13$ OBDII scan tool solved severe hesitation prob?

[antiqueshell]

While just disconnecting the battery to reboot the ECU didn't work with my situation, after I had a terrible hesitation problem on acceleration, the car idled fine, and seemed OK when cold, but as soon as the engine would reach normal operating temperature the car literally would stall when taping the gas pedal. I looked at all the obvious issues with temp sensors, distributor, rotor, cap, ect...finally I was focusing on the fuel pump. Well before I threw down 400$ for a new pump I was playing with my basic read and clear universal OBDII scan tool. I accidentally left the ignition in accessory position (not supposed to do this when plugging in the code reader to the port) and saw the reader oddly show something it shouldn't have (reseting all ECM values to factory) and it automatically proceeded. Well right after that I went to start the car and viola, no more hesitation problem. I don't know what happened but it solved the problem and that 13$ scan tool is NOT supposed to be able to do a reset of all ECM parameters to factory values. But it did, and it worked...anyone else have an experience like this? Car was a 1996 VW Golf 2L.

Just to add the issue had been plaguing the car for months and never changed during in characteristics during that time.

 

[bullwinkle]

OBD II won't reset with a simple battery disconnect (that's OBD I), but at least now, you have a starting point, if it throws a code or acts up again you'll have a better idea where to look.

 

[KDonkey]

Some ECU will clear most or all adaptions when fault codes are cleared. That's just what they do.

 

[Leo99]

Congrats on fixing it!

 

[antiqueshell]

Originally Posted By: KDonkey
Some ECU will clear most or all adaptions when fault codes are cleared. That's just what they do.


Really, I thought that clearing a code at least with my early
OBDII car only erased the fault code, not changing any engine parameter settings.

There was ONE code. P0327 Engine knock sensor low voltage.
But the sensor and wiring were fine. I checked that.

Car has been fine now for about eight months and counting , no more occurrences since then.

 

[KDonkey]

If you go look at the I/M or readiness monitors after clearing fault codes you should see that many of them go back to 'not ready.' The instruction to clear fault codes is kind of a signal to the computer that some work has been carried out. They all act differently according to manufacturer, but my experience with Bosch boxes of your vintage are that at least the fuel/air adaptations are cleared.

 

[antiqueshell]

Thanks for the heads up KDonkey!

I had no idea that clearing the code and MIL light would reset
adaptations like that, nice to know.

So do the later boxes not do that without a more specific instruction?

Odd that I had that P0327 and there were no actual problems.

 

[antiqueshell]

Originally Posted By: Leo99
Congrats on fixing it!


Oh, I don't deserve congrats since it was purely dumb luck.
In any case a very weird problem.

 

[KDonkey]

Originally Posted By: antiqueshell

So do the later boxes not do that without a more specific instruction?


I'm not exactly sure because I don't know of any rules about this, and I don't have any cars that are much newer. Sometimes you get an indication of this if you command it to clear fault codes while the engine is running at idle, such as idle speed jumping up or down slightly for a moment.

Almost every dealer scantool has a specific command to reset adaptations. Many of the boxes will also forget adaptations when the battery is disconnected for some time.

I believe that resetting adaptations when a generic OBD2 tool commands to clear fault codes is a good practice and is in the spirit of the OBD2 mandate.

An automatic gearbox usually learns adaptations too (for instance pressure modulation during shifting.) The one on our Volvo (which is actually a toyota gearbox), which I have been working on a bit lately, will also reset when faults are cleared from the ECU.

 

[antiqueshell]

The only other thing I can think of that MIGHT have factored in is that the battery had NOT been disconnected from the car in over
six years! I didn't remember this until I checked the battery receipt....I almost wonder if like Windows from time to time that software needs a reboot or something like it over time, perhaps some adaptations became corrupted at some point. Perhaps errant static electricity during a t storm or ?

 

[eljefino]

Some dodges had problems with a bad ECM ground. A scan tool "bridges" ground between ECM and chassis, and sometimes its simple presence improves sensor readings and performance.

 

[antiqueshell]

Originally Posted By: eljefino
Some dodges had problems with a bad ECM ground. A scan tool "bridges" ground between ECM and chassis, and sometimes its simple presence improves sensor readings and performance.


But that doesn't explain why things eight months later seem to be fine, you'd think that by now the poor ground might have reoccurred and had the ECM learning the trouble causing adaptations again.

 

[Leo99]

Originally Posted By: antiqueshell
Originally Posted By: Leo99
Congrats on fixing it!


Oh, I don't deserve congrats since it was purely dumb luck.
In any case a very weird problem.

Dumb luck or not, you fixed the problem. Sometimes those electronic gremlins just won't behave and cars have weird problems that won't go away despite a lot of time and money and sometimes you get lucky and fix it with a $13 tool by accident. Better to be lucky than good, I always say.