Hoping for some wiring help on my 87’ swapped with a 2004 5.3 out of a Silverado. It’s wired up using a hawks harness. I can not get the temp sensor to work I’m getting a po118 code and it’s reading out at -38 degrees. I don’t have a 5volt reference at the sensor so I ran new wires back to the ecu. A Haynes manual I have for the truck said it should be pins 42/33. After running new wires I still don’t have 5 volt reference at the connector and it’s still reading -38 degrees. I’m wondering if it’s possible my harness is pinned wrong/ or the manual is wrong. Or I’m just missing something. Thanks in advance

 

Those are 2 wire temperature sensors. They won't have a 5v reference at all. You'll have ground and signal back to the ECU. You've either got a bad sensor or bad ground

 

This is such bad advice.

 

Lol get back on the nearest school bus. It's a 2 wire sensor. 3 wire will have your 5v reference, ground, and signal back to ECU

 

So first thanks for the help so far everyone that’s replied. So an update on the temp sensor:
I bought a O’Riellys replacement sensor-no change.
Got a OEm Delphi one from another truck-no change.
Got a new connector-no change
Checked all grounds and directly grounded the sensor to the battery-no change

I heard that maybe swapping out to a 3 pin Camaro style might help, and without a completely accurate pinout to test wires im lost on the best next step

 

Three pin sensor won't tell the PCM anything that a two pin sensor can't. The third pin is just to run a factory gauge.

The grounds have NOTHING to do with CTS operation. The wires originate from the PCM. It sounds like you've either got a bad PCM (possible), or a bad harness (much more likely).

 

Definitely going to have to look at the wiring.

Also do not use a dirty ground for sensor circuits.
Use the PCM Sensor Ground Circuit or a direct battery connection.

 

ECM likely has diagnosed an open circuit and defaulted to cold temp limit. There is a broken or detached wire somewhere in your harness, or pinned out at the wrong location.

Connector at the CTS should have letters A and B embossed on it. Pin B is signal from ECM, wire might have some yellow color on it. Pin A is ground return back to ECM, wire might have some black color on it.

I don't know pinouts at ECM off top of my head. You'll need to reference a wiring schematic for the donor vehicle