The EVAP Vent valve is supplied power via the Engine Controls Power Relay (Switched B+). The Engine Control Module (ECM) controls the valve by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component on, the voltage of the control circuit should be low (near 0 volts). When the ECM is commanding the control circuit to a component off, the voltage potential of the circuit should be high (near battery voltage). If the fault detection circuit senses a voltage other than what is expected, this DTC will set.
The ECM will monitor the EVAP Vent valve circuit for the following:
| • | A short to ground |
| • | A short to voltage |
| • | An open circuit |
| • | An internally shorted or excessively low resistance EVAP Vent valve circuit |
When the ECM detects any of the above malfunctions, this DTC will set and the affected driver will be disabled. The ECM will continue to test the circuit and if the fault goes away, the driver will be reactivated.
Conditions for Running the DTC
| • | The ignition voltage is between 9.0 and 17.0 volts. |
| • | The engine speed is greater than 80 RPM. |
Conditions for Setting the DTC
A short to ground, an open circuit, or a short to battery voltage is detected on the control circuit.
Action Taken When the DTC Sets
The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes. |
| • | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic. |
| • | The ECM battery voltage is interrupted. |
| • | The scan tool clears the MIL/DTC. |
Diagnostic Aids
| • | Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals. |
| • | If an intermittent circuit problem is suspected, check for the following conditions: |
| - | Misrouted harness. Inspect the harness in order to ensure that the harness is not routed too close to any high voltage wires such as spark plug leads, or too close to any high current devices such as the alternator, the motors, the solenoids, etc. |
| - | Damaged harness. Inspect the wiring harness for any damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault. |
Refer to Symptoms for the Intermittents.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table:
-
Listen for an audible click when the valve operates. Repeat the commands as necessary.
-
This check can detect a partially shorted coil which would cause excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm the coil may open (amps drop to 0), or short (goes above 0.75 amp).
-
If no trouble is found in the control circuit or the connection at the ECM, the ECM may be damaged, however, this is an extremely unlikely failure.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | ||
2 |
Does the valve turn on and off with each command? | -- | ||
3 |
Does the current draw a measure within the range shown? | 0.1 to 0.75 A | Refer to Diagnostic Aids | |
4 |
The DVM should display an infinite resistance. Does the DVM display an infinite resistance? | -- | ||
5 |
Does the test light turn on and off with each command? | -- | ||
6 | Probe the Switched B+ circuit in the valve harness connector with the test light connected to ground. The test light should illuminate. Does the test light illuminate? | -- | ||
7 |
Does the valve operate? | -- | ||
8 | Check connections at the valve. Was a problem found and corrected? | -- | ||
9 | Repair the valve control circuit. Is the action complete? | -- | -- | |
10 | Repair the Switched B+ circuit to the valve. Is the action complete? | -- | -- | |
11 | Replace the valve. Is the action complete? | -- | -- | |
12 | Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||
13 |
Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | -- | |
14 |
Is this DTC set? | -- | ||
15 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK |
