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  #11  
Old 09-14-2019, 08:43 PM
ard ard is offline
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Quote:
Originally Posted by pshovest View Post
O2 sensors usually don't fail in pairs,



Agree, for sure. When you see mutiple codes pop up in a single moment, that can be a clue as to what causes that unique pattern....






Unless one failed at 100k, one at 120k and one at 150k. for example. For all we know the CEL has been on for years, only once it starts driving like crap does this become urgent. Hypothetical of course, not speaking to OPs facts







The heater circuit error cannot be explained by injectors...maf...fuel...pressure sensors..blah blah blah. Only one thing causes that code: an open circuit (ie no current) in the circuit that connects to the O2 sensor preheater. The list is short: O2 sensor, wire(s), connector, fuse. (Or...the DME is faulty, just to be accurate.)



You ask 'any work done?'... indeed, someone messing with cats and O2s, might do that.


Has anyone asked:



"How long has the CEL been on?"


"Did ALL these codes appear at the same time, just all at once and recently?


"If not, how did these CELs evolve over time?
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  #12  
Old 09-16-2019, 01:03 PM
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Not sure what to make of the heater code, since only 1 of the 2 pre-cat sensor shows the code. Running well w/o MAF rules out valvetronic, eccentric shaft sensor, ignition or fuel pressure problem. Lean mixtures from bad MAF or vacuum leaks still fit the symptoms. O2 sensors don't come into play until engine has run for 60-90 seconds and sensors have been heated to operating temp....engine should run ok until O2's get hot. Still doesn't sound like an O2 sensor problem to me. Multiple problems are possible.
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  #13  
Old 09-16-2019, 05:29 PM
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Viktimize is an unknown quantity at this point
Troubleshooting is always good to help narrow a problem and avoid spending unnecessary money on parts. But this N52 is not rocket surgery. It's been around for over a decade. And they are very well known for neding certain things every 60-100k Miles. VCG, Plugs, Coils, and all vaccum hoses and rubber in the intake system replaced. Every one I've ever worked on has been the same, if I try to replace individual parts based on troubleshooting, I end up chasing my tail and having problem after problem. So I replace this stuff in batches now.

Another issue that causes rough starts(will also cause hesitation from a dead stop)is the DISA valve. Easy enough to pull it out of the manifold and check it. If it's not closed when you pull it out, it's no good. Another potential problem you might have on top of what seems like a bad vaccum leak and potential O2 sensor.
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  #14  
Old 09-17-2019, 01:39 AM
ard ard is offline
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Viktim- what I was getting at..... 'rifle shot diagnoses' in a car that has a a ton of deferred maintenance can be a cluster





Quote:
Originally Posted by pshovest View Post
Not sure what to make of the heater code, since only 1 of the 2 pre-cat sensor shows the code. Running well w/o MAF rules out valvetronic, eccentric shaft sensor, ignition or fuel pressure problem. Lean mixtures from bad MAF or vacuum leaks still fit the symptoms. O2 sensors don't come into play until engine has run for 60-90 seconds and sensors have been heated to operating temp....engine should run ok until O2's get hot. Still doesn't sound like an O2 sensor problem to me. Multiple problems are possible.



When the SAP comes on during a cold start, the DME powers the heater circuits in each o2 sensor. If it fails to see current it IMMEDIATELY sets a 'heater circuit code' (All o2s are on the same fuse, so a fault on one sensor points away from a fuse and towards a sensor or wiring issue.)



Here's the thing.... UNLIKE other O2 sensor codes, that must 'wait' unitl the DME is in clsed loop before they are evaluated by the DME, the heater circuit is ONLY tested initially and on a cold start.


(I had a car that had hit some debris that took out the O2 connector, and only the heater pin. Ran fine. Started fine when warm- immediate code when cold)


Here is something I seem to recall, but cant find: If the DME sets a heater code, does this prevent the DME from using that O2? Perhaps not letting it enter closed loop? I dunno, cant find it right now.




Wonder if the OP will tell us if the MAF he ordered fixes this.....
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