Hino P2201 Fault Code: Nox Sensor (SCR Upstream) – Performance

Technical Description

• NOx sensor 1 (SCR upstream) confirms correct value by comparing with the actual NOx sensor 1 (SCR upstream) value, the NOx sensor 2 (SCR downstream) value and the NOx model value calculated by the ECU.
• NOx model value is calculated according to the engine’s state and properties.
• At low NOx concentration, NOx sensor 1 (SCR upstream) confirms correct value by comparing with the Judgement criteria.

Description Of Malfunction

Characteristics failure of NOx sensor 1 (SCR upstream) is detected.

DTC Set Condition

DTC Detection Condition:

• DPF active regeneration in process.
• DPF upstream temperature ≥ 400°C {752°F}.
• 75 kPa ≤ Barometric pressure ≤ 112 kPa.
• -7°C {19.4°F} ≤ Intake air temperature (build-in air flow sensor) ≤ 49°C {120°F}.
• 55°C {131°F} ≤ Engine coolant temperature ≤ 100°C {212°F}.
• NOx sensor (SCR upstream) is valid.
• NOx sensor (SCR downstream) is valid. 

Conditions below continue for 5 seconds:

• 100 ppm ≤ Calculated NOx (SCR upstream) ≤ 1,500 ppm.
• |ΔCalculated NOx (SCR upstream) | ≤ 1,172 ppm/sec.
• 300 kg/h ≤ Exhaust gas mass flow < 1,000 kg/h.
• Fuel injection quantity ≥ 5 mm3/st.

At low NOx concentration

Conditions below continue for 10 seconds:

• NOx sensor (SCR upstream) is valid.
• 120°C {248°F} < SCR catalyst temperature < 170°C {338°F}.
• DPF active regeneration in not process.
• Estimated current NH3 load in SCR – Normal value of NH3 load in SCR ≤ 0 g.
• -0.5°C {31°F}/sec ≤ SCR catalyst temperature gradient ≤ 0.25°C {32°F}/sec.
• 1,000 r/min ≤ Engine speed ≤ 3,000 r/min.
• Cumulative Exhaust gas mass flow > 1,000 g from Fuel injection quantity ≤ 0 mm3/st.

Judgment Criteria:

All of the three conditions described below are formed. (judgment time: 10 sec):

Average actual NOx (from NOx sensor 1 (SCR upstream)) / Average calculated NOx (SCR upstream): Out of range (< 0.4 or > 4).

At low NOx concentration

When any of the following conditions is satisfied and has continued for 5 seconds.

• Average actual NOx (from NOx sensor 1 (SCR upstream)) is above 40 ppm.
• Average actual NOx (from NOx sensor 1 (SCR upstream)) is below -40 ppm.

Reset Condition

After having restored to the normal conditions.

Indication, Warning Or System Control Regulation When The DTC Is Set

• MIL: ON
• SVS Light: OFF
• DEF injection is stopped.
• NOx reduction quantity monitoring is aborted.

Symptoms On The Vehicle When The DTC Is Set

Symptoms on the vehicle due to backup control (fail safe function)

Exhaust gas purification function is declined.

Pre – Inspection Work

Check if the battery voltage is in the normal range.

After – Inspection Work

• Clear all past DTCs.
• After starting the DPR automatic regeneration, form the DTC detection condition.
• Check if no DTC is stored after test drive.

Possible Causes

• Harness disconnection or short-circuit
• Failure of NOx sensor 1 (SCR upstream)
• NOx sensor 2 (SCR downstream) failure
  • Sensor internal circuit failure
  • NOx sensor controller failure
• Failure of sensor used in calculating model value:
  • Boost pressure sensor
  • Intake manifold temperature sensor
  • Engine coolant temperature sensor
  • EGR failure

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 system 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 P2201 has been detected.

Has any DTC related to P2201 been detected?

Step 2) Inspect the DEF.

Check the DEF concentration.

Are the measurements excessively different?

Step 3) Inspect the exhaust gas leakage.

Check the exhaust gas flow downstream of the turbocharger and confirm that there is no leakage of exhaust gas.

Step 4) 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 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 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]. Were any failures found?

Step 5) 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 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].

Were any failures found?

Step 6) Inspect the exhaust gas temperature sensor 4 (DPR inlet) connector.

Check the connection of the exhaust gas temperature sensor 4 (DPR inlet) connector (Looseness and poor contact).

