Diagnostic Trouble Code (DTC) P0444

EVAP Purge Control Circuit No Signal

 

 

Features of the Circuit


The evaporative emission (EVAP) system comprises the following components:

  • Fuel tank.
  • EVAP vent solenoid.
  • Fuel pipes and hoses.
  • Fuel vapor lines.
  • Fuel cap.
  • EVAP canister.
  • Purge lines.
  • EVAP canister purge valve.
  • EVAP service port.

Further Details:

  • The evaporative emission system is probed by applying vacuum to the EVAP system and monitoring for a vacuum decay.
  •  The engine control module (ECM) monitors the vacuum level through the fuel tank pressure sensor signal.
  • The EVAP canister purge valve and the EVAP vent solenoid are turned on at the nick of time, allowing the engine to suck up a small vacuum on the entire EVAP system.
  •  After the requisite vacuum level has been obtained, the EVAP canister purge valve is switched OFF, locking the system entirely.
  •  If sufficient vacuum level cannot be derived, a large leak is indicated. This can be caused by the following conditions :
  1. Missing or faulty fuel cap.
  2. Disconnected or flawed fuel tank pressure sensor.
  3. Disconnected, damaged, pinched, or blocked EVAP purge line.
  4. Disconnected or erroneous EVAP canister purge valve.
  5. Disconnected or faulty EVAP vent solenoid.
  6. Open ignition feed circuit to the EVAP vent or purge solenoid.
  7. Damaged EVAP canister.
  8. Leaking fuel sensor assembly O-ring.
  9. Leaking fuel tank or fuel filler beck.

Any of the above conditions can set DTC P0444.

  • The test is aborted if the tank vacuum is < 10 in H20 for 15 seconds and the manifold vacuum integral is > 49512 (proportional to purge mass from the tank).

 

Time for setting the DTC

Task boosted after DTC sets

When will DTC clear?

1) When the canister purge solenoid circuit is in an open condition.

1) The Malfunction Indicator Lamp (MIL) will glow after three successive trips with a fail.

1) The MIL will turn off after four consecutive ignition cycles in which the diagnostic runs without a fault.

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2) The ECM will begin to store conditions which were present when the DTC failed.

 

2) Disconnecting the ECM battery feed for 10 seconds

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3) This information will be recorded in the Freeze Frame buffering Failure Records.

 

3) The scan tool can be used to remove all existing DTCs.

 

 

4) A history DTC will be stored.

 

4) A history DTC will clear after 40 consecutive warm-up cycles without a fault.

       

Diagnostic Assistance

Although  this DTC is considered a kind  of   type. A diagnostic, it acts like a type B diagnostic under certain conditions. Whenever this diagnostic indicates the system has passed, or if the battery is disconnected, the diagnostic must fail twice before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.

 Under this circumstance check for the following conditions :

  • Absent or tampered fuel cap.
  • Absent or tampered O-rings at fuel vapor and EVAP purge line canister fittings.
  • Cracked or punctured EVAP canister.
  • Damaged source vacuum line, EVAP purge line, EVAP vent hose or fuel tank vapor line.
  • Poor connection at the ECM. Inspect the harness connectors for the following conditions.
  • Backed-out terminals.
  • Improper mating.
  • Broken locks.
  • Improperly formed.
  • Damaged terminals.
  • Poor terminal-to-wire connection.
  • Damaged harness. Examine a) the wiring harness to the EVAP vent solenoid, b) EVAP canister purge valve and c) the fuel tank pressure sensor to ensure whether an intermittent open or short circuit prevails.
  • Kinked, pinched or plugged vacuum source, EVAP purge, or fuel tank vapor line. Ensure that the lines are not restricted.

                                             

                                                      STEPS TO JUDGE A DTC

                                       DTC P0444 - EVAP Purge Control Circuit No Signal


 Step

Task

Positive

Negative

1

Perform EOBD System Check.

Task Done?

Look up Step 2

Look up "On-Board Diagnostic System Check"

2

  1. De-link the evaporative emission (EVAP) canister purge valve connector.
  2. Link up a test light between the EVAP canister purge valve connector terminal 2 and battery positive.

Can you see the test light ON?

Look up Step 3

Look up Step 5

3

  1. Dissociate the ECM connector.
  2. Attach a test light between the ECM connector terminal 65 and ground.

Can you see the test light ON?

Look up Step 4

Look up Step 6

4

  1. Repair the line break in the wire between the EVAP canister purge valve connector 1 and the ECM connector terminal 65.
  2. Clear any Diagnostic Trouble Codes (DTCs) from the ECM.
  3. Perform the diagnostic system check.

 Test Done?

The system of your vehicle is fine

-

5

  1. Repair the line break in the wire between the EVAP canister purge valve connector 2 and the main relay connector terminal 87.
  2. Clear any Diagnostic Trouble Codes (DTCs) from the ECM.
  3. Perform the diagnostic system check.

 Test Undertaken?

The system of your vehicle is fine

-

6

  1. Change the ECM.
  2. Carry out the diagnostic system check.

 Task Accomplished?

Look up Step 7

-

7

                    1) Unset all DTCs taking a Scan Tool.

2)       Start the engine and idle at normal operating temperature.

3)       Operate the vehicle within the specified conditions for setting this DTC

Do you see the scan tool confirming that this diagnostic has been operated and the test passed?

Look up Step 8

Look up Step 2

8

 

Check if any additional DTCs are set.

Are any DTCs displayed that have not been diagnosed?

Look up Applicable DTC table

The system of your vehicle is fine