2c40 code (solved!)

ssphil · 04-05-2016, 03:20 PM

Hello everyone,

I have been troubleshooting the 2c40 error code (2C40 = DME, Internal Error: Lambda Probe (Bank 2) Analysing Chip) for the past week and finally found the problem. I searched on every thread on the internet to find some solutions but to no avail.

I was misfiring a lot and i would have no boost as a result of this code.

The first thing I tried was to change the o2 sensor, no result. I did notice, however, that I inadvertently swapped the 2 upstream sensors during my downpipes install so I put them back to their original location and the misfiring stopped. One problem solved, but still no boost and this 2c40 code.

I then proceeded to check the resistances in the DME since I saw that this was the issue for some people. Everything was good inside so I ruled that out.

Then finally, I inspected the engine harness because if the problem is not at either end of the system, it must then be in the middle somewhere. And sure enough, the harness which goes to the bank 2 upstream lambda probe was pinched under a bolt for the oil filter housing (stupid me!) and the signal wire was grounded to the engine. Repaired the wire and put everything back together and voila, no more 2c40 code!

But still no boost. This was driving me crazy. I was getting the 30ff code so I thought, must be a vacuum line from my inlets install. It was. The vacuum line that goes to the front wastegate actuator was disconnected. Put everything back together and boost was back.

Moral of the story: I better get a damn LED bar for the next time I work on the car!

I hope this can help someone else in the future as I am pretty sure ths would have helped me a lot.

Tonethejackal · 07-02-2021, 10:36 PM

This post was a life saver. I had the code and just found I crushed the sensor wire under the intake manifold after an OFHG change out. My car was also stalling, I guess because the manifold wasn't sealing. Thx!!!

drurqui · 10-29-2022, 07:11 PM

I was changing the valve cover gasket again becouse of a leak and the two upstream o2 sensors. I was reading 2c40 code too. When tried to take out the bank 2 sensor I discovered that it was crushed between the valve cover gasket and the cilinder header and making a short circuit. When I finished clear the codes, start the car and no 2c40 again.

Thanks for your help

04-05-2016, 03:20 PM	#1
ssphil Private 12 Rep 54 Posts Drives: E90 335i & F10 550i Join Date: Jul 2015 Location: Quebec, Canada iTrader: (0) Garage List 2007 BMW 335i [10.00] 1995 BMW 530i [10.00]	2c40 code (solved!) Hello everyone, I have been troubleshooting the 2c40 error code (2C40 = DME, Internal Error: Lambda Probe (Bank 2) Analysing Chip) for the past week and finally found the problem. I searched on every thread on the internet to find some solutions but to no avail. I was misfiring a lot and i would have no boost as a result of this code. The first thing I tried was to change the o2 sensor, no result. I did notice, however, that I inadvertently swapped the 2 upstream sensors during my downpipes install so I put them back to their original location and the misfiring stopped. One problem solved, but still no boost and this 2c40 code. I then proceeded to check the resistances in the DME since I saw that this was the issue for some people. Everything was good inside so I ruled that out. Then finally, I inspected the engine harness because if the problem is not at either end of the system, it must then be in the middle somewhere. And sure enough, the harness which goes to the bank 2 upstream lambda probe was pinched under a bolt for the oil filter housing (stupid me!) and the signal wire was grounded to the engine. Repaired the wire and put everything back together and voila, no more 2c40 code! But still no boost. This was driving me crazy. I was getting the 30ff code so I thought, must be a vacuum line from my inlets install. It was. The vacuum line that goes to the front wastegate actuator was disconnected. Put everything back together and boost was back. Moral of the story: I better get a damn LED bar for the next time I work on the car! I hope this can help someone else in the future as I am pretty sure ths would have helped me a lot. __________________ Weekend Warrior: '07 E90 335i, JB, 6MT, DR 6266, Fuel-it stg3 lpfp, Helix, Prometh WMI, 7.5" ARM FMIC, JB4+MHD, Built engine Daily Driver: ‘16 F10 550i, SG, 8AT, JB4, ARM downpipes, XHP stg 3 trans tune Retired: '18 F30 340i '95 E34 530i, '99 E46 323i, '00 E46 323i Last edited by ssphil; 04-05-2016 at 03:21 PM.. Reason: Forgot to write some words
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07-02-2021, 10:36 PM	#2
Tonethejackal Enlisted Member 9 Rep 46 Posts Drives: 2008 335i Join Date: Aug 2015 Location: Lavon, TX iTrader: (0)	This post was a life saver. I had the code and just found I crushed the sensor wire under the intake manifold after an OFHG change out. My car was also stalling, I guess because the manifold wasn't sealing. Thx!!!
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10-29-2022, 07:11 PM	#3
drurqui Registered 0 Rep 2 Posts Drives: 2007 328i Join Date: Sep 2017 Location: San Salvador, El Salvador iTrader: (0)	I was changing the valve cover gasket again becouse of a leak and the two upstream o2 sensors. I was reading 2c40 code too. When tried to take out the bank 2 sensor I discovered that it was crushed between the valve cover gasket and the cilinder header and making a short circuit. When I finished clear the codes, start the car and no 2c40 again. Thanks for your help
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