HarleyTechTalk

Quote from: FSG on April 07, 2013, 04:09:41 PM
True, but do you think that Tuning Mfrs would want to skate on that thin ice, that is if the're not on it already.   

I think I've pushed that accept the offroad button use a few times today.
Ron

I think that the heaters DO, in fact oscillate.  Why else having a 'heater circuit' and not an on off with a key on?

What CAN be happening, I have NO clue but logic here, that maybe the controller varies the amperage? Like Joe suggests.  amperage could be used as an equal method as volts to warble a heater.

I DO know that a heater, if unplugged, throws a code in a car.  That being the case....  that logic tells me SOMETHING is being monitored.  A heated metal will have less impedance, as compared to a cold metal, especially some weird kind of bimetallic.

Google?

Quote from: wurk_truk on April 07, 2013, 05:10:26 PM
I think that the heaters DO, in fact oscillate.  Why else having a 'heater circuit' and not an on off with a key on?

What CAN be happening, I have NO clue but logic here, that maybe the controller varies the amperage? Like Joe suggests.  amperage could be used as an equal method as volts to warble a heater.

I DO know that a heater, if unplugged, throws a code in a car.  That being the case....  that logic tells me SOMETHING is being monitored.  A heated metal will have less impedance, as compared to a cold metal, especially some weird kind of bimetallic.

Google?

One way to find out. Slap a multi on the heater wire to ground and see if it remains constant. My money is it will. Throwing a code is why PV has an O2 heater on/ off switch. It prevents the ecm from throwing a code when deactivated in the software.
Ron

Would need an amprobe to find this out, NOT a VOM without that, and one that works >1 amp ranges is NOT in my tool box.

Also, one must be very careful on what ground they attach a probe to.  It MUST be the same ground as used by the ECM...  we call them clean grounds.  Or... you introduce the potential between the two grounds into the equations. There IS a need to be careful.

The controller works by varying how much grounding takes place, NOT whether the 'hot' side changes voltage.  It is the GROUND side that changes in these systems.

What some miss is... the 'heater plus" will ALWAYS be hot AND at the same voltage.  Just like an O2 sensor circuit.  Look at the circuits on a schematic.  Hots are shared, and grounds come back to the ECM separated.

So... what is TRULY needed is to find an unused 5vdc GROUND off of the ECM and see if there is a potential as compared to the heater grounds.

Don't wish to toast something with very small voltages, etc, THRU a meter probe.

I will get my scope back and see if that can be used for amps.

Quote from: wurk_truk on April 07, 2013, 05:46:57 PM
Would need an amprobe to find this out, NOT a VOM without that, and one that works >1 amp ranges is NOT in my tool box.

Also, one must be very careful on what ground they attach a probe to.  It MUST be the same ground as used by the ECM...  we call them clean grounds.  Or... you introduce the potential between the two grounds into the equations. There IS a need to be careful.

The controller works by varying how much grounding takes place, NOT whether the 'hot' side changes voltage.  It is the GROUND side that changes in these systems.

What some miss is... the 'heater plus" will ALWAYS be hot AND at the same voltage.  Just like an O2 sensor circuit.  Look at the circuits on a schematic.  Hots are shared, and grounds come back to the ECM separated.

So... what is TRULY needed is to find an unused 5vdc GROUND off of the ECM and see if there is a potential as compared to the heater grounds.

Don't wish to toast something with very small voltages, etc, THRU a meter probe.

I will get my scope back and see if that can be used for amps.

Theres a test procedure in the link I posted yesterday . It shows ground as the control, just like you say.
Ron

Quote from: hpulven on April 07, 2013, 02:29:55 AMA PID controller would normally
try to stabilize the output from the sensor on
the target level, the ecm is doing something else,
it is driving the system to oscillate around the
target level

The sensor response it too sensitive. It will never "stabilize" on a running engine. That's why it oscillates from the PID control. Yes, it is PID control. I put stabilize in quotes because oscillating around a target value is, in fact, stabilized.

   Its actually the loop response error. All
Closed loop systems have an error, some greater or lesser. It depends on the designed loop response and damping factor.

Obviously the ECM monitors the current flow through the heater for diagnosis purposes, throwing a code if it detects that the  current is above or below a specified range.  While it's possible, I doubt the ECM is varying the current to the heaters so as to control their temperature.

Ok got it. Now how can we apply this information to improve O2 sensor performance and lessen deterioration of closed loop feedback?
Thanks for your patience,
Bob