Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The ECM turns OFF the MIL during the third consecutive trip in which the diagnostic runs and passes.
The ECM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the ECM.
The ECM clears the DTC from ECM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring.
A scan tool can clear the MIL/DTC.

DTC P0502

Step	Action	Value(s)	Yes	No
1	Did you perform the Diagnostic System Check?	-	Go to Step 2	Go to DIAGNOSTIC SYSTEM CHECK -- ENGINE CONTROLS
2	Install a scan tool. Turn ON the ignition with the engine OFF. IMPORTANT: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Record the DTC Freeze Frame and Failure Records. Clear the DTCs. NOTE: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel. Raise the drive wheels. Start and idle the engine. Place the transmission in 1st gear. Monitor Vehicle Speed on the scan tool. With the drive wheels rotating, increase and decrease the throttle position. Does the scan tool indicate Vehicle Speed increasing when wheel speed increases?	-	Refer to INTERMITTENTS	Go to Step 3
3	Turn OFF the ignition. Disconnect the Vehicle Speed Sensor (VSS). Turn ON the ignition with the engine OFF. Using the DMM, measure the voltage of ignition 1 voltage circuit (CKT 239) of the VSS to ground. Does the voltage measure near the specified value?	B+	Go to Step 4	Go to Step 9
4	Measure the voltage from the ignition 1 voltage circuit (CKT 239) of the VSS to the VSS ground circuit (CKT 451). Does the voltage measure near the specified value?	B+	Go to Step 5	Go to Step 12
5	Using the J 35616 GM terminal test kit, connect a jumper between the ignition 1 circuit and the VSS. Connect another jumper between the VSS ground circuit and the VSS. Connect the DMM between terminal 1 of the VSS and ground. Turn ON the ignition, with the engine OFF. Select AC volts on the DMM. Place transmission in neutral. Rotate the rear wheels by hand while observing the DMM AC volts. Does the DMM display AC volts above the specified value?	.15 V	Go to Step 6	Go to Step 16
6	Turn OFF the ignition. Disconnect the ECM. Using the DMM, measure the resistance of the VSS high signal circuit (CKT 821) between terminal C1-18 of the ECM and terminal 1 of the VSS. Does the resistance measure less than the specified value?	5 Ω	Go to Step 7	Go to Step 13
7	Using the DMM, measure the resistance between the VSS high signal circuit (CKT 821) and ground. Is the resistance less than the specified value?	50 kΩ	Go to Step 8	Go to Step 14
8	Using a test lamp connected to the ground, probe the VSS high signal circuit (CKT 821). Does the test lamp illuminate?	-	Go to Step 15	Go to Step 18
9	Inspect the BACKUP fuse for an open. Refer to Circuit Protection - Fuses in Wiring Systems. Replace the fuse if necessary. Was the fuse open?	-	Go to Step 10	Go to Step 11
10	IMPORTANT: The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Power Distribution Schematics in Wiring Systems for complete circuit distribution. Test the ignition 1 voltage circuit (CKT 239) of the VSS for a short to ground. Refer to Testing for Short to Ground in Wiring Systems.Did you find and correct the condition?	-	Go to Step 19	-
11	Test for an open or high resistance in the ignition 1 voltage circuit (CKT 239) of the VSS. Refer to Testing for Continuity in Wiring Systems. Did you find and correct the condition?	-	Go to Step 19	-
12	Repair the open in the VSS ground circuit (CKT 451). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	-	Go to Step 19	-
13	Repair the open in the VSS high signal circuit (CKT 821). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	-	Go to Step 19	-
14	Repair the short to ground in the VSS high signal circuit (CKT 821). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	-	Go to Step 19	-
15	Repair the short to voltage on the VSS high signal circuit (CKT 821). Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	-	Go to Step 19	-
16	Remove the VSS sensor. Refer to Vehicle Speed Sensor (VSS) Replacement . Inspect the VSS and the transmission for the following: Incorrect VSS VSS damage Excessive VSS to rotor gap Incorrect VSS rotor alignment VSS rotor damage Loose VSS Repair any of the above conditions. Did you find and correct the condition?	-	Go to Step 19	Go to Step 17
17	Replace the VSS. Refer to Vehicle Speed Sensor (VSS) Replacement . Did you complete the repair?	-	Go to Step 19	-
18	Replace the ECM. Refer to ENGINE CONTROL MODULE . Did you complete the repair?	-	Go to Step 19	-
19	In order to verify your repair, perform the following procedure: Select DTC. Select Clear Info. Drive the vehicle. Ensure the vehicle speed is greater than 5 km/h (3 mph) for at least 3 seconds. Select specific DTC. Enter DTC P0502. Has the test run and passed?	-	Go to Step 20	Go to Step 2
20	With a scan tool observe the stored information, capture info and DTC Info. Does the scan tool display any DTCs that you have not diagnosed?	-	Go to DIAGNOSTIC TROUBLE CODE DEFINITIONS	System OK