S4 / RS4 (B5 Platform) Discussion Discussion forum for the B5 Audi S4 & RS4 produced from 1998-2002

DTCs: 17521,16684, 16685, 16686, and 16687

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Old Jun 21, 2008 | 07:22 PM
  #1  
GoodMatt's Avatar
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Default DTCs: 17521,16684, 16685, 16686, and 16687

So, I've finally decided to get the stage 3 (AWE)running correctly. It's been 2+ years and I've only put about 1500 miles on it because of various issues. I had the AWE cold start problem and then a random throttle cut issue...

Anyways, it's bee parked for 9 months and I'm ready to do some work.

No check engine light and it runs great most of the time, but will cut throttle at random times.

Codes:

17521 - Bank 1 - Sensor 1: Internal resistance too large (sporadic)

16884 - Random/Multiple Cylinder: Misfire detected

16885 - Cylinder 1 misfire detected

16886 - Cylinder 2 misfire detected

16887 - Cylinder 3 misfire detected

I've had a set of O2 sensors sitting around for 3 years, so I figure I would throw those in. I also have a new set of plugs that will go in at the same time.

Does the same control module fire cyl 1-3 or does one fire 1-3-5 and the other fires 2-4-6?

Any advice is appreciated...

-Matt
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Old Jun 21, 2008 | 07:37 PM
  #2  
Nigel (no more S4)'s Avatar
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Default Throw in the O2 sensors, and change the ICM

There's 2 that fire each bank, 1-2-3 and 4-5-6. Misfires on the same bank usually mean an ICM failure.
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Old Jun 21, 2008 | 07:54 PM
  #3  
papuc (MMI S4)'s Avatar
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Joined: Nov 2007
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Default

Matt your right, the POS closests to the front controls cylinder 4-6. try swapping them
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