Okay, sorry for the delay, so much going on lately,
So, for simplicity and clarity, the ECT signal wire from the sensor's two wire connector goes to ECM pin 7, the other wire goes to ECM pin 46 (SIG RTN- Gnd).
The Air Charge Temp Sensor's signal wire goes to ECM pin 25, and its other wire also goes to ECM pin 46 (SIG RTN-shared Gnd).
The purpose of disconnecting the ECM connector and each sensor's connectors is to isolate each wire, so you measured from the ECT signal wire to ECM pin 7 with the sensor disconnected and the ECM disconnected and got 85 ohms, if that's the case then there is high resistance on the ECT signal wire going to ECM pin 7,
But these wiring diagrams don't show any possible connectors in between the sensors and ECM, so you will have to note the wire color and try to follow it as best as possible. My diagram below also shows how to check each wire for a short to ground, but also not knowing the wiring harness's routing, makes it a bit more difficult. Most of the time a sensor Ground like this will be a direct wire to the ECM, so not grounding to the engine block first like many other grounds are done. This is to preserve the sensors signal quality. The high resistance can be and is most likely corrosion somewhere in the circuit. Ie inside a connector or even a pin hole in a wire can cause it to corrode inside and it just grows right inside the wire insulation. This usually causes the insulation to discolor in places but can be difficult to spot.
You'll have to excuse my artwork below, but this should help simplify testing. Let me know what else you find, I apologize if you need to retest, it's not always easy to explain circuit testing. The method I would use is even more difficult with load testing a wire, but stick to resistance testing for now, since it sounds like you're onto a wiring issue here.
Image (Click to make bigger)
Sunday, February 2nd, 2025 AT 10:38 AM