Cleaned the connectors. No real visible crud, but hit them with some contact cleaner and let them air dry. No improvement.

Ran the OBD2 codes. Only one present: p0118. Temp sensor over volt.
But the engine is cold, obviously.

OBD2 is connecting to PCM.
Found the temp sensor was busted, so I pulled the stub out of the harness and ordered a new pigtail/sensor combo, since the pigtail looked pretty beat up.

 

Hhhhmmm.... Think I would be tempted to check the rest of the 5 volt sensors, and see if any of the others are getting 11 volts instead.....

 

Inquiring minds...etc. Which lead did you get that reading on, and was it plugged in? I'm assuming it was the sense lead to ground, but wondering if trying to read resistance with power applied is a valid test. Not criticizing, just never thought of doing it that way.


Did you chase down that voltage on the sensor? That is a common reference voltage to several sensors, I believe. Curious to know what happened.

 

Power to fuel and asd. Relays check good when I trigger them with 12v from battery.

Was this with them in or out of the circuit? They normally get power thru fuses and are triggered by ground from the PCM.

 

Checked resistance on the crank sensor with it unplugged and pulled from the engine. 1.0 then .690 when tripping the magnet with a bit of steel.

It's still 11 volts to the crank sensor plug. I haven't traced it yet. Been doing other things on the truck.


Power with key on showed power to the key on powered lugs, relays removed.
Relays were checked with a jumper wire while off the panel and in hand.
Fuel pump was checked with relay out and a jumper wire from key on b+ to green/black at the relay lug.

Fuel pump works when jumpered. Relays work when remotely jumpered.

 

I have never checked the resistance on the sensor but, to me, that variance in resistance is not much. I would think that it would almost infinity then to about 1 ohm when triggered.

 

That's what I thought too, which is why I included it in my diagnostic data here.

 

I don't know why I didn't think of this before, but the easiest test of the Hall Effect Sensor is to have 5v on pin 3 and ground on pin 2 and pass metal between the magnet and the pickup like you did with the resistance. The sensor lead (pin 1) should switch between 5 volts and zero.

 

I got the no bus problem squared away. It was a(nother) bad ground. Now it's having a weird issue in the starting cycle where the starter won't go, but there's a loud click, the gauges go weak, and the fuel pump relay starts clicking like crazy.

Out of the frying pan. Into the fire. Thanks for the help, y'all.

 

Sounds like a weak battery.