[northpaw]

Hello All,

I recently had a no start issue with my E90 06' 325i. I went out and got a starter and was just praying that would solve my issue. Went to replace it and the DMF grease had exploded into my bell housing and covered every inch of it. Theres my issue.

So I replaced the DMF with a SMF and a Stage 2+ clutch, installed all new coilovers at the same time, and replaced the starter anyway cause I had one and the intake already out. Eventually I get everything buttoned up and the car starts and runs great. Engine sounds wonderful, seemingly no issues. Then the CEL comes on. Oh yay, one problem after another.

At the time, I didnt give a crap. I was done working on the car and wanted to enjoy the upgrades, so I did. I quickly pull codes and its a P0052. quick google search and Pelican says its a faulty O2, so I said, Nah, Im driving instead and I did for about a month. Car drives great, got the new clutch broken in, and everything is seemingly fine.

Month Later:
Whip out the code reader again, and its throwing a P0052 still (HO2S Heater Circuit High Voltage Bank 2 Sensor 1.) So not thinking about the definition to hard, I buy a replacement O2 and a week later, its installed. Codes still there, I cleared the code, it came back, tried pulling power from the battery, code came back.

I went and looked back at the definition and realized its an Electrical fault for the Sensors heater. I am not by any means educated on electrical and so here I am. Looking for help. Im trying to keep this a do at home job and I found some forum threads that seemed related and educational on the heater circuit. I plan to link them below and quote 2 specific posts for reference.

What should I do?

thread: https://www.e90post.com/forums/showt...ighlight=p0052


Post 1:

Originally Posted by gbalthrop

TWO OBSERVATIONS:
1) Avoid shops that believe that a fault code means replace "Part X" and do NO examination/testing of the associated electrical system.
2) Request money back from shop that repeated a prior R&R and achieved the same result: "Insanity."

Here is the TIS circuit diagram for the Lambda (O2) Sensors. Note the Orange wire from fuse F38 that supplies power to ALL O2 Sensor Heaters, including the Pre-cat Bank 2 sensor, B62201. Its "Installation Location" follows:
https://www.newtis.info/tisv2/a/en/e...ontrol/vF5QqMj
https://www.newtis.info/tisv2/a/en/e92-335i-cou/SHRnn4K

Note the "87" above the 30A Fuse Symbol for F38. That means that the fuse is powered only when Terminal 87 is active. When ignition is on, any Terminal 87 fuse should be powered. I would begin by locating BOTH Pre-cat O2 Sensor connectors, X62201 & X62101, and testing for 12V+ at the Orange wire, Pin #4, of each connector, particularly X62201 for Bank 2. Here are the Installation Location and Connector View for those connectors:
https://www.newtis.info/tisv2/a/en/e92-335i-cou/SCO2U5k
https://www.newtis.info/tisv2/a/en/e...i-cou/CT6giy7l

Also inspect the connector X62201, the sockets, pins & associated wiring, for any sign of damage, and clean the pins & sockets with electronic contact cleaner. Pin #3, White/Blue wire, at X62201 is JUST as important as Pin #4, in that it supplies the GROUND from the DME to activate the Heater.

Please let us know what you find,
George

Post 2:

Originally Posted by gbalthrop

I realize we may have a bit of a language barrier here. You certainly understand my ONLY language better than I understand YOUR Native language.

There are two different issues to be dealt with here as I see it:

1) What is the proper DEFINITION of the three different codes you have listed? Related question: WHAT Scan Tool or software do you have available to read codes and their Definitions?
2) How exactly did you perform the tests for which you describe results? I can't understand why Pin #3 (White/Blue wire) voltage should be 4.33V rather than ~ 0V (in reference to Chassis Ground) or why BOTH Connectors should have the same voltage, when only ONE Sensor is setting Fault Codes.

