Z4 with p0134/p0135

[carlsson01]

Good day,I’ve had this code for sometime now and already did replace the o2 sensor,but the codes came back. One mechanic told me it might be the engine ecu not reading the o2 sensors so it has to be replaced and one said the wiring harness needs to be checked. If it is indeed the ecu,can I just get one on ebay and plug it in? Is it that easy or some programming needs to be done? Thanks in advance.

[psycleridr]

You're positive its not the sensor again? What kind of sensor did you replace it with?

[tekoo]

You’d have to check the wiring connection (sockets) of the oxygen sensors to see if they are properly seated in the respective sockets and powered up and getting signal from the DME. You may also want to attempt to clean the sockets with compressed air and electronic board cleaner and replug the sensors in securely. This will help identify if the problem is in the sensors/sockets or upstream.

Here is the wirining diagram:
https://www.newtis.info/tisv2/a/en/e...l-unit/qPVB2Ql

https://www.newtis.info/tisv2/a/en/e...ontrol/qBuKAmT

B62101 & B62201 in the diagrams are the oxygen sensors.

Socket Pinout for B62101
85E65ED3-0AA9-4399-9B5E-B24B74FAEA49.jpeg
Socket pinout for B62201
F4594BA7-99CB-4E90-93A2-621654D42039.jpeg

You will also need to confirm all ground points in this diagram are intact and not loose/broken:
311F8CBB-A4FC-4D67-B896-1009B53841F2.jpg

You should also check fuse 3 & 4 & scan the vehicle for other errors.

In regards to DME (ECU) replacement; you’ll get all the answers from the following thread:
https://www.bimmerforums.com/forum/s...-Start-Problem

However if the problem is a bad connection, wiring or oxygen sensor (downstream from DME); replacing the DME would be a waste of time and money! You have to figure out where the problem is!

Here are some good links for troubleshooting help:
https://www.google.com/amp/s/repairp...code-p0134.amp

https://www.google.com/amp/s/forum.e...=1084820&amp=1

[tekoo]

More useful explanations and troubleshooting suggestions to help you diagnose in the following link. FYI (PCM=ECU=DME in this case)

https://www.ls2.com/boggs/dtcs/DTC%20P0134.htm

When you understand the oxygen sensor’s circuit and function well you realize that many things can trigger the same error code as it is a circuit of components that operate in multidisciplinary fashion and if one fails, the whole circuit fails and an error is generated. So in your case the are many possibilities:

1- The oxygen sensing system may be 100% functional and intact but detecting abnormally steady combustion gas concentrations from the exhaust system. In this case the exhaust system may have a significant gas leak where the sensors are located leading to poor fluctuations in concentrations of different gases and therefore a falsely decreased sensor sensitivity. You may need to verify the exhaust system is not leaking and that there is an air tight connection where the sensors are seated (check the threads).
9E319AF4-2769-4337-AB52-ED842630FDE2.jpeg

2- Oxygen sensors are good but not connected properly (defective or heavily soiled sockets) or defective wiring from the sensors to the DME (cut wire or loss of insulation creating short) or defective grounding points that are loose/corroded (check image in prior post for location). Less likely DME software may need reflash or rarely DME may be defective and needs replacement (very unusual to be first step in troubleshooting algorithm).

3- Oxygen sensors are defective, bad quality or non compatible (some people suggest the sensors must be Bosch to avoid errors). All sensors have to be replaced at same time to avoid repeat codes from interval sensor failure.

If you decide to perform the troubleshooting yourself it might be more useful to use BMW specific diagnostic software (e.g INPA or ISTA) as it provides more details about the specific codes as well as live data streaming and voltage readings during vehicle’s operation and sometimes even step by step guide to acquiring more details. More info about INPA and ISTA can be found in the software section of this forum.

[carlsson01]

Good info..will read them and see what I can pick up.. thanks.