P1443 - Very Small Or No Purge Flow Condition A fuel tank pressure change greater than a minus (-) 7 inches of H 2 O in 30 seconds has occurred with purge (fuel vapor) flow less than 0.02 pounds per minute.
- Blocked fuel vapor hose between EVAP canister purge valve and FTP sensor.
- Blocked fuel vapor hose between EVAP canister purge valve and engine intake manifold.
- Blocked vacuum hose between EVAP canister purge valve-solenoid and engine intake manifold.
- EVAP canister purge valve stuck closed (mechanically).
Check for blockages between the fuel tank, EVAP canister purge valve and engine intake manifold. Check obstructions in the EVAP canister purge valve diaphragm and ports
PCM Diagnostics Trouble Code (DTC) Index
DTC Description Source Action P0442 Small leak detected in EVAP system (As small as 1.02 mm [0.040 inch]) PCM
Go To Pinpoint Test A . P0455 Major leak or no flow detected PCM
Go To Pinpoint Test B . P0457 Check for missing or leaking fuel filter cap PCM
Go To Pinpoint Test A . P1443 Very small or no purge flow detected PCM
Go To Pinpoint Test B . P1450 Excessive vacuum detected in the fuel tank PCM
Go To Pinpoint Test C . — Any other PCM DTC PCM REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.
Test Step Result / Action to Take
NOTE: Condition DTC P0455 set: –1.74 kPa (-7.0 inches H 2 O) over 30 seconds.
NOTE: Condition DTC P1443 set: –1.74 kPa (-7.0 inches H 2 O) over 30 seconds with more than 0.02 lb/min vapor flow.
B1 CHECK FOR DIAGNOSTIC TROUBLE CODE P0455 OR P1443 - Use the recorded results from the PCM DTCs.
- Is DTC P0455 present?
Yes
GO to
B2 .
No
GO to
B3 .
B2 VISUALLY CHECK FOR GROSS EVAP SYSTEM LEAKS - Check for the presence of a fuel filler cap. Do not tighten or check for correct installation at this time.
- Check the input port vacuum and EVAP return tube are connected to the EVAP canister purge valve.
- Check that the canister vent solenoid is correctly attached to the EVAP canister.
- Check for disconnected or cracked fuel vapor hoses or tubes between the intake manifold and following components:
- EVAP canister purge valve
- fuel vapor vent valve assembly
- fuel vapor control valve tube assembly
- Check for damaged fuel tank or fuel filler pipe.
- Is a concern with a hose, tube, connection or valve visually evident?
Yes
REPAIR or INSTALL new EVAP components as necessary. GO to
B3 .
No
GO to
B3 .
B3 CHECK FOR EVAP SYSTEM LEAKS - Disconnect the EVAP return tube from the intake manifold and plug the EVAP return tube.
- Connect the Evaporative Emissions System Leak Tester to the EVAP test port.
- Carry out the evaporative emissions system leak test. Refer to Evaporative Emission System Leak Test in this section.
- Does the system pressure stay above 1.99 kPa (8 inches H 2 O)?
Yes
GO to
B4 .
No
VERIFY that the fuel filler cap is installed correctly. REPAIR or INSTALL new components as necessary. CARRY OUT the evaporative emission system leak test. REFER to
Evaporative Emission System Leak Test in this section. If the system passes the leak test, CARRY OUT the evaporative emission repair verification drive cycle. REFER to
Evaporative Emission Repair Verification Drive Cycle in this section.
B4 CHECK FOR BLOCKAGE BETWEEN THE EVAP CANISTER PURGE VALVE AND FUEL VAPOR TEE Yes
GO to
B5 .
No
INSTALL a new vapor line between the EVAP canister purge valve and the fuel vapor tee. CARRY OUT the evaporative emission system leak test. REFER to
Evaporative Emission System Leak Test in this section. If the system passes the leak test, CARRY OUT the evaporative emission repair verification drive cycle. REFER to
Evaporative Emission Repair Verification Drive Cycle in this section.
B5 CHECK FOR BLOCKAGE BETWEEN FUEL FILLER PIPE AND THE FUEL VAPOR TEE - Connect the Evaporative Emissions System Leak Tester to the fuel filler pipe.
- Pressurize the EVAP system to 6.47 to 6.97 kPa (26 to 28 inches H 2 O).
- Does the pressure drop immediately?
Yes
GO to
B6 .
No
INSTALL new fuel tank vapor line(s). REPEAT pinpoint test Step B5 to verify the repair. CARRY OUT the evaporative emission system leak test. REFER to
Evaporative Emission System Leak Test in this section. If the system passes the leak test, CARRY OUT the evaporative emission repair verification drive cycle. REFER to
Evaporative Emission Repair Verification Drive Cycle in this section.
B6 CHECK FOR FAILED EVAP CANISTER PURGE VALVE OR FUEL TANK PRESSURE SENSOR - Use the recorded results from the PCM DTCs.
- Are DTC codes P0455 and P1443 present?
Yes
INSTALL a new EVAP canister purge valve. REFER to
Evaporative Emission Canister Purge Valve in this section. CARRY OUT the evaporative emission system leak test. REFER to
Evaporative Emission System Leak Test in this section. If no leak is detected, CARRY OUT the evaporative emissions repair verification drive cycle. REFER to
Evaporative Emission Repair Verification Drive Cycle in this section.
No
INSTALL a new fuel tank pressure sensor. REFER to
Fuel Tank Pressure Sensor in this section. CARRY OUT the evaporative emission system leak test. REFER to
Evaporative Emission System Leak Test in this section. If the system passes the leak test, CARRY out the evaporative emission repair verification drive cycle. REFER to
Evaporative Emission Repair Verification Drive Cycle in this section.
97 cobra, code 1443, please help 
