Are you saying you already swapped out the KR75 powertrain relay and this did not correct the issue?If you did not swap out this relay this is most common for this code to set here with it needing replaced.Below is the diagnostic procedure and info on this code and circuit.
The powertrain relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the switch contact at all times. The engine control module (ECM) supplies the ground path to the relay coil control circuit via an internal integrated circuit called an output driver. When the ECM commands the powertrain relay ON, ignition 1 voltage is supplied to the ECM, and to several additional circuits.
If the relay fails to close, the engine will not crank.
1. Ignition OFF, disconnect the KR75 powertrain relay.
2. Verify that a test lamp does not illuminate between the ignition voltage circuit terminal 87 and ground.
◊If the test lamp illuminates, test the ignition voltage circuit for a short to voltage. Also test for a short to voltage on the circuits to the following ECM terminals:
3. Connect a DMM set to the diode setting between relay control circuit terminal 86 and ground. Verify the DMM displays OL.
◊If not the specified value, test the relay control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.
4. If all circuits test normal, replace the KR75 powertrain relay.
Let me know if you need anything else and feel free to rate my help here as this is how I receive credit for my time.A 5 star rating is appreciated.Thanks Pete