Tracing a short or ?

[jpowel29]

Coolant temp shows maxed out hot as soon as you turn the key on. Sensor is new and ohms out as it should cold. Checking the engine harness (which is nearly new) the multimeter doesn't find any short. The pins/slots on the bale connectors are clean and tight and not bent/damaged (including the large connector that attaches to the ECM with PIN 74 (which I believe is the correct one for ECT on the LBZ). I will pull the ECM out next and inspect that pin. If it's bad or if it's good, any suggestions or thoughts?

 

[Chevy1925]

With a Scan tool hooked up, will it read temps correctly?

 

[onebaddmaxxx]

Should be throwing some kind of code if sensor is bad. When ECT is that hot power in the tune is reduced greatly. Do a gauge sweep with a scan tool

 

[jpowel29]

Don't have a scanner yet. Has code P0652 that won't clear so I need to check some other 5V wiring and grounds. Truck will not start or crank over for very long in this condition. unplugging the engine harness bale connector and it cranks over fine.

 

[jpowel29]

truck isn't overheated - this is the initial start-up after engine install

 

[onebaddmaxxx]

I know its not that hot, but I'm saying if its showing that hot, the engine would be depowered.

 

[onebaddmaxxx]

This is gm's diag flowchart for the code you listed, none of which seem to be a cause for the ect issue. I was originally asking are you sure the cluster is showing proper.

Turn OFF the ignition for 30 seconds or until the ECM powers down.
Disconnect the accelerator pedal position (APP) sensor.
Turn ON the ignition, with engine OFF and measure the voltage from the 5-volt reference circuit of the APP sensor 2 to a good ground with a DMM.
If the voltage measures 4.7–5.2 volts, replace the APP sensor .
With the DMM still connected to the 5-volt reference circuit, disconnect all other components connected to the 5-volt reference 2, one at a time.
If voltage changes when one of the above components are disconnected, replace the component. Refer to the appropriate replacement procedure.
Test the 5-volt reference 2 circuits for a short to ground or a short to voltage.
If no problem was found in the 5-volt reference 2 circuit , replace the ECM.

 

[jpowel29]

Thank you for that heads up and I understand what you are saying. I will check that as well but I may have found an issue as well. The harness from the oil pressure sensor is pinched (got in between the power steering reservoir and the head. Once I check that I'll follow the rest of the troubleshoot sequnce.

 

[jpowel29]

The harness going to the oil pressure/level sensors looks ok, only slightly crimped but no wires broken or chaffed.

 

[onebaddmaxxx]

Make sure no sensors have a lot of tension on them as well

 

[jpowel29]

Found the short and the truck fired right up. Thanks for the help!

 

[cdbright]

well now i gotta now where the short was