For 1990-2009 cars
EGR Valve and EVAP Controls
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The evaporative emission (EVAP) control system prevents the emission of fuel vapors. The fuel vapor generated in the fuel tank while driving or idling the engine, pass through the fuel tank pressure control valve and enter the EVAP canister. The fuel vapors are stored in the charcoal element of the EVAP canister. The powertrain control module (PCM) operates the EVAP canister purge valve, allowing the fuel vapors to be drawn into the intake manifold from the EVAP canister. The DTC P0443 diagnostic monitors the EVAP canister purge valve control circuit voltage.

### 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 PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns off after 3 consecutively passing trips without a fault present.

• | A history DTC clears after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool Clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

If DTCs 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 DTC P0443 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0443 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. 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. The 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.

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 electrical circuit of the EVAP canister purge valve . Inspect the wiring harness and the components for any of the following conditions:

• | Any backed-out terminals

• | Any improper mating of terminals

• | Any broken electrical connector locks

• | Any improperly formed or damaged terminals

• | Any faulty terminal-to-wire connections

• | Any physical damage to the wiring harness

• | A broken wire inside the insulation

• | Any corrosion of the electrical connections, the splices, or the terminals

If a DTC P0443 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the 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 Powertrain OBD System Check 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 determines if the condition that caused DTC P0443 to set still exists.

3. This step checks the control circuit of the EVAP canister purge valve . The duty cycle control of the EVAP canister purge valve 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. The output controls can be found on the scan tool under Special Functions.

4. This step determines if the malfunction that caused DTC P0443 to set 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 the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0443 appears in the Not Ran Since Code Cleared list, the P0443 diagnostic has not yet run. When 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. The 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
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
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 electrical connector from the EVAP canister purge valve .
3. Measure the resistance of the EVAP canister purge valve using a digital multimeter (DMM).

Is the resistance within the specified range?

28 - 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 purge valve electrical connector with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 7

5 |

1. Connect the electrical connector to the EVAP canister purge valve .
2. Backprobe the purge valve control circuit with a test lamp connected to B+.
3. Command the 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 at the 100 percent duty cycle?

--

Go to Step 8

Go to Step 6

6 |

1. Check for an open or a short in the 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 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 10 | --
10 |

1. Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditions that set the DTC or until the P0443 diagnostic test has run.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to Diagnostic Trouble Code (DTC) List

System OK