Were any failures found?

Step 7) Inspect the exhaust gas temperature sensor 4 (DPR inlet).

1. Check the installation of the exhaust gas temperature sensor 4 (DPR inlet).
2. Make sure there is no dirt or damage to the exhaust gas temperature sensor 4 (DPR inlet).

Were any failures found?

Step 8) Inspect the exhaust gas temperature sensor 4 (DPR inlet) unit.

1. Set the starter switch to the “LOCK” position.
2. Disconnect the exhaust gas temperature sensor 4 (DPR inlet) connector.
3. Use the electrical tester to measure the resistance between the terminals of the exhaust gas temperature sensor 4 (DPR inlet).

Do the measurements meet the standard value?

Step 9) Inspect the sensor power supply.

1. Set the starter switch to the “ON” position.
2. Use the electrical tester to measure the voltage between the terminals of the exhaust gas

temperature sensor 4 (DPR inlet) vehicle-side connector.

Do the measurements meet the standard value?

Step 10) Inspect for short-circuit of the exhaust gas temperature sensor 4 (DPR inlet) harness.

1. Set the starter switch to the “LOCK” position.
2. Connect the signal check harness to the engine ECU. (Do not connect harness to the ECU).
3. 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 11) Inspect disconnection of the exhaust gas temperature sensor 4 (DPR inlet) harness.

1. Connect the exhaust gas temperature sensor 4 (DPR inlet) connector.
2. Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness).

Do the measurements meet the standard value?

Step 12) 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 13) 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 14) 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 15) 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 16) 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 17) Inspect the DEF injector [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 muffler.
3. Connect the vehicle to the diagnostic tool.
4. Set the starter switch to the “ON” position.
5. Select [DCU].
6. Select [Inspection Menu] and check the DEF injector actuation.

• Select [Inspection Menu].
• Select [DEF solution addition test].
• Perform additional tests as instructed on the diagnostic tool screen. (Perform test patterns 1 – 3 and check the injection amount and spray condition).

Step 18) Check the response delay of the EGR valve [Diagnostic Tool].

1. Select [Engine] on the screen of the diagnostic tool.
2. Check the time lag (following characteristics) of the target EGR valve opening and actual EGR valve opening by following procedure.

CAUTION: Perform the inspection while the engine is stopped to avoid engine damages.

Inspection Procedure:

1. Select [Inspection Menu].
2. Select [EGR inspection].
3. Click [Start inspection].
4. Click [EGR opening UP]:

− Check each step from 0% – 90% of the time lag (following characteristics) of the target EGR valve opening and actual EGR valve opening.

5. Click [EGR opening DOWN]:

− Check each step from 90% – 0% of the time lag (following characteristics) of the target EGR valve opening and actual EGR valve opening.

NOTE: In EGR openings from 0% – 90%, 1 step corresponds to a 10 % change.

Do the measurements meet the standard value?

Step 19) Inspect the EGR valve [Diagnostic Tool].

1. Set the starter switch to the “LOCK” position.
2. Remove the EGR valve.
3. Set the starter switch to ON position and select [Engine] on the screen of the diagnostic tool.
4. Perform [EGR inspection] in the same way as Step 18. Confirm the tracking properties of the EGR valve and make sure it closes tightly.

Are tracking and tightness normal?

Step 20) Inspect the EGR cooler.

1. Check the condition of the tube coming out of the outlet side of the EGR cooler.
2. Check if the EGR cooler tube is clogged. Is the tube clogged?

Step 21) Inspect the air flow sensor connector.

Check the connection of the air flow sensor (Looseness and poor contact).

Were any failures found?

Step 22) 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 23) Inspect air flow sensor [Diagnostic Tool].

Prepare the new air flow sensor and compare the air flow sensor characteristics between the sensor on the vehicle and new sensor by using the diagnostic tool.

1. Set the starter switch to the lock position and connect the diagnostic tool to the vehicle.
2. Reconnect the sensor to the vehicle.
3. Set the starter switch to ON position and select [Engine] on the diagnostic tool menu.
4. Select [Amount of intake air flow inspection] from [Inspection Menu] on the diagnostic tool.
5. Perform [Amount of intake air flow inspection] as instructed on the diagnostic tool screen.
6. Perform the same inspection with the new sensor and compare the characteristics between old and new.

Do the measurements meet the standard value?

