Hino P20EE fault code: Nox converting catalyst conversion efficiency

TECHNICAL DESCRIPTION

• Deterioration of SCR catalyst is determined by a decision of a drop in the NOx conversion efficiency and the DEF concentration.
• Conversion efficiency is calculated by upstream and downstream NOx sensors.
• Besides other factors, conversion efficiency may drop due to the increase or decrease of DEF amount supplied to the sensing unit.
• DEF SCR catalyst concentration is measured by a DEF quality sensor.

DTC SET CONDITION

DTC Detection Condition:

Conditions below continue for 5 seconds:

• 1,000 r/min ≤ Engine speed ≤ 2,500 r/min
• Engine speed ≥ 300 r/min for 3 seconds.
• 30 mm3/st. cyl. ≤ Fuel injection quantity < 150 mm3/st. cyl.
• 300 kg/h ≤ Exhaust gas mass flow 1000 kg/h.
• 210°C {410°F} ≤ SCR catalyst temperature < 260°C {500°F}.
• 50 ppm ≤ NOx (SCR upstream) < 1000 ppm.
• Intake air temperature > -20°C {-4°F}.
• 60 % ≤ Ratio of actual NH3 load < 120%.
• Calculated HC load < 0.1 g.
• NOx sensor 1 (SCR upstream) and NOx sensor 2 (SCR downstream) are valid for 121 seconds.
• DPF active regeneration not in process.

Conditions below continue for 10 seconds:

• DEF defrosting completed (DEF take temperature) ≥ -5°C {23°F}.
• Exhaust gas temperature (SCR inlet) > 150°C {302°F}.
• Engine speed ≥ 350 r/min.
• Vehicle speed > 6.2 mph.
• 11 V < Battery voltage < 32 V.
• DEF quality sensor is valid.

Judgment Criteria:

The conditions described below are formed:

• Calculate Average NOx conversion efficiency from NOx sensor 1 (upstream) and 2 (downstream). Target NOx conversion efficiency (from DCU)
• Average NOx conversion efficiency ≥ 0.99.
• Average DEF concentration > 16%.

RESET CONDITION

• Immediately after normal operation is restored and SCR-related memory is reset.

INDICATION, WARNING OR SYSTEM CONTROL REGULATION WHEN THE DTC IS SET

• MIL: ON
• SVS Light: OFF
• Engine output is restricted.
• Vehicle speed is restricted.

PRE-INSPECTION WORK

• Check that the battery voltage is in the normal range.

AFTER-INSPECTION WORK

• Clear all past DTCs.
• Form the DTC detection condition.
• Check that no DTC is detected after test drive.

POSSIBLE CAUSES

• Faulty DEF solution reduction.
• Harness disconnection or short-circuit.
• NOx sensor failure.
• Air flow sensor failure.
• Exhaust gas temperature sensor (SCR inlet) failure.
• DEF quality sensor failure.
• SCR catalyst: miscalculation of adsorption amount or HC poisoning.

NOTE: If no trouble causes are found, it can be suspected that the respective DTC was issued because of a temporary fault condition caused by the freezing of the DEF.

INSPECTION PROCEDURE

TROUBLESHOOTING STEPS

Step 1) Check the DTC detected [Diagnostic Tool].

1. Set the starter switch to the “LOCK” position.
2. Connect the diagnostic tool to the vehicle.
3. Set the starter switch to the “ON” position.
4. Select [Engine] on the screen of the diagnostic tool and check it the DTC P20EE has been detected.

Has any DTC related to P20EE been detected ?

Step 2) Check the DEF solution Check the DEF solution concentration.

Do the measurements meet the standard value?

Step 3) Inspect the NOx sensor No.1 (SCR upstream) [Diagnostic Tool].

1. Turn the starter key to the “ON” position.
2. Start the diagnostic tool.
3. On the diagnostic tool window, click [Diagnosis]. Select the vehicle model and region, and check [Engine]. Select either Upload INF file and then [Read out] to read out.
4. Select [Engine] and press the click button.
5. Writing soot volume.

NOTE: Write a soot volume [2.0] using the customization function. Record the original value not to forget.

6. Turn the starter key “OFF” and then “ON” according to the instruction. Then, click [OK].
7. Check that ECU writing has been completed. Click [OK].
8. Start monitoring using the data monitoring function of the diagnostic tool. Check the output waveform of the NOx sensor on the monitor.
9. Select [Data monitor and Active test].
10. Select [Data monitor setting].
11. Select the following 4 items. Click OK.

• NOx level (before catalyst)
• NOx level (after catalyst)
• SCR catalyst exhaust gas temperature (DCU reception)
• Water temperature sensor 2

12. Click [Start] to display the window to check the data storage destination. Click [OK] to start data monitoring.
13. Start the engine.
14. Press the DPR manual regeneration switch of the vehicle. Start regeneration.

