Data loss

badsavana · June 25, 2014

Can anyone tell why this happens. I dont think this is normal.

&CDFiXER% · June 25, 2014

Id vote for your data logger hardware interface is losing connection to the vehicle ECU or to your phone/tablet/laptop.

Some chipsets or the way they are implemented will do that.

Try it on another vehicle. If you get the same thing then it is the OBDII adapter.

badsavana · June 26, 2014

Never had that happen before on this van. I'm trying to find out why my truck is layin over and came accross that. Here is another one where it spikes for 25 seconds.

Doug_Scott · June 26, 2014

Personally, the screenshots do not contain anywhere near enough information to even figure out what data is being displayed. Can you explain what the graph is actually showing? What leads are showing "no data"?

As someone else offered, have you run your device on another vehicle since this showed up on your vehicle? Reason being, your scan tool can go bad at any time, and if it just went bad, you maybe chasing the wrong end of the problem. Plug your device into a different vehicle, and run the same test. Compare results between the two vehicles, and take note of where differences first showed up. If you get the same result, then the issue is somewhere between the ODB-II connector and keypad on your scan tool.

badsavana · June 26, 2014

Nothing wrong with the data logger. Passed every test I could throw at it. No anomalies on any other vehicle or self diagnostic test. What you see is what it is logging.

badsavana · June 27, 2014

Maybe short in harness or connector?

&CDFiXER% · June 27, 2014

Could be, maybe the power to the diagnostic connector is dropping out?

Not sure how the data would show this but since you mentioned the vehicle running poorly, perhaps something is affecting the grounding or power feed to the sensors that are feeding the ECU that are being shown on your data logger. Any CEL's and/or codes thrown? Or, way out there, something causing the ECU to go open loop and that is causing the data to do that yet not throw a code.

badsavana · June 28, 2014

I have been over all of the grounds, even added one because I didn't like the looks of one. I have removed every connector and hosed each end down with crc. Changed several connectors because the pins looked corroded. Tested every sensor that I could think of that could even remotely cause it to lay over. I have run multiple scans and this is the first time that I have seen the data drop out.

What is weird is that not all of the data dropped out. It is clearly evident, by reading the description of each sensor imput, that there is something funky going on with both aft sensors. The response time is far from normal. Now is that the sensors failing, how likely is it for both to fail simultaneously, or is there something going on with the harness or pcm.

I have no way to diagnose the pcm but I do have a dmm to ohm out the harness. That should be a joyfull proscess. Try getting to the pcm with the hydraboost in the way.

And all the while my issues are intermitent at best.

It has never run well and I have just dealt with it but lately it has been getting more pronounced.

Never has thrown a code, that would be to easy.

Logger shows closed loop at that event.

Layed over real bad right after that event in screen shot 1.

daxr · July 2, 2014

I'm not an expert enough to say for sure, but it looks like you may have simply lost the signal from the MAF sensor, and the other signals react predictably in response to that. You can use the DMM to probe the MAF sensor signal directly, and verify that it agrees with what the scanner is showing.

badsavana · July 3, 2014

I thought about that and got some funky results when I tested that MAF. Then I saw that and am second guessing myself. A MAF is kinda pricey and I really don't want to just throw parts at it to see what sticks.