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DTC P1438-92: Fuel Tank Pressure Too High
 
 
 
 
TECHNICAL DESCRIPTION
  • The ECM monitors the signals input from the fuel tank pressure sensor.
  • Based on the input signals, the ECM checks whether the pressure in the fuel tank exceeds the maximum withstand pressure of the system.
 
 
DTC SET CONDITIONS
Check Condition
  • Power supply mode of electric motor switch: ON.
Judgment Criterion
  • Fuel tank pressure is more than 48 kPa (14.2 in.Hg) for 4 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
None.
 
 
OBD-II DRIVE CYCLE PATTERN
None.
 
 
TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CODE TO BE SET ARE:)
  • Vapor line or purge line is clogged.
  • Fuel tank solenoid valve failed.
  • Bypass valve [built into the evaporative emission canister (main)] failed.
  • Fuel tank pressure sensor failed.
  • Fuel tank pressure sensor circuit harness damage, or connector damage.
  • Evaporative emission purge solenoid failed.
  • Barometric pressure sensor failed.
  • ECM failed.
 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
1.STEP 1. Using scan tool (M.U.T.-III SE), read the DTC.
Use scan tool (M.U.T.-III SE) to check and see if a DTC other than P1438-92 is set.
Q: Is DTC other than P1438-92 set?
Perform troubleshooting for the set DTC (Refer to DIAGNOSTIC TROUBLE CODE CHART).
 
2.STEP 2. Using scan tool (M.U.T.-III SE), check the data list.
Use scan tool (M.U.T.-III SE) to check the data list (Refer to DATA LIST REFERENCE TABLE).
  • Item number 850: EVAP System Absolute Pressure Sensor
Q: Is the check result normal?
 
3.STEP 3. Check harness between fuel tank pressure sensor connector terminal number 1 and ECM connector terminal number 78, check harness between fuel tank pressure sensor connector terminal number 2 and ECM connector terminal number 88, and check harness between fuel tank pressure sensor connector terminal number 3 and ECM connector terminal number 77.
Check signal line for open/short circuit and damage.
Q: Are the check result normal?
Replace the fuel tank pressure sensor (Refer to ENGINE, Fuel Supply – Fuel Tank FUEL TANK DISASSEMBLY AND ASSEMBLY). Then
Repair or replace the connector, or repair the damaged harness wire.
 
4.STEP 4. Check the bypass valve for clogs.
Check the bypass valve for stuck closed (Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Evaporative Emission System CANISTER PLUGGED OR DAMAGE INSPECTION).
Q: Is the check result normal?
 
5.STEP 5. Check harness between ECM connector terminal number 66 and bypass valve connector terminal number 1.
Check ground line for short to power supply.
Q: Is the check result normal?
Replace the evaporative emission canister (main) (integrated with bypass valve) (Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Evaporative Emission System EVAPORATIVE EMISSION CANISTER REMOVAL AND INSTALLATION). Then
Repair or replace the connector, or repair the damaged harness wire.
 
6.STEP 6. Check the relief valve for clogs.
Check the relief valve of the fuel tank solenoid valve for stuck closed (Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Evaporative Emission System FUEL TANK SOLENOID VALVE CHECK).
Q: Is the check result normal?
Replace the evaporative emission canister (main) (integrated with relief valve) (Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Evaporative Emission System FUEL TANK SOLENOID VALVE REPLACEMENT).
 
7.STEP 7. Check tube F clogging between the fuel tank solenoid valve and fuel tank.
(1) Drain the fuel from the fuel tank.
(2) Use a hand vacuum pump to check the tube F.
Q: Is the tube F ventilation?
Repair or replace the tube F.
 
8.STEP 8. Check piping clogging between the evaporative emission purge solenoid and fuel tank solenoid valve.
(1) Disconnect the tube E in the fuel tank solenoid valve.
(2) Disconnect the hose B from evaporative emission purge solenoid and mount the hand vacuum pump on the hose side.
(3) When negative pressure is applied with the hand vacuum pump, check that there is ventilation and no clogging.
Q: Are the hoses, tubes and pipes in good condition?
Repair or replace the hose, tube or pipe.
 
9.STEP 9. Check hose A clogging between the evaporative emission purge solenoid and intake manifold.
Remove the hose A, and use a hand vacuum pump to check hose A.
Q: Is the hose A in good condition?
Repair or replace the hose A.
 
10.STEP 10. Check the evaporative emission purge solenoid for clogs.
Check evaporative emission purge solenoid itself (Refer to ENGINE, Engine, Motor and Emission Control – Emission Control – Evaporative Emission System EVAPORATIVE EMISSION PURGE SOLENOID CHECK).
Q: Is there ventilation of the evaporative emission purge solenoid?
Replace the evaporative emission purge solenoid (Refer to ENGINE, Intake and Exhaust – Intake Manifold INTAKE MANIFOLD REMOVAL AND INSTALLATION).
 
11.STEP 11. Using scan tool (M.U.T.-III SE), DTC recheck after erasing DTC.
After erasing the DTC, check again to see if the DTC is set again.
(1) Use scan tool (M.U.T.-III SE) to erase the DTC.
(2) Turn OFF the power supply mode of the electric motor switch.
(3) Turn ON the power supply mode of the electric motor switch.
(4) Use scan tool (M.U.T.-III SE) to recheck the DTC.
Q: Is DTC P1438-92 set?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
Intermittent malfunction (Refer to GENERAL INFORMATION, General Information – How to Use Troubleshooting/Inspection Service Points – How to Cope with Intermittent Malfunctions HOW TO COPE WITH INTERMITTENT MALFUNCTIONS).
 
12.STEP 12. Using scan tool (M.U.T.-III SE), DTC recheck after erasing DTC.
After erasing the DTC, check again to see if the DTC is set again.
(1) Use scan tool (M.U.T.-III SE) to erase the DTC.
(2) Turn OFF the power supply mode of the electric motor switch.
(3) Turn ON the power supply mode of the electric motor switch.
(4) Use scan tool (M.U.T.-III SE) to recheck the DTC.
Q: Is DTC P1438-92 set?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
The inspection is complete.