good luck
 
#140 ·
It works it works it works!!!



The dealership told me around $8,000 to fix the problem causing the p0491 fault, an indie I've used before said $5,000, my regular indie told me it had been $5,000 but they had figured out a way do do it for around $3,300. Taking Ricardo's advice, I figured "He's right, what's $10 if it doesn't work"

I picked up some Lucas fuel injector cleaner at Auto Zone, applied it to a mostly empty tank before fueling up, and then drove about 100 miles. I went into my indie and asked him to clear the codes for which I was charged $52.50, he did it reluctantly telling me all the reasons it wouldn't work and they needed to do a full diagnosis. It's been over a week now and the light has not come back on and I was able to pass the inspection so I could register my car.

THANK YOU THANK YOU THANK YOU RICARDO!!!
 
#10 ·
Thanks for all the replys an advise! I respect everyone's opinion!

Not quite ready to give up yet my car is much like roadfrog my car does not smoke at all really no blue smoke at all that I can see occasionally some white after long idel an it's very minimum you really have to look for it..


I really would like to find someone that could just reprogram the DCM unit to bypass this seems like a simple fix an with NO performance issues at all don't see the point in the code really seems like a ghost code for BMW to make 7 to 12k in repair bills that are not nessacsary but that's my opinion :)

What do mean Roadfrog by call around to Indy shops?? U lost me forgive my ignorance.. Do u mean just local BMW repair shops like not dealer shops?

Thanks again to all!
 
#172 ·
Hi there, can you please send me the info on the place to reprogram the DCM unit to bypass p0491 / p0492 please.

Thanks.
 
#14 · (Edited)
Roadfrog, please don't bs here, it's all ok with your heads, just go and replace old rubber hoses coming from sec air pump to checkvalves, worst case replace check valves too!!!
Damn how ppl can say that bs about heads???? Either they want you To spend money in the shop??? Or they fg stupid???
Ok here is the deal:
Let's imagine you have build up on your exhaust valves, if so the engine would run very very rough, bc there would be backpressure and probably your engine won't last 100 miles with clogged exhaust.
But even if so, it does not do anything to sec air system! It only blows air on cold start to reduce emissions bc o2 sensors are cold and therefore cannot regulate mixture, that's why you need more air to help cats to clean co2!
It only blows air in exhaust manifold down to cats, that's it! In other words if your cats are Alive and engine is dead, but sec air system is ok, it will pass sec air test!
OMG. I do NOT know where to start here.

OK.... First of all, the exhaust valves have nothing to do with this and I did not say anything about exhaust valves. It's the SECONDARY AIR passages in the heads! They are very small and coke up, especially if you have failing valves which push more carbon into them.

Furthermore, do you realize how many people here at Bimmerfest have replaced their ENTIRE secondary systems, including the "rubber hoses" you keep referring to? Y pipes, diverters, pumps, hoses, etc, ALL to no avail - the SES errors return. I realize you have only 13 posts and have perhaps not read alot of the info given here by others, but google/search it and see for yourself.

Also, regardless of what the sec system does (we all know what it does by the way)....if you have a fault code - or two in most cases, YOU WILL NOT pass emissions testing.

Lastly, DO NOT accuse me of BS'ing! I am in Law Enforcement, not vehicle repair, nor am I a vendor/sponsor. I have NOTHING to gain with this info.
 
#16 · (Edited)
Ok, I'm sorry, I just checked the design of n62 and they decided to blow the air into the combustion camera, so it does have passages between each other.Before they were injecting air into manifold, but injecting it directly into camera makes better combustion for sure. Good news it does not affect the engine, I'm wondering if you remove the check valve and clean the air port, thinking it gets clogged only in the beginning, but probably in every camera.... At least you will get good air injection in 4th and 8 cylinder, may be it'll be enough to pass?
But the main problem here is worn stem valve caps where the oil comes from into combustion camera, that's why it clogges the passages, it's not carbon buildup, but burned oil;((
But judging by number of posts is bot smart though;) if I post 100 posts about angel eyes or 22" rims, would it mean I'm technically good?;) I do have diploma from state polytechnic university in internal combustion engines, diesel major. 4.0 gpa. Perfect in solid works and autocad
 
#17 ·
N62B44: Glad you edited your last post before I replied - I was going to get pretty nasty! LOL. Yeah, it's a troublesome design. Apparently not only are extended oil changes to blame here, but the change in fuel formulations over the years (ethanol). Regardless, it is what it is and we have to do what we can - including fooling the SES light and getting through emissions testing....both of which I did.

