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Hi Everyone,

I am new to this forum, however, I hear its awesome. Anyways, my wife's 325i starting to go into limp mode after reaching 45 mph or 4k rpms. The EML light, traction control light and brake light would come on and the car would go into limp mode. As soon as she pulled over and turned the car off and then back on, the problem would go away. I hooked up my Foxwell scanner to the car and received a P16A7 error code.

Here is what I've done to attempt to fix the problem. I changed the crankshaft sensor, both cam sensors (intake and exhaust), cleaned the throttle body and examined the disa valve. I also changed out the intake boots. Proud of myself, I took my wife for a ride after I put the car back together and 10 minutes later - BAM - it went back into limp mode. Buzz kill to say the least.

The first person who can tell me what's wrong and I successfully fix the problem, I will treat you to a nice steak dinner!!! I am absolutely at my wits end on this one and my wife wants her car back. Let me know if anyone has had this issue and were able to fix it. Thanks Everyone.
 

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We talking Ruth***8217;s Chris or Sizzler here? :rofl:

P16A7 BMW: Engine Control Module Self-Test Mass Air Flow Sensor Monitoring Fault
Check for plugged cats with an exhaust backpressure test.
Look for an under reporting MAF sensor by checking the MAF value at warm idle, should be 3.6-4.2 g/s.
 

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As a definitive test, as I did, remove the pre cat o2 sensors and go for a drive. If she doesn't go into limp mode then you have your definitive answer.

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We talking Ruth’s Chris or Sizzler here? :rofl:



Check for plugged cats with an exhaust backpressure test.

Look for an under reporting MAF sensor by checking the MAF value at warm idle, should be 3.6-4.2 g/s.
Balidawg will be joining for steak. He was a major major major helping hand in my limp mode issue last year.

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Discussion Starter #8
EML and Traction Control Light

I can 100% tell you the problem. One of your cats is clogged. Same exact symptoms I had this same exact time last year. See my thread...

https://forum.e46fanatics.com/showthread.php?t=1242285&goto=newpost

I live in PA, where should we go to dinner? lol

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I will definitely see if that's the problem. I did read something about that before. Either way, if it is the issue, I will be sending you a gift card buddy. I see you are from PA. I'm from Bensalem outside of Philly. Go Birds and thanks....
 

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Discussion Starter #9
EML and Traction Control Light

We talking Ruth's Chris or Sizzler here? :rofl:

P16A7 BMW: Engine Control Module Self-Test Mass Air Flow Sensor Monitoring Fault
Check for plugged cats with an exhaust backpressure test.
Look for an under reporting MAF sensor by checking the MAF value at warm idle, should be 3.6-4.2 g/s.
I will check the MAF sensor also. My first check will definitely be the cats. Thanks.
 

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I will definitely see if that's the problem. I did read something about that before. Either way, if it is the issue, I will be sending you a gift card buddy. I see you are from PA. I'm from Bensalem outside of Philly. Go Birds and thanks....
Awesome! Can't advocate the bird's lol, I'm a Bill's fan (poor me) lol.

And if it is is the cats, I recommend not going aftermarket. I've been told by a few old timers that there are significantly fitment issues. I found a set of used genuine BMW cats on eBay with 82k miles.

Also another quick test to do as well to see if it's the cats is to unplug the maf and go for a drive. If she doesn't shut off, it's a pretty good indicator that it's the cat(s).

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Also another quick test to do as well to see if it's the cats is to unplug the maf and go for a drive. If she doesn't shut off, it's a pretty good indicator that it's the cat(s).
Well it could still be the MAF in that scenario. If it is the cats (and there's 99.99% chance it is), then you can really cause the back pressure to skyrocket and probably risk burning out the valves. Mine pretty quickly got to the point where it couldn't physically rev over 4k.
 

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Yeah that works as a diagnostic procedure. Though you can really cause the back pressure to skyrocket and probably risk burning out the valves. Mine pretty quickly got to the point where it couldn't physically rev over 4k.
Mine must have just been clogged at the threshold of good vs bad. I drove around from Nov to Feb of this year are until I figured out it was the cats.

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Discussion Starter #13
Well I just returned from performing the O2 sensor removal and ran it for 5 miles. The same eml, traction control and brake lights came back on and the car went into limp mode. Only twice this time which was a lot better than previous test drives. What do you think? I have not tried the MAF sensor test yet. I am at a complete lost. Really hoping it was the cats....
 

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Best is to measure back pressure. Could be that removing the O2 sensor relieved back pressure enough to improve your symptoms, but not enough to eliminate it. I'm still pretty confident it's the cats.
 

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Discussion Starter #15
Is there a way to clean the cats or does this call from a total replacement of them? What about the vanos? Could that be the problem. I only have three things left to check: cats, vanos or computer.
 

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I think BaliDawg is right. I just went through your exact symptoms and even replaced a pair of MAF's eventually I believe it was the MAF terminals being loose? I manhandled the connectors to the point that strong force was required to reconnect!

I have about two months and 2K trouble free miles, just saying.
 

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I concur with the others, clogged cat/s. My bank 2 cat was clogged and got the same symptoms, plus misfires and lean codes. Grab a gauge and check the back pressure at different RPMs, quick and easy test.
 

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Well I just returned from performing the O2 sensor removal and ran it for 5 miles. The same eml, traction control and brake lights came back on and the car went into limp mode. Only twice this time which was a lot better than previous test drives. What do you think? I have not tried the MAF sensor test yet. I am at a complete lost. Really hoping it was the cats....
I believe your cats are super clogged then or at least one is. Unplug the maf and go for a jaunt. See if the problem occurs. I have a good maf here I can lend for testing purposes. If you pay shipping I'll send it out to you.

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Discussion Starter #20
We I checked the pressure on the cats and the pressure was good. Was told they weren't clogged. Now I am wondering if the downstream O2 sensors are bad and that's causing the problems. I didn't realize the down stream O2 sensors were connected so far away from the cats. Order two new sensors today so I will try that out and see what happens. May need to replace the upstream O2 sensors as well. Thoughts???
 
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