I. Fault Codes & Definitions, Bentley listed FIRST, then BMW Fault Code Lookup:

A. 2CA7 (3 Different Definitions & P-codes):
P0059 | 2CA7 | H02S Heater Resistance (Bank 2 Sensor 1)
P0155 | 2CA7 | 02 Sensor Heater Circuit (Bank 2 Sensor 1)
P166F | 2CA7 | Internal Control Module Measurement Error 02 Sensor Heating (Bank 2 Sensor 1)

N54 P0155 2CA7 DME: Oxygen sensor heater 2 before catalytic converter: Function MSD80

B. 2CAB:
P166F | 2CAB | Internal Control Module Measurement Error 02 Sensor Heating (Bank 2 Sensor 1); NOTE: SAME Def as for 2CA7 above (3rd Def)

N54 | P166F | 2CAB | DME: Oxygen sensor 2 before catalytic converter: Temperature | MSD80

C. 2C9D:
P0050 | 2C9D | H02S Heater Control Circuit (Bank 2 Sensor 1)
P0051 | 2C9D | H02S Heater Control Circuit Low (Bank 2 Sensor 1)
P0052 | 2C9D | H02S Heater Control Circuit High (Bank 2 Sensor 1)

N54 | P0050 | 2C9D | DME: Oxygen sensor heater 2 before catalytic converter: Activation | MSD80 (ALSO P0051 & P0052, SAME Def.)

Regardless of which Definitions are applicable it appears that the Pre-cat O2 Sensor on Bank 2 (B62201 in Schematic) is NOT heating properly. That could be due to (1) an open circuit or intermittent 12V+ power supply from F38 via the Orange wire at Pin #4 of Connector X62201, (2) NO/Intermittent Ground supplied by the DME via the White/Blue wire at Pin #3 of X62201, or (3) a burned out or open resistor circuit in the Sensor (MOST UNLIKELY given that 3 different sensors have given same faults).

Unfortunately, there have been several reports of MSD80 failure resulting in lack of ground supplied to ONE of the two Pre-cat O2 Sensors. That is an internal DME fault and NOT a wiring or connector issue, so if you are NOT getting ground signal at Pin #3 (White/Blue wire) of Connector X62201, I would suggest doing BOTH of the following:
1) Test the other Pre-cat O2 Sensor Connector, X62101, for similar voltage at Pin #3 with ignition On.
2) Test at DME Connector X60002, Pins #12 & #13 for voltage in reference to chassis ground (with ignition ON).

If you are getting O2 Sensor Heater Fault codes ONLY for Bank 2 (NOT Bank 1 as well), then there MUST be a difference between pins in at least ONE of those tests above. If NOT, then either I don't understand something correctly, or my description of how to conduct the tests was NOT clear to you.

If you have either of the two (original & Bosch replacement #1 ;-) O2 sensors that shop & Dealer replaced, you can simply plug that into the connector and see if the heater works. Of course you can "bench-test" the O2 Sensor heater by applying 12V+ & Ground respectively to Pins #4 & #3. Assuming it heats when bench-tested but doesn't heat when connected to X62201, do the following tests at Connector X62201. Measure Voltage at Pin #4 (Orange wire), which should be 12V+ (with reference to Chassis Ground) with ignition on. Then measure voltage between Pin #3 (White/Blue wire) and Chassis Ground, also with ignition ON. That voltage should be ~ 0, as that needs to be a ground to have current flow through the heater element. I'm NOT sure of the BEST WAY to test a Control Module-supplied Ground, as you do NOT want to damage the DME by shorting the wrong thing to ground. Simply measuring voltage in reference to ground does NOT rule out an open circuit, so you might want to do a second test, measuring resistance, for "continuity to ground."

Here's the TIS circuit diagram for O2 Sensors again, showing the Connectors you tested, X62201 & X62101:
https://www.newtis.info/tisv2/a/en/e...ontrol/vF5QqMj

Please let me know if ANYTHING in the above is NOT clear/correct, conduct the voltage measurements again, testing as described above, and let us know the results.

George

[northpaw]

Bump, Anyone never run into this before?

[northpaw]

Bump, still need some help.

UPDATE: Issue is ongoing but its still the only code since I posted and hasnt devolved into something worse. I am about to just buy a whole new cat for bank 2. Hoping some input will be gained here.