CEL P0155 o2 sensor heater circuit Help!

[jbudd21]

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

[berkeleyEE]

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

[autoxerwgn]

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.

[berkeleyEE]

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.

[jbudd21]

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

[berkeleyEE]

Prolly

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

[hozem396]

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?

[HarryN]

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.

[snaponbob]

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.

[JDStrickland]

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.

[snaponbob]

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.

[alantrundle]

Hi,

I’m also seeing a persistent P0155 error, which indicates that there is a problem with the heater circuit on sensor 1 (pre cat) bank 2 which is cylinders 4, 5 and 6.

I have checked that resistance across both Pre cat sensors (white and purple wires) and seeing about 11.5R on both bank 1 and 2.
I have also checked the voltage to the heater circuits and seeing 12.9V at both banks, so no problems there.

I did notice that pre cat sensor (1) connector on bank 2 was loose, ie it wasn’t clipped in properly, so it may have been loose.
WD40 and I’ll keep an eye on it.

Some of the heat proof materials on my sensor cables are showing slight signs of ware and tare/ heat damage, but can’t any evidence that these is a short circuit.

I will keep you posted.

Using a genetic Bluetooth 4.0 ELM adapter, and Car Scanner Pro on an iPhone 8 Plus for diagnostics.
Absolutely fantastic !

I have also deleted my POST CAT sensors on my ECU, and as such are not connected.
(Just to rule out)

Thanks

[snaponbob]

This was 6 years ago !!! Problem was solved and the car has been replaced.