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Discussion Starter · #1 ·
So. My first problem. Got the alarm yesterday while driving. Checked with a C110 obd scanner. Found it was alarm 0171 (system to lean) . Went over i take and so to seff if I could find anything loose. All good.
I bought the car not long ago. Coil unit changed a year ago.

This was ofc at the worst possible time as I am supposed to deliver car for 2round at MOT now.

Anyways. I am not able to delete the alarm. If its a air leak. Bad sparkplugs or whatever. Should it not be possible to delete the alarm? (and ofc it will come back if something is bad).

I tried deleting it with the obd scan unit. Says deleted.. But if i recheck its still active. Also tried the disconnect battery reset. Same.

But if I go to the "diagnosis" on the mini dash. And check 14.0-14.4 there is no alarm. But still engine Check light is on.

Could need a pointer her.

Thanks
 

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if the code wont reset then likely sensor faulty, or wiring harness faulty, or ecu faulty, start with sensor and work backwards
 

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Discussion Starter · #3 · (Edited)
if the code wont reset then likely sensor faulty, or wiring harness faulty, or ecu faulty, start with sensor and work backwards
Thanks. Then we talk the O2 sensor yes? I can fiddle some with the obd 2 scanner. Maybe it can read the O2 value.
I went over wire connections when checking for air leaks. Had the plastic "wall" off before 2nd MOT, changed all brake lines. Will check once more, maybe something not plugged in perfectly. Drove about 15km after this before I got the engine light on.
*edit
When looking on the alarm list, if it is something with the O2 sensor, should I not have some o2 alarm also? Something from P0130-P0167? Or is that not necessary true?
 

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or its a air leak somewhere and sensor is picking it up , need live data diagnostics and also need a scan tool that gives all the codes as most cheap scan tools dont see all P-codes ie dealer only as such,
 

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Discussion Starter · #5 ·
or its a air leak somewhere and sensor is picking it up , need live data diagnostics and also need a scan tool that gives all the codes as most cheap scan tools dont see all P-codes ie dealer only as such,
Okey. So I used the obd2 scanner. And when running the engine. The upstream o2 sensor varies from 0.01V to 0.40v. Usually 0.2V or lower. But going very rapid up and down.
The downstream one being pretty steady at 0.92-0.95V. This is at idle after motor is warm. Also noticed that both o2 sensor get a peak of voltage at around 9.5-10V.might be a bug in the scanner.

Anyways I think this points to a faulty upstream o2 sensor. Do you agree?
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thats fairy normal on 02 sensors the post cat always run slower than upstream sensor, and normal range would be what you have maybe be a tad low on the pre cat sensor would expect to see 0.7v middle voltage, i would be smoke testing the inlet see if have any leaks where should not, even a injector seal can cause mixture issues, the fact the both sensors read differently would tell me the cat is still in there so have a restriction between the sensors,,
 

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Discussion Starter · #7 ·
thats fairy normal on 02 sensors the post cat always run slower than upstream sensor, and normal range would be what you have maybe be a tad low on the pre cat sensor would expect to see 0.7v middle voltage, i would be smoke testing the inlet see if have any leaks where should not, even a injector seal can cause mixture issues, the fact the both sensors read differently would tell me the cat is still in there so have a restriction between the sensors,,
Yes I understand. But the value stay like this. The pre cat has 0.2v or lower middle value. And after cat has 0.9 ish value.
How can it be lean before cat and rich after cat? If not one of the O2 sensors are faulty (if ecu is Reading correct of course).
 

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faulty cat.. ecu fault , 02 sensor fault, broken exhaust flexi, rule of thump 02 sensors and cat should be treated as whole unit and replaced together , on a perfect running engine that using no oil and never had head gasket failure tyipacl life span 80-120,000 miles is a guide from the makers
 

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Sometimes when reseting codes it akes a recycle of 5 key starts to finish. My 03 S needed this, so I drove a couple miles, pulled over, restarted and drove another couple miles, did this 5 times, code never came back. Same with my wife's 2011. Countryman S.
 

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Sometimes when reseting codes it akes a recycle of 5 key starts to finish. My 03 S needed this, so I drove a couple miles, pulled over, restarted and drove another couple miles, did this 5 times, code never came back. Same with my wife's 2011. Countryman S.
some codes they will mainly emissions based codes , wont do it on full faults ie everytime start car it sees a fault there and then and keeps relogging it , plus to be honest just driving on from ever getting a EML up is not advised as could destroy the engine if the fault is not fixed
 

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Discussion Starter · #11 ·
Thanks for help. I have ordered a set of sparkplugs and a new upstream o2 sensor.
Doesnt hurt to have in spare anyways. Will be away for work until next weekend. Will post a update after I have done changes.
 
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