Here is the rest of the procedure for code P0054.See if you can follow it.I suspect this is still a wiring issue or internal ecm fault needing repaired or replaced with the issues described here.
4. Engine running, leave the test lamp connected from the previous step. The lamp should flash or be ON steady.
^ If the test lamp is not ON steady or flashing, test the HO2S heater low control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
* The output driver should detect a short to voltage and turn OFF. If a resistance fault is present the driver will remain ON and the scan tool will display more than 0.0 amp. Less than 10 ohms may set a DTC.
* Performing this test may set additional DTCs.
5. Ignition OFF, install a 30A fused jumper wire between the appropriate HO2S heater voltage supply circuit terminal D and the appropriate HO2S heater low control circuit terminal listed below:
* B1S1 terminal E
* B1S2 terminal C
* B2S1 terminal E
* B2S2 terminal C
6. Engine running, verify the appropriate scan tool HO2S Heater parameter is less than 0.1 amp.
^ If more than the specified range, test the HO2S heater voltage supply and HO2S heater low control circuits for more than 1 ohm. If the circuits test normal, replace the ECM.
7. If the ECM and all circuits test normal, replace the appropriate HO2S.