0.3 volts at serial port ? Bad ECU?

[Spoolin98]

I can?t connect to this ECU because of a ?no power detection? issue . The ground is good and straight to the negative side of the battery for testing . I am not able to get 0.3volts at the signal wire . Could this be a bad ECU ?

[blindsquirrel]

Which 'signal wire'? What parts are you dealing with? What is 'this ECU'? Sorry for the questions, my crystal ball is in the shop for scheduled maintenance.

[vettemakesemwet]

Magic eight ball says you're f****d. Do you mean pin 16 of the obd port, typically reserved for B+ voltage to power scan tools and the like? Magic eight ball asks for more information. Snap on midget needs to know what kind of coffee you have before he'll crawl into the magic land of the crystal P59 and tell us any more. The Squirrel Master asks valid questions. We are not mind readers. Seems like some of us are smart assed damn good guessers at times though.

[blindsquirrel]

It's not generally useful to try measuring DC voltage on a line carrying digital data streams. If you get anything, it won't mean anything. It won't tell you whether the data stream is 'live' or transmitting anything valid. It'll only prove out that it's not shorted to some other power/ground circuit.

Pin 16 is supposed to be B+, constant battery, unswitched. Most times no power at the DLC is a blown fuse. DLC B+ is not supplied by the ECM, it comes from a regular fused source.

[blindsquirrel]

BTW, that pinout is from a 2004 Silverado, in case anybody in this sad phone-addicted Twitterized world still cares about trivial distractions like year/make/model when looking for diagnostic info.