can you test oxygen sensors?
 

Hi still having trans fail prog, after a trans rebuild. I have worked out that the front oxygen sensors are on the same circuit as the trans ecu. Can these sensors be tested in any way ie resistance or it it simply replace as trial and error.

thanks.

A good scan tool should be able to monitor the voltage on the O2 senors and put it on a graph. If they are reading perfectly, that will tell you they are good. But if they are not reading properly, that will not necessarily tell you they are bad, as other things can cause them to read improperly, (ie bad cats). Sometimes their physical condition is a dead giveaway once removed, (they can get all loaded up with carbon). But they also can deteriorate with mileage.

Thankyou very much.

Test with Scope
 

If you know anyone or a shop with a scope, such as a Picoscope Automotive Oscilloscope, you can monitor the voltage of the O2 sensors during a WOT blip. Their voltage behavior during such an operation can give an indication of whether or not they're working correctly. Go to PicoScope USB Oscilloscopes - the PC-based oscilloscope from Pico Technology and watch some of the videos they have on their site.

Oxygen sensors would not cause a transfail program.

Thankyou, I saw a post where a guy found the cables going to the front oxygen sensors were chafing of the driveshaft and he said it caused him a 'trans failsafe error'? or maybe I just missread it?

http://www.xoutpost.com/bmw-sav-foru...ghlight=oxygen

Unless you have a blown fuse in the engine compartment, oxygen sensors alone wouldn't cause a trans failsafe program to be activated.

Your best bet is to see exactly what kind of trouble codes are stored in the DME and EGS then check all related fuses, that is where I would start and not by spending money on oxygen sensors.

Of course if you find wires that are shorting out or frayed never a bad idea to address those issues.

It sounds like you might need to find someone that can do some proper troubleshooting. Maybe a better indie?

Hi, thanks for that, just grasping at straws now, dealer told me it was gearbox internal fault, they told me the same after I had a rebuild, so a bit stuck at the moment, having a used trans ecu fitted this week.