Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. 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 P0621

Step	Action	Value	Yes	No
Schematic Reference: Starting and Charging Schematics Connector End View Reference: 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. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Using the scan tool, observe the Specific DTC Information for DTC P0621 until the test runs. Does the scan tool indicate that DTC P0621 has passed this ignition cycle?	-	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Install a scan tool. Start the engine. Turn OFF all accessories, including headlamps. With a scan tool, observe the Ignition 1 Signal parameter in the PCM data list. Does the scan tool indicate that the voltage is above the specified value?	13.0 V	Go to Step 6	Go to Step 4
4	With the scan tool command the GEN L-Terminal ON and OFF. Does the scan tool indicate that the voltage level changes with each command?	-	Go to Step 10	Go to Step 5
5	Turn OFF the ignition. Disconnect the generator harness connector. Start the engine. Measure the voltage between the generator turn on signal circuit and a known good ground. With the scan tool command the GEN L-Terminal ON and OFF. Is the voltage less than the first value with the generator OFF and greater than the second value with the generator ON?	1.5 V 4.6 V	Go to Step 10	Go to Step 9
6	Turn OFF the ignition. Disconnect the generator harness connector. Start the engine. Measure the voltage between the generator sense circuit and a known good ground. Is the voltage equal to the specified value?	B+	Go to Step 7	Go to Step 8
7	Test the battery positive voltage circuit of the generator 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 13	Go to Step 10
8	Test the generator sense 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 13	Go to Step 10
9	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 13	Go to Step 11
10	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 13	Go to Charging System Test
11	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 13	Go to Step 12
12	IMPORTANT: The replacement PCM must be programmed Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 3.8L (L26 and L32)Did you complete the replacement?	-	Go to Step 13	-
13	Review and record the scan tool Fail Records data. Use the scan tool in order to clear the DTC. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Using the scan tool, observe the Specific DTC Information for DTC P0621 until the test runs. Does the scan tool indicate that DTC P0621 failed this ignition?	-	Go to Step 3	System OK