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Thread: CEL P0155 o2 sensor heater circuit Help!

  1. #1
    Join Date
    Apr 2008
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    South Bend, Indiana
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    1996 Hellrot 328is

    CEL P0155 o2 sensor heater circuit Help!

    So my CEL light came on, and i used an OBD2 scanner and it gave me the code P0155 and it said O2 sensor heater circuit. Does this mean I have a bad O2 sensor? and if so, which one?
    Thanks,
    Jim

  2. #2
    Join Date
    Jun 2008
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    Berkeley CA
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    1996 328is
    The full diagnostic code text is: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

    I'm pretty sure Bank 2 is the post catalytic converter pair of sensors, and Sensor 1 is on the manifold/cat from cylinders 1-2-3.

    What I recommend is get under the car and find the O2 sensor connectors. they are under the drivers side and near the panel covering the fuel filter. See if one of them is loose or a cable damaged. Then unmate both of them, see if any need to be cleaned, and remate. Maybe you just have a dirty/corroded connection and this might help. The CEL should go away in a few drive cycles. Or reset it yourself with the Peake tool.

    If the CEL doesn't go away, or comes back in a coupla days, and you haven't changed your O2 sensors in 100,000 miles, then it's time.
    -Jerry

  3. #3
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    Plymouth Meeting, PA
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    97 M3ti
    No, bank 1 is 1-2-3 and bank 2 is 4-5-6. Sensor 1 is before cat and sensor 2 is after cat. Heater circuit faults almost always equal a new sensor. Bank 2 sensor 1 is the one on the manifold for the cylinders closest to the firewall.

    97 M3ti, 03 Jetta 1.8t

  4. #4
    Join Date
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    Quote Originally Posted by autoxerwgn View Post
    No, bank 1 is 1-2-3 and bank 2 is 4-5-6. Sensor 1 is before cat and sensor 2 is after cat.
    Yeah, I guess that's right. I wish my Bentley manual used the same terminology.

  5. #5
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    Alright, cool. Thanks Guys! so would this be the correct replacement http://www.pelicanparts.com/cgi-bin/...ordering%2E%20 ?

  6. #6
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    Prolly

    But I got my NGK 25013's thru this guy: http://forums.bimmerforums.com/forum...d.php?t=924610

  7. #7
    Join Date
    Mar 2012
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    springboro, ohio, usa
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    1997 bmw 328i

    P0155

    Quote Originally Posted by jbudd21 View Post
    So my CEL light came on, and i used an OBD2 scanner and it gave me the code P0155 and it said O2 sensor heater circuit. Does this mean I have a bad O2 sensor? and if so, which one?
    Thanks,
    Jim
    Similar problem:

    While repairing a driveshaft issue, the exhaust bolts were heated with a torch. When the driveshaft was repaired the engine light came on. I checked the code with my OBDII and it revealed two codes. The first code was for the 02 sensor P0132 (I think this is correct) & the P0155 code for O2 sensor heat circuit. The O2 sensor was replaced and both codes cleared. The car was started and the engine light came back on with only the P0155 code. I replaced the O2 heater circuit relay (which appeared on the connecting spades to be burnt). I cleared this code once again but the same code P0155 keeps returning. Any help?

  8. #8
    Join Date
    Aug 2011
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    Silver Spring, MD
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    128i, M3, 325i
    Quote Originally Posted by autoxerwgn View Post
    No, bank 1 is 1-2-3 and bank 2 is 4-5-6. Sensor 1 is before cat and sensor 2 is after cat. Heater circuit faults almost always equal a new sensor. Bank 2 sensor 1 is the one on the manifold for the cylinders closest to the firewall.
    Actually, this is quite wrong. Bank 1 has Sensor 1 and 2. Bank 2 has Sensor 1 and 2. Grab a code reader one day and run a diagnostic on O2 sensors in your car. You will see TWO Bank 1 sensors and TWO Bank 2 sensors. Show me on an official BMW diagram to support your case, and I will be quiet.

    Anyways, I am having the same problem. I installed brand new sensors in Bank 2 Sensor 1 and Sensor 2 and the light keeps coming back up. I have no idea why.
    Harry // 1995 Avus Blue M3 - 2003 Titansilber 530i M-Sport - 2010 Black Sapphire Metallic 128i M-Sport // BMW CCA #453346 - North Capitol Chapter
    My previous work:
    My 325is M-Tech Restoration Thread
    My 98 M3 and 03 530i Restoration Thread

  9. #9
    Join Date
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    Harry, you restated the contents of the quoted post, just a little differently. The heater circuits have relays. The code is for the heater CIRCUIT.

  10. #10
    Join Date
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    Quote Originally Posted by HarryN View Post
    Actually, this is quite wrong. Bank 1 has Sensor 1 and 2. Bank 2 has Sensor 1 and 2. Grab a code reader one day and run a diagnostic on O2 sensors in your car. You will see TWO Bank 1 sensors and TWO Bank 2 sensors. Show me on an official BMW diagram to support your case, and I will be quiet.

    Anyways, I am having the same problem. I installed brand new sensors in Bank 2 Sensor 1 and Sensor 2 and the light keeps coming back up. I have no idea why.


    He is exactly right. Bank1 is the bank that contains the #1 cylinder, and Sensor1 is before the CAT. Bank1 has Sensor1, before the CAT, and Sensor2, after the CAT. If the sensor heaters have failed, odds are that the sensor is the problem, although there is a relay contact that could be the trouble. The heaters are on only when the Secondary Air Pump is on.

    You replied to a post that is 4 years old, by the way.

  11. #11
    Join Date
    Jul 2010
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    KC, Mo
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    Well, that is what the search function is for !!!

    You brought up the heaters and SAP. My SAP operates properly, yet I get random heater codes AND SAP codes for each bank.

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