GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The evaporative emission (EVAP) solenoid valve is pulse width modulated (PWM). The powertrain control module (PCM) controls the EVAP canister purge solenoid valve duty cycle by controlling the amount of purge valve solenoid ON time. The scan tool displays the amount of ON time in percentage. This value is the amount of available vacuum that is applied to the EVAP system.

An ignition voltage is supplied directly to the EVAP canister purge valve. The PCM controls the solenoid by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. Each driver has a fault line which the PCM monitors. The voltage of the control circuit should be low, near 0 volts, when the PCM commands a component ON. The voltage potential of the circuit should be high, near the battery voltage, when the PCM commands the control circuit to a component OFF. If the fault detection circuit senses a voltage other than what the PCM expects, the fault line status changes causing the diagnostic trouble code (DTC) to set.

Conditions for Running the DTC

    • The engine speed is more than 400 RPM.
    • The ignition voltage is between 6-18.0 volts.

Conditions for Setting the DTC

    • The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
    • The conditions are present for a minimum of 5 seconds.

Action Taken When the DTC Sets

    • The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

    • The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Use a scan tool in order to clear the MIL and the DTC.

Diagnostic Aids

Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

Using Freeze Frame/Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid in determining how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that you observed. This will isolate when the DTC failed.

For an intermittent, refer to Symptoms - Engine Controls .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests the ON and OFF states of the solenoid.

  2. 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, amps go above 0.75.

  3. If no trouble is found in the control circuit or the connection at the PCM, the PCM may be faulty, 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?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Turn ON the ignition, with the engine OFF.
  2. Important: Listen for an audible click when the solenoid operates. Be sure that both the ON and the OFF states are commanded. Repeat the commands as necessary.

  3. Command the solenoid ON and OFF using the scan tool.

Does the solenoid turn ON and OFF when commanded?

--

Go to Step 3

Go to Step 5

3

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C2 located on the opposite side of the manufacturers logo. Refer to Powertrain Control Module Replacement .
  3. Install 5-amp fused jumper wire to the control circuit at the PCM harness connector.
  4. Turn ON the ignition, with the engine OFF.
  5. Measure the current from the solenoid control circuit in the PCM harness connector to ground for 2 minutes using the DMM on the 40-amp scale.

Important: Replace the solenoid if the amperage goes to 0 during the current draw test.

Does the current draw measure less than the specified value shown?

0.75 A

Go to Diagnostic Aids

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the solenoid.
  3. Measure the resistance from the solenoid control circuit in the PCM harness connector to ground using the DMM .

Does the DMM display infinite (OL) resistance?

--

Go to Step 12

Go to Step 10

5

  1. Turn OFF the ignition.
  2. Disconnect the solenoid.
  3. Connect the test lamp between the terminals in the solenoid harness connector.
  4. Turn ON the ignition, with the engine OFF.
  5. Command the solenoid ON and OFF using the scan tool.

Does the test lamp turn ON and OFF when commanded?

--

Go to Step 8

Go to Step 6

6

With the test lamp connected to ground, probe the ignition feed circuit in the solenoid harness connector. Refer to Probing Electrical Connectors in Wiring Systems.

Is the test lamp illuminated?

--

Go to Step 7

Go to Step 11

7

  1. Turn OFF the ignition.
  2. Reconnect the solenoid.
  3. Disconnect the PCM connector C2 located on the opposite side of the manufacturers logo. Refer to Powertrain Control Module Replacement .
  4. Turn ON the ignition, with the engine OFF.
  5. With a fused jumper wire connected to ground, momentarily probe the solenoid control circuit in the PCM harness connector. Refer to Using Fused Jumper Wires in Wiring Systems.

Is there an audible click from the solenoid when the circuit is grounded and when the circuit is opened?

--

Go to Step 9

Go to Step 10

8

  1. Inspect the connections at the solenoid. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If you find a poor connection, repair the terminal as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

9

  1. Inspect the connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If you find a poor connection, repair the terminal as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

10

Repair the faulty solenoid control circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 14

--

11

Repair the faulty solenoid ignition feed circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 14

--

12

Replace the solenoid. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

Is the action complete?

--

Go to Step 14

--

13

Important: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement .

Is the action complete?

--

Go to Step 14

--

14

  1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
  2. Idle the engine at the normal operating temperature.
  3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 15

Go to Step 2

15

Select the Capture Info option and the Review Info option using the scan tool.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to the applicable DTC table

System OK