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Title: Rear 02 "resistance too high" Post by: gruppe5 on March 21, 2012, 05:57:10 AM Its a 2001 S4, it has new APR downpipes with cats and new front and rear 02 sensors. I keep getting DTC 17522 and 17548 ( not sure on the second code ) for the rear 02 sensors have too high resistance. Inspected all connectors and grounds, last thing I need to meter is the harness from the ECU to the 02 sensor plugs. I can watch temp come up and voltage fluctuate once temp hits 360*C, voltage is around 0.435 and resistance is sky high at 25.5k ohms. If I don't find a problem with the wiring between the ECU and the 02 plugs then I suspect the ECU itself may be the problem, or I got a bad pair of 02 sensors ( unlikely but possible ) the 02's are OEM . Resistance and voltage on the front sensors is normal, and I have a A4 30V V6 at my disposal for comparisons. There is no tune in this car, and aside from the downpipes everything is stock. The downpipes were installed because the originals were broken at the flex. Also the 02 harness' are tied up out of harms way. I am having trouble with this and could use some insight. Keep in mind this is NOT a heater circuit code and no other codes are present.
Title: Re: Rear 02 "resistance too high" Post by: pamvw on March 21, 2012, 09:33:06 AM Hello guys.. I have the same error than him.. ecu 8D0907557P ..can we edit the map and disabled the rear o2 sensor?
What we can do? what is the best option here? what tools we need? Appreciate your advices :'( Title: Re: Rear 02 "resistance too high" Post by: masterj on March 27, 2012, 10:51:25 AM to disable this dtc you have to zero out CLAHSH and CLAHSHE maps ;)
Title: Re: Rear 02 "resistance too high" Post by: nyet on March 27, 2012, 11:42:28 AM Still sounds like bad wiring and/or rear O2 sensors... hopefully its not your ecu.
have you logged rear O2 resistance? you could always just code it all out (but i'd rather find the underlying hardware problem, esp if its the ECU itself) Title: Re: Rear 02 "resistance too high" Post by: gruppe5 on March 27, 2012, 04:19:50 PM Still sounds like bad wiring and/or rear O2 sensors... hopefully its not your ecu. have you logged rear O2 resistance? you could always just code it all out (but i'd rather find the underlying hardware problem, esp if its the ECU itself) Sorry guys, rather new to the coding side of things, I don't have the slightest idea of where to start with that stuff, I have been reading up on it and would like to know what I need. Back to the code(s), I will test the wiring tomorrow I think that the sensors use a shielded cable specifically. I am leaning towards the ECU being the problem, I should know soon. Any other ideas?? Title: Re: Rear 02 "resistance too high" Post by: gruppe5 on March 28, 2012, 04:36:19 PM I also just noticed that when I am logging with VAG-com the ECU shows up as being an " 551 M " box, but the ECU itself has an " H " label on it. Is this normal, I thought that I have heard the "M" box can be re-coded to suit other ECU/cars but I have no idea if that is true. Any help at this point would be appreciated. I did inspect the wiring from the ECU to the sensor plugs, all is well on that front. I also opened the ECU and inspected it for any signs of damage, none found. I am really leaning towards the ECU but if anyone can walk me through deleting the codes that would be great, I downloaded the NEFMOTO software and have a cable but from there I am a bit lost, still reading over on the WIKI.
Title: Re: Rear 02 "resistance too high" Post by: gruppe5 on April 06, 2012, 06:50:10 AM I found that the ECU was/is the problem, monitoring the rear 02 sensor resistance with the original ECU it was shown to go straight to 25.5k ohm after the catalytic converter came up to temp. I replaced the ECU, brought it up to temp and now it is shown as being within spec, 0.10k ohm. :) This has been a thorn in my side for a few weeks and I am glad that a resolution has been found.
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