Diagnostic Aids

WARNING: This page is about a different car, the 2007 Isuzu i-370, 2007 GMC Canyon, and 2007 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP canister vent solenoid valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.
An EVAP canister, vent hose or vent solenoid valve that has restricted flow may cause this DTC to set. Using purge solenoid valve command with a scan tool will allow vacuum to be applied to the system instead of pressure. With the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, vacuum should not increase to more than 9 inches H2O.
For intermittent conditions, refer to Intermittent Conditions .

DTC P0446

Step	Action	Values	Yes	No
Schematic Reference: Evaporative Emissions Hose Routing Diagram
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Inspect the evaporative emission (EVAP) system for the following conditions: A damaged EVAP canister vent solenoid valve-Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . A pinched EVAP vent hose A damaged EVAP canister-Refer to Evaporative Emission Canister Replacement . Did you find and correct the condition?	-	Go to Step 12	Go to Step 3
3	Turn OFF the ignition. Disconnect the purge pipe at the EVAP service port. Turn ON the ignition, with the engine OFF. Is the fuel tank pressure sensor parameter within the specified range?	-1 to +1 in H2O	Go to Step 4	Go to Step 8
4	IMPORTANT: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results. Turn OFF the ignition. Connect the EVAP purge line. Connect the J 41413-200 Evaporative Emissions System Tester (EEST) power supply clips to a known good 12-volt source. Install the GE-41415-50 Interrupted Thread Fuel Tank Cap Adapter to the fuel fill pipe. Connect the fuel fill cap to the GE-41415-50 . Connect the J 41413-200 nitrogen/smoke supply hose to the GE-41415-50 . Turn ON the ignition, with the engine OFF Command the EVAP canister vent solenoid valve closed with a scan tool. Turn the nitrogen/smoke valve on the J 41413-200 control panel to NITROGEN. Use the remote switch to pressurize the EVAP system to the first specified value. Observe the fuel tank pressure sensor in H2O with a scan tool. Command the EVAP canister vent solenoid valve open with a scan tool. Is the fuel tank pressure sensor parameter less than the second specified value?	5 in H2O 1 in H2O	Go to Diagnostic Aids	Go to Step 5
5	Disconnect the EVAP vent hose from the EVAP canister vent solenoid valve. Is the fuel tank pressure sensor parameter less than the specified value?	1 in H2O	Go to Step 10	Go to Step 6
6	Disconnect the EVAP vent hose from the EVAP canister. Is the fuel tank pressure sensor parameter less than the specified value?	1 in H2O	Go to Step 7	Go to Step 11
7	Repair the pinched or restricted EVAP vent hose. Did you complete the repair?	-	Go to Step 12	-
8	Test for poor connections at the harness connector of the fuel tank pressure (FTP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	-	Go to Step 12	Go to Step 9
9	Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Did you complete the replacement?	-	Go to Step 12	-
10	Replace the EVAP vent solenoid valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Did you complete the replacement?	-	Go to Step 12	-
11	Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement . Did you complete the replacement?	-	Go to Step 12	-
12	Turn OFF the ignition. Disconnect the purge line from the EVAP canister purge solenoid valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Turn ON the ignition, with the engine OFF. Is the fuel tank pressure sensor parameter within the specified range?	-1 to +1 in H2O	Go to Step 13	Go to Step 2
13	IMPORTANT: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results. Turn OFF the ignition. Reconnect all disconnected components. Connect the J 41413-200 to the fuel fill pipe. Turn ON the ignition, with the engine OFF Command the EVAP canister vent solenoid valve closed with a scan tool. Turn the nitrogen/smoke valve on the J 41413-200 control panel to NITROGEN. Use the remote switch to pressurize the EVAP system to the first specified value. Observe the fuel tank pressure sensor in H2O with a scan tool. Command the EVAP canister vent solenoid valve open with a scan tool. Is the fuel tank pressure sensor parameter less than the second specified value?	5 in H2O 1 in H2O	Go to Step 14	Go to Step 2
14	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	System OK