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Code 1221

 
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alexgraf



Joined: 17 May 2002
Posts: 319
Location: Michigan, USA

PostPosted: Thu Jan 22, 2009 10:12 pm    Post subject: Code 1221 Reply with quote

Hi:
Code 1221 lit up last night on my '95 325 iS. I have been doing some diagnostic before spending $80 for a new O2 sensor.

I am trying to determine if the O2 heater function is working properly. My question is: does the ECU provides voltage to the heater at startup or is always on. I measured the voltage with the engine warm and there is no voltage.

Thanks for your help.
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mabm325



Joined: 09 Jul 2001
Posts: 572
Location: Montreal, Canada

PostPosted: Fri Jan 23, 2009 9:08 am    Post subject: Reply with quote

I believe the pre-heater is on only for a short period of time. You should check for voltage with a cold engine. It would not hurt to check the heater element resistance as well while you are down there.
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Hers: 1988 325iA/4 (232000 km)
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alexgraf



Joined: 17 May 2002
Posts: 319
Location: Michigan, USA

PostPosted: Fri Jan 23, 2009 1:41 pm    Post subject: Reply with quote

Thanks mabm325. I checked the resistance of the heating element and is about 3ohms, which at 13V, should give about 40Watts (reasonable for such a small device).

I will check the situation with the engine cold and reply.
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alexgraf



Joined: 17 May 2002
Posts: 319
Location: Michigan, USA

PostPosted: Sun Feb 01, 2009 2:29 pm    Post subject: Reply with quote

Hi:
just an update. I installed a new O2 sensor and the ligth went off after three cycles of start, warmup, and stop.

The only thing still not clear is when the sensor heater is activated. I measured the heater voltage from the connector at startup (20 sec after startup and there was no voltage. Any clarificatons will be good addition to the board.

Thanks,
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