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 7.5 volts and 15.0 volts. |
| • | The engine speed is greater than 40 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
Notice: Using the J 35616-A Connector Test Adapter Kit will prevent damage to the harness connector terminals.
| • | Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. |
| • | If an intermittent circuit problem is suspected, check for a damaged harness. Inspect the wiring harness thoroughly. 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 locate the fault. |
Refer to Symptoms for the Intermittents.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Listen for an audible click when the valve operates. Repeat the commands as necessary.
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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, the amps drop to 0, or short, go to above 0.75 amp).
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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 | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | Go to Step 2 | |||||
Does the valve turn ON and OFF with each command? | -- | Go to Step 3 | Go to Step 5 | |||||
Does the current draw measure within the range shown? | 100 to 750 mA | Go to Diagnostic Aids | Go to Step 4 | |||||
4 |
The DMM should display an infinite resistance. Does the DMM display an infinite resistance? | -- | Go to Step 11 | Go to Step 12 | ||||
5 |
Does the test lamp turn ON and OFF with each command? | -- | Go to Step 11 | Go to Step 6 | ||||
6 | Is the test lamp continuosly illuminated? | -- | Go to Step 8 | Go to Step 7 | ||||
7 | Probe the Switched B+ circuit in the valve harness connector with the test lamp connected to ground. The test lamp should illuminate. Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 15 | ||||
8 |
Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 17 | ||||
9 | Connect the J 34142-B test lamp between ground and the valve control circuit terminal. The test lamp should not illuminate. Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 10 | ||||
10 |
Does the DMM indicate circuit continuity? | -- | Go to Step 17 | Go to Step 13 | ||||
11 | Check connections at the EVAP tank solenoid (vent) valve. Did you find and correct a problem? | -- | Go to Step 19 | Go to Step 16 | ||||
12 | Repair the shorted to ground EVAP tank solenoid control circuit. Is the action complete? | -- | Go to Step 19 | -- | ||||
13 | Repair the open EVAP tank solenoid control circuit. Is the action complete? | -- | Go to Step 19 | -- | ||||
14 | Repair the EVAP tank solenoid control circuit shorted to B+. Is the action complete? | -- | Go to Step 19 | -- | ||||
15 | Repair the open Switched B+ circuit to the EVAP tank solenoid valve. Is the action complete? | -- | Go to Step 19 | -- | ||||
16 | Replace the EVAP Tank Solenoid (vent) valve. Is the action complete? | -- | Go to Step 19 | -- | ||||
17 | Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Wiring Repairs in Wiring Systems. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Did you find and correct a problem? | -- | Go to Step 19 | Go to Step 18 | ||||
|
Important:
Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 19 | -- | |||||
19 |
Does the scan tool indicate that the diagnostic Passed? | -- | Go to Step 20 | Go to Step 2 | ||||
20 | Does the scan tool display any additional, undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
