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Very true Mike, and although I might not get the opportunity on this occasion to use a Pico on it, there be other opportunities I'm sure where I can use it and a video presentation as well.AuthorMike wrote:Any update on this, sounds interesting.
If only a PicoScope was owned & used, this has the makings of a great case study.
Thanks Liteace. I was not sure whether the car was being taken by the customer or not, but today it seems the car has been left with me, so after I speak to the customer, hopefully I'll see this through to the end.Liteace wrote:Check ALL ecu supply voltages, could have one missing, fuses, there's 3 or 4 on this for engine ECU supply
So we have female driver, and an engine that starts up and is driveable albeit with an EML and running not as well as it should.The car is a Mini R56 engine N12B14A. The customer was complaining about the engine running rough, she advised the revs would go up and down while driving.
two such codes were present, they were;
1 / 2A56 - Oxygen sensor heating after cat malfunction, and
2 / 2B68 - Air Mass Flow plausibility.
No !! Not with the Engine Running, particularly when cold. I get the "No VD if No Current Flow" theory. Add to that you do not have the Prerequisites in place if you are testing an O2 with it switched off. Checking pulses in a cemetery - it would be a labour of love with little fruit.Referring to the manufacturer technical data working from the ECU connector (back probing) terminal B17 according to the wiring diagram advised that B17 should supply battery voltage from the ECU to the heated oxygen sensor terminal 1, which should also while connected supply battery voltage to ECU B18.
It proves the law of VD - nothing more of relevance with the fault code you have.This is a good check to be completed from the ECU terminals because it not only checks the continuity of the wiring, but also the heater circuit through the lambda sensor.
Really, that would be incredible !!The voltage was recorded at 1.31V at both ECU terminals B17 and B18.
Far from established! Lots of graft to do before that can be a twinkle in your eye.At this point I am leaning towards an ECU fault, but not yet established.
With the engine idling the ECU should provide a PWM signal from terminal B18,
The heater runs at NBV not 5v, that should dictate your settings. 0.5 s is too much time across the screen to see the plausibility test and rejection, not that Voltage would show that. The ECU employs other, more meaningful means to rule over the territory that is the eternal ruler of.the reference voltage and time being 5V/0.5 sec. The oscilloscope did not trigger at all
Not capable or not willing ???at these settings, only when I altered the scope voltage settings to 0.2V/0.5 sec did the trace appear, but the amount of hash/noise clearly indicated to me that the ECU was not capable of providing a PWM signal.
So it can work without a heater in another galaxy (not a ford galaxy) ???As the oxygen sensor on this car creates its own voltage when the temperature rises, this I based my understanding on the fact that the sensor produced no voltage at terminal B24 until the engine temperature warmed up, the actual voltage was greater than the Bias voltage I had previously observed on the VERUS at 0.75 V fluctuating, the technical data advising around 0.6V. The oxygen sensor had a good ground connection showing zero volts,
and the ECU terminal B29 linked to B17 was also recording 1.31V.
Does it matter ?? Heater circuit's are not dissimilar on any of them - just like an electric soldering irons or glow plugs. schoolboy physics. I speak for myself.I am convinced the type of sensors fitted are the Zirconia dioxide type.
You would need to have studied the strategy of the hook, what is its criteria for a hot shot pass or fail ? Does it vary for individual circuit load or is it Dumb to that.I'm not sure what electricians might think the differences are between testing wiring using a voltage supply and a bulb against the HOOK,
however initially I decided to take the safe option and check the wiring using the ohmmeter, the only readings that I was able to establish were 0.00 ohms, at this point I was confident that the wiring harness was in good working order, so then as a second test I used the HOOK and load tested the wiring, then checked with the ohmmeter again recording 0.00 ohms.
17 and 29 fire up both O2's and all 4 injectors - tell me the car starts and idles just one more time - Please I beg you !!!My conclusion to this diagnosis is that the ECU is not supplying a voltage from terminals B17 and B29 to the lambda sensors,
Very true - Cause or Consequence ??nor is the ECU providing a PWM signal from B18.
Oh dear, you use A.D for wiring diagsSTC wrote:
B17 & B29 (Kind thanks to Autodata) Push B+ to Both O2's and all 4 Injectors.................................
I have WDS, ICOM, and an Account with BMW Tech Info. Just shout if you need any thing.Liteace wrote:Oh dear, you use A.D for wiring diagsSTC wrote:
B17 & B29 (Kind thanks to Autodata) Push B+ to Both O2's and all 4 Injectors.................................
A blown fuse would display the same symptoms. Some times we don't know what we don't know yet mask it behind 100 years of experience, 100 years of getting It wrong qualifies as experience.Dcunning35 wrote:This is confusing me the lack of pwm control of a post cat oxygen sensor ,not sure how this can effect fueling if shorted yes if linked to upstream heater I have seen lots of drops in upstream o2 sensors caused by downstream circuits an easy spot with the pico.
Has the air mass plausibility dtc returned or either dtc when cleared .
Have you any freeze frame data in conjunction with dtcs
Danny