Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
The DTC can be cleared by using the scan tool Clear DTC Information function.

DTC P1668

Step	Action	Value	Yes	No
Schematic Reference: Starting and Charging Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views in Engine Controls - 3.6L (LY7)
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Install a scan tool. Turn ON the ignition, with the engine OFF. Wait 5 seconds. Start the engine. With a scan tool, monitor the DTC information for DTC P1668. Does the scan tool indicate that DTC P1668 has passed?	-	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Turn OFF the engine. Disconnect the generator harness connector. Start the engine. Measure the pulse width modulation (PWM) signal between the generator turn on signal circuit and ground. Is the PWM signal within the specified value?	15-87%	Go to Step 5	Go to Step 4
4	Test the generator turn on signal circuit for a short or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 10	Go to Step 5
5	Test the generator battery positive voltage output circuit for a high resistance or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 10	Go to Step 6
6	Inspect for poor connections at the harness connector of the generator. Refer to Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 10	Go to Step 8
7	Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 10	Go to Step 9
8	Replace the generator. Refer to Generator Replacement (L26) or Generator Replacement (LY7) . Did you complete the replacement?	-	Go to Step 10	-
9	IMPORTANT: The replacement ECM must be programmed. Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming.Did you complete the replacement?	-	Go to Step 10	-
10	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?	-	Go to Step 3	System OK