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I have a 2001 BMW 540 IT wagon. The check engine ...

Sent to BMW Experts July 13 2008 at 5:34 PM
   

I have a 2001 BMW 540 IT wagon. The check engine soon light has come on twice now about two days apart. The first time this was after 1000 miles running 10% alc. in the gas. I had the OBD scanned an it came up with P0491 and P0492 Bank 1 and 2 Secondary Air System . I purchased a Actron readr and today the same two codes appeared. I have reset them again and thelight is out... for now. The first question is what is the problem and could the cheap ( premium ) gas cause this. The second issue is that I need to drive this car 2000 miles overthe next week. Will this be a problem?

 

Optional Information:
2001 BMW 540 IT 5 Liter V8

Already Tried:
Read Codes and checked Gas Cap

Customer (name blocked for privacy)
Status:  Closed   Value:  $20
Answer
July 13 2008 at 5:46 PM (12 minutes and 33 seconds later)
         

Hello and welcome to justanswer.com

The secondary air system works during a cold start to help the cat converter reach operating temperature faster thus burning cleaner. You probably won't feel a ifference in how the car drives however you should address these codes. It may be a faulty air pump, solenoid or valve but I have seen a few of these vehicles with clogged air passeges in the cylinder head. BMW made a tool to check this becuase that would be an expensive guess. The repair involves disassembling the cylinder heads so this is something I would not recommend you try yourself unless you have experience with engine work. You are better off going and having the pressure checked to see if the ports are in fact clogged.

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Richard -- ASE Certified Technician -- 100% Positive Feedback on 41 BMW Accepts
BMW Tech ASE Certified Technician
Reply
July 13 2008 at 5:56 PM (10 minutes and 1 second later)
         
Thanks Richard,
The car has only 70 K miles on it and I doubt the air passages would be clogged that bad already. How would BMW go about isolating the air pump or the other things? Does not the code narrow down these areas? The car has a K+N air filter and I replaced the plugs with Iridiums less than 5 K ago. It runs very strong. I think the light only comes on when I start the car cold in the morning around 65 degrees OAT. Can the car be driven a long distance with no engine damage? I live in the hills of Murhpy North Carolina where there are no qualified BMW techs.
Customer (name blocked for privacy)
Answer
July 13 2008 at 6:03 PM (7 minutes and 2 seconds later)
         
ACCEPTEDCheck Mark

Hello again

That makes sense since the secondary air will only come on for a short period of time during a cold start. Believe it or not I have seen the ports clogg with less than 50,000 miles on the engine. The codes are for low flow so if the pump is not coming on or lost the capability to flow enough air or the vacuum solenoids are stuck that would cause a low flow of air in the system. This would be difficult to diagnose without the BMW scan tool. You should be able to do your drive without a problem but if the problem is not taken care of you may do some damage to the cat conveters.

Hopefully this answers your question and you accept. Positive feedback is appreciated and please let me know if I can assist you with anything else.



Hopefully this answers your question and you hit accept. Positive feedback and bonuses are appreciated and please let me know if I can assist you with anything else.
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Richard -- ASE Certified Technician -- 100% Positive Feedback on 41 BMW Accepts
BMW Tech ASE Certified Technician
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