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Engine Management – V6 – Diagnostics Page 6C1-2–218
6 1 Test the pump current circuit of the HO2S for an Did you find and correct the condition? — Go to Step 11 Go to Step 8 7 1 Test for an intermittent and for a poor connection Did you find and correct the condition? — Go to Step 11 Go to Step 9 8 1 Test for an intermittent and for a poor connection Did you find and correct the condition? — Go to Step 11 Go to Step 10 9 1 Replace the HO2S. Refer to 6C1-3 Engine Did you complete the replacement? — Go to Step 11 — 10 1 Replace the ECM. Refer to 6C1-3 Engine Did you complete the replacement? — Go to Step 11 — 11 1 Use Tech 2 to clear the DTCs. 2 Turn OFF the ignition for 30 seconds. 3 Start the engine. 4 Operate the vehicle within the Conditions for Did the DTC fail this ignition? — Go to Step 2 Go to Step 12 12 1 Using Tech 2, select the DTC display function. Does Tech 2 display any DTCs? — Go to the appropriate DTC Table in this Section System OK When all diagnosis and repairs are completed, clear all DTCs and verify correct operation 7.61 DTC U0001 DTC Descriptor This diagnostic procedure supports DTC U0001 – No Communication with CAN-Bus (High Speed). Circuit Description The engine control module (ECM) communicates directly with the control modules connected to the GM LAN serial data However, the immobiliser control unit (ICU) communicates with the ECM using the keyword 2000 protocol. Since the GM DTC U0001 sets if the ECM detects a fault condition in the serial data communication circuit. Conditions for Running the DTC DTC U0001 runs continuously when the following conditions are met: The ignition voltage is 10.0 – 16.0 V. The vehicle power mode requires serial data communication. |