Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.

The ECM clears the DIC message when the condition no longer exists.
A scan tool can clear the DIC/DTC.
The ECM clears the DTC from ECM history if the vehicle completes 40 warm-up cycles without a non-emission-related diagnostic fault occurring.
The ECM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the ECM.

DTC P0851

Step	Action	Value(s)	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Install a scan tool. Turn ON the ignition with the engine OFF. IMPORTANT: Record the Failure Records before clearing the DTCs. Using the Clear Info function erases the Failure Records. Using the Clear Info function erases stored DTCs in both the ECM and TCM. Record the DTC Failure Records. Clear the DTC. Did you record TCM Failure Records for DTC P1820, P1822, P1823, P1825, P1826 or P1915?	-	Go to Diagnostic Trouble Code (DTC) List/Type	Go to Step 3
3	Turn ON the ignition with the engine OFF. Select Engine Data on the scan tool. Monitor the PNP Switch display on the scan tool. Shift the transmission from Park to Drive. Does the PNP Switch display Park/Neutral?	-	Go to Step 4	Go to Testing for Intermittent Conditions and Poor Connections
4	Disconnect the automatic transmission inline 20-way connector. Does the PNP Switch display Park/Neutral?	-	Go to Step 6	Go to Step 5
5	Test the PNP Switch signal circuit for a short to ground between the automatic transmission inline 20-way connector and transmission internal mode switch. Refer to Testing for Short to Ground . Did you find the condition?	-	Go to Step 7	Go to Step 8
6	Test the PNP Switch signal circuit for a short to ground between the automatic transmission inline 20-way connector and the ECM. Refer to Testing for Short to Ground . Did you find and correct the condition?	-	Go to Step 10	Go to Step 9
7	IMPORTANT: The automatic transmission wiring harness consists of 2 separate harnesses, the Automatic Transmission Wiring Harness Assembly and the Automatic Transmission Wiring Extension Harness Assembly. In order to avoid the unnecessary replacement of parts, determine which harness contains the fault and replace only that harness. Replace the automatic transmission wiring harness.Refer to Input Speed Sensor and Wiring Harness Removal in the 4T80-E section of the Transmission Unit Repair Manual.Did you complete the replacement?	-	Go to Step 10	-
8	Replace the transmission internal mode switch. Refer to Lower Control Valve Body Assembly Disassemble in the 4T80-E section of the Transmission Unit Repair Manual. Is the action complete?	-	Go to Step 10	-
9	Replace the ECM. Refer to Control Module References for replacement, set-up and programming. Is the action complete?	-	Go to Step 10	-
10	Perform the following procedure to verify the repair: Select DTC. Select Clear DTC Information. Turn OFF the ignition for at least 30 seconds. Start the engine. Select Specific DTC. Enter DTC P0851. Has the test run and passed?	-	Go to Step 11	Go to Step 2
11	With the 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 (DTC) List - Vehicle	System OK