Elsewhere on GMTNation and straying off the topic of that titled thread...
A post in thread 'P10 PCM 5 Volt References' https://gmtnation.com/forums/threads/p10-pcm-5-volt-references.21534/post-634636
All that being said,,, a wondering of mine is unaddressed....
"why is there a negative voltage relative to chassis/frame/signal ground seen on both leads of a CKP sensor?"
The voltage relative to PCM/frame ground is always nearly identical on both leads and I have seen it vary from -2.39 volts right after initial power-up up to -11.33 volts this morning after maybe 24 hours of 'operation'.
These observations of mine suggest the negative voltage strays higher as the PCM is left powered up but idle for longer times perhaps.
There is a 4.5 millivolt voltage seen between the two PCM CKP leads, and the resistance between the two leads when unpowered is in the range of 48 or 49k ohms in both polarities.
Some qualifications are: the subject PCM is powered up on the benchtop with no other connections but serial data and a single test lamp on a single fuel injector control terminal.
Unrelated.... If I repeatedly touch either lead from the PCM CKP sensor terminals, every now and then the test light on the fuel injector control wire lights up indicating fuel injector activity. This was unexpected.
Maybe at some level there is an attempt at isolating the CKP signal from possible electrical noise/interference? And the voltage I am seeing is just some stray anomoly? The voltage is steady and looks pure on a toy/hobby scope.
A post in thread 'P10 PCM 5 Volt References' https://gmtnation.com/forums/threads/p10-pcm-5-volt-references.21534/post-634636
All that being said,,, a wondering of mine is unaddressed....
"why is there a negative voltage relative to chassis/frame/signal ground seen on both leads of a CKP sensor?"
The voltage relative to PCM/frame ground is always nearly identical on both leads and I have seen it vary from -2.39 volts right after initial power-up up to -11.33 volts this morning after maybe 24 hours of 'operation'.
These observations of mine suggest the negative voltage strays higher as the PCM is left powered up but idle for longer times perhaps.
There is a 4.5 millivolt voltage seen between the two PCM CKP leads, and the resistance between the two leads when unpowered is in the range of 48 or 49k ohms in both polarities.
Some qualifications are: the subject PCM is powered up on the benchtop with no other connections but serial data and a single test lamp on a single fuel injector control terminal.
Unrelated.... If I repeatedly touch either lead from the PCM CKP sensor terminals, every now and then the test light on the fuel injector control wire lights up indicating fuel injector activity. This was unexpected.
Maybe at some level there is an attempt at isolating the CKP signal from possible electrical noise/interference? And the voltage I am seeing is just some stray anomoly? The voltage is steady and looks pure on a toy/hobby scope.