GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Sonoma Pickup - 4WD 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 DTC P0443

Circuit Description

An ignition voltage is supplied directly to the evaporative emission (EVAP) purge valve. The EVAP purge valve is pulse width modulated (PWM). The control module controls the EVAP purge valve ON time by grounding the control circuit via an internal switch called a driver. The scan tool displays the amount of ON time as a percentage. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, DTC P0443 sets.

Conditions for Running the DTC
    • The engine speed is more than 400 RPM.
    • The system voltage is between 6-18 volts.

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

Action Taken When the DTC Sets
    • The control module will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test ran and failed.
    • The control module will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

Conditions for Clearing the MIL/DTC
    • The control module will turn OFF the MIL during the third consecutive trip in which the diagnostic ran and passed.
    • The History DTC will clear after 40 consecutive warm-up cycles without a malfunction.
    • The DTC can be cleared with a scan tool.

Test Description

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

  1. This step tests if the concern is active.

  2. This step verifies that the control module is providing ground to the EVAP purge valve.

    3.

  3. This step tests if a ground is constantly being applied to the EVAP purge valve.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Start and idle the engine.
  2. With the scan tool, command the vent valve ON, closed.
  3. Monitor the FTP sensor value with the scan tool.
  4. Command the purge valve to 50 percent.

Does the FTP value on the scan tool change?

Go to Step 3

Go to Step 4

3
  1. Review the Freeze Frame/Failure Records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

Go to Step 4

Go to Intermittent Conditions

4
  1. Turn OFF the ignition.
  2. Disconnect the EVAP purge valve harness connector. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition voltage circuit at the EVAP purge valve harness connector with a test lamp connected to a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 11

5

  1. Connect a test lamp between the control circuit and the ignition voltage circuit of the EVAP purge valve harness connector.
  2. With a scan tool, command the EVAP purge valve to 0 percent.

Is the test lamp illuminated?

Go to Step 9

Go to Step 6

6

With a scan tool, command the EVAP purge valve to 50 percent.

Does the test lamp illuminate or pulse when the EVAP purge valve is commanded to 50 percent?

Go to Step 8

Go to Step 7

7

Test the control circuit of the EVAP purge valve for an open or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 10

8

Test the control circuit of the EVAP purge valve for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 13

9

Inspect for poor connections at the harness connector of the EVAP purge 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 14

Go to Step 12

10

Inspect for poor connections at the harness connector of the control module. 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 14

Go to Step 13

11
  1. Repair the ignition voltage circuit of the EVAP purge valve for an open or a short to ground.
  2. Replace the fuse if necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 14

--

12

Replace the EVAP purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement .

Did you complete the replacement?

Go to Step 14

--

13

Replace the control module. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 14

--

14
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 15

Go to Step 2

15

With a scan tool, observe the stored information, Capture Info.

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

Go to Diagnostic Trouble Code (DTC) List

System OK