For 1990-2009 cars

### Circuit Description

The DTC P0443 EVAP System Incorrect Purge Flow diagnostic monitors the control circuit voltage of the EVAP canister purge valve. Ignition voltage is supplied directly to the EVAP canister purge valve solenoid. The powertrain control module (PCM) supplies a ground path to the solenoid control circuit using an internal solid state device called a driver. Each driver has a fault line that is monitored by the PCM. When the PCM commands the solenoid ON, the voltage on the control circuit should be near zero or low. When the PCM commands the solenoid OFF, the voltage on the control circuit should be near battery voltage or high. If the fault detection circuit senses a voltage other than what is expected, this DTC will set.

The PCM will monitor the solenoid control circuit for the following conditions:

• | A short to ground

• | A short to voltage

• | An open circuit

• | An open solenoid

• | An internally shorted or excessively low resistance solenoid coil

### Condition for Running the DTC

The ignition is ON, or the engine is running.

### Conditions for Setting the DTC

• | The PCM does not detect the expected voltage on the EVAP canister purge valve circuit.

• | The above condition is present for 2 seconds.

### Action Taken When the DTC Sets

• | The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL will turn OFF after three consecutive drive cycles without a fault present.

• | A DTC will clear after 40 consecutive warm-up cycles without a fault.

• | The DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

### Diagnostic Aids

If a DTC P0440 and P0443 are both set, the most likely cause is an inoperable EVAP canister purge valve. Inspect the EVAP canister purge valve carefully for faulty connections and erratic operation.

If a DTC P0443 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Evaporative Emission System Set .

Test the operation of the EVAP canister purge valve. Refer to Evaporative Emission Control System Diagnosis .

An intermittent malfunction may be caused by a fault in the EVAP canister purge valve electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If you duplicate a DTC P0443, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

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

1. The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks whether the condition that caused the DTC P0443 to set still exists.

3. This step checks the EVAP canister purge valve control circuit. The EVAP canister purge valve duty cycle control is disabled by the PCM until the engine has reached a normal operating temperature of at least 80°C (176°F), there is no RPM indicated, and there are no DTCs set. Output controls can be found on the scan tool under Special Functions.

4. This step checks whether the malfunction that caused the DTC P0443 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool Clear DTC Information function, the DTC P0443 diagnostic can be monitored on the scan tool under Not Ran Since Code Cleared. If a DTC P0443 appears in the Not Ran Since Code Cleared list, the P0443 diagnostic has not yet run. When the DTC P0443 does not appear in the Not Ran Since Code Cleared list, the P0443 diagnostic has run. If the MIL is NOT ILLUMINATED and there is no PENDING DTC Status in DTC Information, the P0443 diagnostic has passed. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT or PENDING status, in order to determine the outcome of the diagnostic test involved.

Step | Action | Value(s) | 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. Perform the scan tool Clear DTC Information function.
2. Start the engine.
3. Run the engine for 1 minute and check for DTCs.

Is there a CURRENT or PENDING DTC P0443 set?

--

Go to Step 3

Go to Diagnostic Aids

3 |

1. Turn OFF the ignition.
2. Disconnect the EVAP canister purge valve electrical connector.
3. Measure the resistance of the EVAP canister purge valve using a DMM.

Is the resistance within the specified value?

28 to 36 ohms at 20°C (68°F)

Go to Step 4

Go to Step 8

4 |

1. Turn ON the ignition, leaving the engine OFF.
2. Probe the ignition positive voltage circuit at the EVAP canister purge valve electrical connector with a test lamp connected to ground.

Did the test lamp illuminate?

--

Go to Step 5

Go to Step 7

5 |

1. Connect the EVAP canister purge valve electrical connector.
2. Backprobe the EVAP canister purge valve control circuit with a test lamp connected to B+.
3. Command the EVAP canister purge valve ON using a scan tool.
4. Adjust the duty cycle from 0 to 100 percent while observing the test lamp.

Does the test lamp flash and then illuminate steadily when you reach 100 percent duty cycle?

--

Go to Step 8

Go to Step 6

6 |

1. Check for an open or a short in the EVAP canister purge valve control circuit.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 10

Go to Step 9

7 |

1. Check for an open in the ignition positive voltage circuit.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 10

--

8 | Replace the EVAP canister purge valve. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 10 | --
9 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the replacement complete? | -- | Go to Step 10 | --
10 |

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 11

Go to Step 2

11 | 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