NOTE: Since NOx sensor waveform is not detected until the exhaust gas temperature and coolant temperature reach the specified values or more, perform DPR regeneration to increase the exhaust gas temperature and coolant temperature.

15. On the diagnostic tool data monitor, monitor the SCR catalyst temperature, coolant temperature and NOx levels before and after.
16. When the SCR catalyst temperature reaches 250ºC {482ºF} and coolant temperature reaches 70ºC {158ºF}, press the DPR switch (button) to stop the regeneration.
17. Following the determination information, determine the quality of the sensor according to the NOx sensor waveform data on the monitor. This is the end of the troubleshooting.
18. Turn the starter key OFF once to stop the engine. Turn it ON again.
19. After completing the troubleshooting, rewrite the soot volume to the original value. Select [Engine].
20. Rewrite the soot volume to the recorded original value. The soot volume to write is [0.6].
21. Check that the original soot volume has been written and click [OK].
22. Select [System protection data] to check [Manual regeneration completion frequency]. Click [Reset].

NOTE: Unless this memory reset is performed, the DTC of abnormal regeneration frequency would turn on.

23. Check that the memory reset has been completed. Click [OK].

Does the NOx controller operate properly ?

Step 4) Inspect the NOx sensor No.2 (SCR downstream) [Diagnostic Tool].

1. Turn the starter key to the “ON” position.
2. Start the diagnostic tool.
3. On the diagnostic tool window, click [Diagnosis]. Select the vehicle model and region, and check [Engine]. Select either Upload INF file and then [Read out] to read out.
4. Select [Engine] and press the click button.
5. Writing soot volume.

NOTE: Write a soot volume [2.0] using the customization function. Record the original value not to forget.

6. Turn the starter key “OFF” and then “ON” according to the instruction. Then, click [OK].
7. Check that ECU writing has been completed. Click [OK].
8. Start monitoring using the data monitoring function of the diagnostic tool. Check the output waveform of the NOx sensor on the monitor.
9. Select [Data monitor and Active test].
10. Select [Data monitor setting].
11. Select the following 4 items. Click OK.

• NOx level (before catalyst)
• NOx level (after catalyst)
• SCR catalyst exhaust gas temperature (DCU reception)
• Water temperature sensor 2

12. Click [Start] to display the window to check the data storage destination. Click [OK] to start data monitoring.
13. Start the engine.
14. Press the DPR manual regeneration switch of the vehicle. Start regeneration.

NOTE: Since NOx sensor waveform is not detected until the exhaust gas temperature and coolant temperature reach the specified values or more, perform DPR regeneration to increase the exhaust gas temperature and coolant temperature.

15. On the diagnostic tool data monitor, monitor the SCR catalyst temperature, coolant temperature and NOx levels before and after.
16. When the SCR catalyst temperature reaches 250°C {482°F} and coolant temperature reaches 70°C {158°F}, press the DPR switch (button) to stop the regeneration.
17. Following the determination manual, determine the quality of the sensor according to the NOx sensor waveform data on the monitor. This is the end of the troubleshooting.
18. Turn the starter key OFF once to stop the engine. Turn it ON again.
19. After completing the troubleshooting, rewrite the soot volume to the original value. Select [Engine].
20. Rewrite the soot volume to the recorded original value. The soot volume to write is [0.6].
21. Check that the original soot volume has been written and click [OK].
22. Select [System protection data] to check [Manual regeneration completion frequency]. Click [Reset].

NOTE: Unless this memory reset is performed, the DTC of abnormal regeneration frequency would turn on.

23. Check that the memory reset has been completed. Click [OK].

Does the NOx controller operate properly ?

Step 5) Inspect the DEF tank.

1. Remove the DEF tank from the vehicle.
2. Remove the DEF quality sensor from the DEF tank.
3. Drain the DEF solution from the DEF tank and check the tank interior for the presence of foreign substances.

Were any failures found ?

Step 6) Check the DEF quality sensor. Make sure there is no dirt or damage to the DEF quality sensor. Were any failures found ?

Step 7) Check the DTC detected (Engine ECU) [Diagnostic Tool].

1. Temporarily install the DEF quality sensor in the DEF tank and mount the tank on the vehicle. (This makes it possible to connect the DEF quality sensor connector).
2. Fill the tank with the standard concentration of DEF solution.
3. Clear all past DTCs.
4. Check that no DTC is detected after test drive.
5. Connect the vehicle to the diagnostic tool.
6. Set the starter switch to the “ON” position.
7. Select [Engine] and check if DTC P20EE has been detected.

Has DTC P20EE been detected?

Step 8) Inspect the exhaust gas temperature sensor (SCR inlet) connector.

Check the connection of the exhaust gas temperature sensor (SCR inlet) connector (Looseness and poor contact). Were any failures found ?

