'89 rs with a 350 tbi swap.
1228746 ecm with correct chip.
When I try to datalog; the cts reads -40C.
I have checked out the cts and wire to the ecm with a meter.
I can read the cts @ the ecm connector with a meter.
I have a good ground @ the cts sensor connector.
The ECM "refuses" to see the cts sensor?
Anyone ever have this problem?
I am setting a code 15 (coolant temp sensor -27 degrees after engine has been running for more than 30 seconds),,not surprised here,,,it reads -40C "always"
thank you
mike

 

Never mind; I was a little "hasty" on my diagnosis.
I cut the wire @ the ecm and put a 300 ohm resister on the yellow wire.
The other end of the resister went to ground.
Warmed up the car and it ran perfect,,no trouble codes and the datalog read 170 degrees. So; I have a wiring problem from the ECM to the cts.
Now to completely expose the harness and find the bad spot.
The only thing I can think I did wrong; was, maybe,,, when I thought I was reading the cts @ the ecm connector,,,I was reading the resistance through my fingers and instead of 300 ohms or so; I was actually reading 30M ohms or so, and I didn't see the decimal point on the DMM?? It has happened before.
It's amazing how a nights sleep can change a problem.
Thanks
mike

 

The reading of -40 is from an open circuit. It could be the sensor is open or the wire is open, or the engine block ground for the sensor is open.

At 72*F the resistance of the sensor is around 3200 ohms.

RBob.