Major DME Issue to separate the men from the boys. Let's see what you know...

[Paul in NZ]

could it be a short in the o2 sensor wiring??

[Gearhead]

could it be a short in the o2 sensor wiring??

Thanks Paul!

The wiring was already ohmed out with no shorts or open circiuts anywhere. That and when the scanner is attached, we're getting good 02 values without any strange spikes or open/zero values.

Data Stream
02 Sensor 1 Integrator - 1.00193
02 Sensor 2 Integrator - 1.00000

02 Sensor 1 reading = 0.49 v
02 Sensor 2 reading = 0.54 v

Plus, these values change readily when enrichening (starting fluid) or leaning out (intentional vacuum leak) the a/f mixture. Even if there was an open or short in the 02 wiring, would that account for the DME not having any mixture adaptation values?

[Paul in NZ]

if the O2 circuit ws not functioning properly then there would not be any means to adapt the mixture?

[Gearhead]

if the O2 circuit ws not functioning properly then there would not be any means to adapt the mixture?

Correct, if the circuit was open, then there would be no values for the DME to use as a basis for the Mixture Adaptation. However, we were sitting there with the scanner attached looking at the 02 sensor values on one data stream (meaning the circuit is good) and watching the voltage sweep up and down as we enriched and leaned-out the a/f mix manually... yet at the same time, the mixture adaptation was reading 0.00 on both banks. So WE could see the 02 values, but the adaptations were not responding to this available data.

Now, this very thing happened with two different DMEs. Granted, neither one was new, but both passed all bench tests according to my DME tech and the 2nd one is the unit he used in his shop as the "known good" unit when troubleshooting.

[MBXB]

- Checks all wiring for faults. None. All checks out well.

Did you check the cold air sensor, and water temp sensors?

[Gearhead]

- Checks all wiring for faults. None. All checks out well.

Did you check the cold air sensor, and water temp sensors?

Thanks Ramon!

With the initial diagnosis (before sending in the DME for repair the first time), there was an issue where we were seeing voltage readings from the Coolant Temperature Sensor (good values) but at the same time the data stream was showing something like a -200 degree C reading. So on one line the scanner is showing a good voltage for the sensor (good CTS circuit) but the DME translation was was at the bottom of the temperature scale. When the 1st DME was repaired (that voltage regulator), this issue was corrected. So, again it looks like a "logic" problem. The votage values are there, but the DME isn't translating properly.

The air temp sensor never showed an issue.

[MBXB]

Check here:

http://ecubb.bmwecu.org/board/

Someone may have a hack or be able to suggest one.

[ryan roopnarine]

you're the third florida person with das bmw I know of that has a fried ecu. my uncle, the general purpose mechanic, says that he sees it on a semi-regular regular basis. i'm thinking that perhaps it has to do with rainwater or such.

[Paul in NZ]

you're the third florida person with das bmw I know of that has a fried ecu. my uncle, the general purpose mechanic, says that he sees it on a semi-regular regular basis. i'm thinking that perhaps it has to do with rainwater or such.

i m sure there are wetter paces for E34s than florida....lightning perhaps?