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I have a 2000 Dodge Dakota 3.9. As the topic stated I am not getting 12v to my O2 sensor's heater circuit. I am stumped as to why not. When I trace it back to the power distribution center, the 15a fuse that supposedly feeds it registers as a ground for some reason (figure that one out). Since my truck uses an isolated circuit to power the 02 sensors (neither hot nor ground go through the PCM) could I run my own "key on" 12v power supply to the heater side to get it to power up? Or would that screw something up I'm not thinking of? and if I can, could I just cut the wire and crimp mine in its place? IO have got to figure this out or my truck will be illegal real soon. Thanks in advance for any help. -Tom
If the circuit isn't energized it'll test as a ground because it's got a low resistance path to ground thru' your O2 sensors. Since it's fed by the ASD are you testing KOEO or KOER?
Matt T is right on. Fuse 15 is powered by the ASD relay, which will only be closed during engine cranking and running. You'll need to do your testing with the engine running.
You absolutely could run your own heater power wire. But, you'd also end up powering the injectors and the ignition coil, which would defeat the purpose of thr ASD relay. :silly: I've worked on trucks like these with voltage backfed into the ASD circuit. They do weird stuff...