Step 9) Inspect the exhaust gas temperature sensor (SCR inlet).

1. Check the installation of the exhaust gas temperature sensor (SCR inlet).
2. Make sure there is no dirt or damage to the exhaust gas temperature sensor (SCR inlet).

Were any failures found ?

Step 10) Inspect the exhaust gas temperature sensor (SCR inlet) unit.

1. Set the starter switch to the “LOCK” position.
2. Disconnect the exhaust gas temperature sensor (SCR inlet) connector.
3. Use the electrical tester to measure the resistance between the terminals of the exhaust gas temperature sensor (SCR inlet).

Do the measurements meet the standard value ?

Step 11) Inspect for short-circuit in the exhaust gas temperature sensor (SCR inlet) harness.

1. Disconnect the DCU 86P connector.
2. Connect the signal check harness and use the electrical tester to measure the resistance between the terminals of the DCU 86P vehicle-side connector and the ground.

Do the measurements meet the standard value ?

Step 12) Inspect disconnection of the exhaust gas temperature sensor (SCR inlet) harness.

1. Connect the exhaust gas temperature sensor (SCR inlet) connector.
2. Connect the signal check harness and use the electrical tester to measure the resistance between the terminals of the DCU 86P vehicle-side connector.

Do the measurements meet the standard value ?

Step 13) Check the DEF pipe (pump ↔ injector). Check the DEF pipe (pressure line) and verify that there are no disconnections, clogging, corrosion, or cracks. Were any failures found ?

Step 14) Inspect the DEF injector 1 [Diagnostic Tool]. NOTE: Prepare a beaker or similar, plus a larger measuring vessel for measuring the DEF to be injected, before performing this inspection. (If the vessel is small, there is dispersion at the time of injection from the injector, and the measuring quantity decreases).

1. Set the starter switch to the “LOCK” position.
2. Remove the DEF injector from the muffler.

NOTE: Refer to the section selective catalytic reduction (SCR) information for removal and installation of the DEF injector.

3. Connect the vehicle to the diagnostic tool.
4. Set the starter switch to the “ON” position.
5. Select [DCU].
6. Select [Inspection Menu] on the diagnostic tool menu and check the operation of the DEF injector.

NOTE: When the DEF tank temperature is -5°C (23°F) or lower, perform warm-up to raise it to 10°C (50°F) or higher.

Inspection Procedure:

• Select [Inspection Menu].
• Select [DEF solution addition test].
• Perform DEF solution addition test as instructed on the diagnostic tool screen. (Perform all three patterns).

Is operation normal ?

Step 15) Inspect the DEF injector 2 [Diagnostic Tool].

1. Set the starter switch to the “LOCK” position.
2. Replace the DEF injector with a new one. (Do not install it on the muffler).
3. Set the starter switch to the “ON” position.
4. Perform DEF addition test as same as Step 14.

Is operation normal?

Step 16) Inspect the air flow sensor connector. Check the connection of the air flow sensor connector (Looseness and poor contact). Were any failures found ?

Step 17) Inspect the air flow sensor.

1. Check the installation of the air flow sensor.
2. Make sure there is no dirt or damage to the air flow sensor.

Were any failures found ?

Step 18) Inspect for short-circuit of the air flow sensor harness.

1. Set the starter switch to the “LOCK” position.
2. Connect the signal check harness to the engine ECU vehicle-side harness. (Do not connect the harness to the ECU).
3. Disconnect the air flow sensor connector.
4. Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness) and ground.

Do the measurements meet the standard value ?

Step 19) Inspect disconnection of the air flow sensor harness. Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness) and air flow sensor vehicle-side connector.

Do the measurements meet the standard value ?

Step 20) Inspect the air flow sensor power supply.

1. Connect the signal check harness to the engine ECU.
2. Set the starter switch to the “ON” position.
3. Use the electrical tester to measure the voltage between the terminals of the air flow sensor vehicle-side connector.

Were any failures found ?

Step 21) Inspect the air flow sensor signal.

1. Set the starter switch to the “LOCK” position.
2. Connect the air flow sensor connector.
3. Start the engine.
4. Use the oscilloscope to measure the signal voltage between the terminals in the engine ECU (signal check harness).

Do the measurements meet the standard value ?

Step 22) Perform a basic engine check. Perform a basic engine check. Refer to engine basic inspection information. Were any failures found ?

Step 23) Inspect the exhaust pipe. Make sure there is no soot leakage from the exhaust pipe outlet. Were any failures found ?

Step 24) Inspect the SCR catalyst [Diagnostic Tool].

1. Set the starter switch to the “LOCK” position.
2. Replace the SCR catalyst.
3. Set the starter switch to the “ON” position.
4. Erase the trouble history.
5. Form the DTC detection condition.
6. Select [Engine] and check if P20EE has been detected.

Has DTC P20EE been detected ?

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