Anyway...you and I are good now? LOL.
 
#21 ·
Please please please

can I have this info? I did valve seals leaving the heads on the car and shortly thereafter BAM both banks clogged. i have been looking at exactly for this and will owe you bigtime for the info on the website for the download. 2003-2005 landrover, with the bmw motors, has a recall that was titled "thermostat peramater reflash" after doing this the truck never again uses or monitors secondary air. There is no way I am tearing this thing back appart. its running way too good. :bawling:
 
#22 ·
Has the Dealer performed the "Recall 03V-240: E65/66 with N62 DME Reprogramming"? The following is the situation occuring in the campaign:

SITUATION
BMW AG has decided that a defect, which relates to motor vehicle safety exist in certain '02 and '03 MY E65/66 vehicles equipped with N62 engine. The defect involves programming of the digital engine management control unit.

Due to a DME software error, desynchronization of Valvetronic motors for engine bank I and bank II may occur, which leads to: engine rough running, "Check Engine" light illumination, misfire faults, and finally engine stalling.


There should be a round sticker located on the B Pillar of the driver door frame indicating this recall campaign was pefromed on your vehicle. If this has not been performed on your vehicle please start by having the DME updated to the latest version per the BMW "SI B12 07 03"
 
#23 ·
That recall was done already.

My issue is the 491/492 codes for clogged secondary air ports in the heads. this was caused by leaky valve seals. I have 420 and 430 too for cats. smoke is bad. If anyone can send me info on the software I would be ever so grateful. thanks in advance.
.
 
#24 ·
Regarding CEL nightmare help! Would someone please send me the information for the software to trick the OBD and by pass the secondary air flow codes 0491 and 0492. I am dealing with the same problem. I found a supplier on line, but his software wouldn't work on the 02 model 745i, and he stated they had not made the chip for our cars yet. This would be a big, big help for me. Thanks in advance.
 
#28 ·
Guys, I would also like to add my observations regarding this problem. I have an 04 745 that I purchased in October. The car has 120K miles. I also am having the P0491 code on a generic scannel and also have codes 2760 and 2768 on my peake scanner. On long idle 15-20 minutes will start to emit the smoke. Car runs fine with no other performance issues. So far I have replaced the secondary air pump, the y pipe and both diverter valves to no avail. I only get the P0491 and no other codes on the generic scanner. What is odd is that the peake scanner first detects the 2768 code (which BTW is not in the peake manual) when the 2768 code appears, it does not trigger the SES light. Later on when the 2760 code comes it eventually does trigger the SES.

Another interesting thing I noted (and I believe this to be significant) is that there is a high amount of suction from my dipstick tube and from the oil filler cap id I open up either when the car is idling. I also noticed when I was repalcing the y pipe and both valves I had removed the throttle body and could see there was significant amount of oil inside the intake manifold. This is very similar to when the E38 M62 motor has the ruptured OSV valve (PCV valve) on the back of the manifold plate on that engine. I have also replaced both the CCV valves and that has not changed the symptoms.

My guess is that the suction pressure present in the intake is causing oil to be blown into the intake valves and the "burned oil" going inot the exhaust it was is causing the clogging or "coking" that roadfrog refers to.

So, IMHO, I think if I can find the culprit as to why there is high suction in the intake that is sucking crankcase oil vapors into the heads then perhaps I can resolve my issue. Not sure if everyone is seeing this same suction thing. I know some have said they replace their valve guide seals and it was fixed. i can't help but think that perhaps in those cases they fixed whatever was making the crankcase not vent properly while having the engine apart doing the valve stem seals.

Couls it possibly be some type of intake manifold air leak? Not sure.. How about this.. Can all those that have similar issue right now check to see if they have high suction at their dipsticks and or oil filler caps while the motor is idling? In some cases when I remove the oil cap completely while idling, the engine has stalled. i do not think this is normal. At least on the E38 is is not.

regards, LarryD
 
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