The evaporative emission (EVAP) vent valve is supplied switched battery power via the engine controls power relay. 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 diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
| • | The ignition voltage is 7.5-15.0 volts. |
| • | The engine speed is more 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 control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | Use the J 35616 Connector Test Adapter Kit 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 Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Refer to Intermittent Conditions 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 | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||
Does the valve turn ON and OFF? | -- | Go to Step 3 | Go to Step 5 | |||||
Is the amperage within the specified range? | 100-750 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? | -- | Go to Step 11 | Go to Step 6 | ||||
6 | Is the test lamp continuously 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 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 vent solenoid valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 | ||||
12 | Repair the shorted to ground EVAP vent solenoid control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 19 | -- | ||||
13 | Repair the open EVAP vent solenoid control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 19 | -- | ||||
14 | Repair the EVAP vent solenoid control circuit shorted to B+. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 19 | -- | ||||
15 | Repair the open switched B+ circuit to the EVAP vent solenoid valve. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 19 | -- | ||||
16 | Replace the EVAP vent valve. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||
17 | Test for a poor connection or poor terminal tension at the ECM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 | ||||
|
Important:
Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the action? | -- | Go to Step 19 | -- | |||||
19 |
Does the DTC run and pass? | -- | Go to Step 20 | Go to Step 2 | ||||
20 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
