Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. 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 P1638

Step	Action	Yes	No
Schematic Reference: Starting and Charging Schematics Connector End View Reference: Engine Controls Connector End Views in Engine Controls-5.7L, Power and Grounding Connector End Views in Wiring Systems, or Engine Electrical Connector End Views
1	Did you perform the Engine Electrical Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - Engine Electrical
2	Install a scan tool. Start the engine. With a scan tool, monitor the DTC information for DTC P1638 in Engine Controls. Does the scan tool indicate that DTC P1638 has passed?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Turn ON the ignition, leaving the engine OFF. Disconnect the generator harness connector. Connect a test lamp to battery positive voltage and repeatedly probe the generator field duty cycle signal circuit in the harness connector while monitoring the GEN F-Terminal Signal on the scan tool. Is the Generator PWM display affected?	Go to Step 5	Go to Step 4
4	Test the generator field duty cycle 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 8	Go to Step 6
5	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 8	Go to Charging System Test
6	Inspect for poor connections at the harness connector of the PCM. Refer to Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 8	Go to Step 7
7	IMPORTANT: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls 5.7L.Did you complete the repair?	Go to Step 8	-
8	Review and record the scan tool Fail Records data. Clear any DTCs. Operate the vehicle within the Fail Records conditions as noted. Using a scan tool, monitor the Specific DTC info for this DTC. Does the scan tool indicate that this DTC failed this ignition?	Go to Step 2	System OK