Step 24) Inspect for short-circuits in wire harness of air flow sensor.

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

NOTE: Measure while shaking the harness.

Do the measurements meet the standard value?

Step 25) Inspect for disconnection in wire harness of air flow sensor.

Use the electrical tester to measure the resistance between the engine ECU (signal check harness) terminal and the air flow sensor vehicle-side connector terminal.

NOTE: Measure while shaking the harness.

Do the measurements meet the standard value?

Step 26) Inspect the air flow sensor [Diagnostic Tool].

Prepare the new air flow sensor and compare the air flow sensor characteristics between the sensor on the vehicle and new sensor by using the diagnostic tool.

1. Set the starter switch to the “LOCK” position and connect the diagnostic tool to the vehicle.
2. Set the starter switch to “ON” position and select [Engine] on the diagnostic tool menu.
3. Select [Amount of intake air flow inspection] from [Inspection Menu] on the diagnostic tool menu.
4. Select [Amount of intake air flow inspection] from [Inspection Menu] on the diagnostic tool menu.
5. Perform the same inspection with the new sensor and compare the characteristics between old and new.

Do the measurements meet the standard value?

Step 27) Inspect the boost pressure sensor connector.

Check the connection of the boost pressure sensor connector (Looseness and poor contact).

Were any failures found?

Step 28) Inspect the boost pressure sensor.

1. Check the installation of the boost pressure sensor.
2. Make sure there is no dirt or damage to the boost pressure sensor.
3. Make sure there is no dirt, damage or clogging in the pipes or hoses unit of the boost pressure sensor.

Were any failures found?

Step 29) Check the boost pressure sensor output signal [Diagnostic Tool].

1. Set the starter switch to the “LOCK” position.
2. Connect the vehicle to the diagnostic tool.
3. Start the engine.
4. Select [Engine] from the menu.
5. Select [Actual boost pressure] from the [Data monitor setting] menu.
6. Race the engine from idle to NMR and verify that the boost pressure output signal varies.

Were there any abnormal changes in the sensor output signal?

Step 30) Inspect for short-circuits in wire harness of boost pressure sensor.

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

Do the measurements meet the standard value?

Step 31) Inspect for disconnection in wire harness of boost pressure sensor.

Use the electrical tester to measure the resistance between the engine ECU (signal check harness) and boost pressure sensor vehicle-side connector terminals.

Do the measurements meet the standard value?

Step 32) Inspect the boost pressure sensor power supply.

1. Connect the engine ECU vehicle-side 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 boost pressure sensor vehicle-side connector.

Do the measurements meet the standard value?

Step 33) Inspect the intake air temperature sensor (intake manifold) connector.

Check the connection of the intake air temperature sensor (intake manifold) connector (Looseness and poor contact).

Were any failures found?

Step 34) Inspect the intake air temperature sensor (intake manifold).

1. Check the installation of the intake air temperature sensor (intake manifold).
2. Make sure there is no dirt or damage to the intake air temperature sensor (intake manifold).

Were any failures found?

Step 35) Inspect the intake air temperature sensor (intake manifold) unit.

1. Set the starter switch to the “LOCK” position.
2. Disconnect the intake air temperature sensor (intake manifold) connector.
3. Use the electrical tester to measure the resistance between the terminals of the intake air

temperature sensor (intake manifold).

Do the measurements meet the standard value?

Step 36) Inspect the sensor power supply.

1. Set the starter switch to the “ON” position.
2. Use the electrical tester to measure the voltage between the terminals of the intake air temperature sensor (intake manifold) vehicle-side connector.

Do the measurements meet the standard value?

Step 37) Inspect for short-circuit of the intake air temperature sensor (intake manifold) harness.

1. Set the starter switch to the “LOCK” position.
2. Connect the signal check harness to the engine ECU. (Do not connect the harness to the ECU).
3. 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 38) Inspect disconnection of the intake air temperature sensor (intake manifold) harness.

1. Connect the intake air temperature sensor (intake manifold) connector.
2. Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness).

Do the measurements meet the standard value?

Step 39) Inspect the engine coolant temperature sensor 1 connector.

Check the connection of the engine coolant temperature sensor 1 connector (Looseness and poor contact).

Were any failures found?

Step 40) Inspect the engine coolant temperature sensor 1.

1. Check the installation of the engine coolant temperature sensor 1.
2. Make sure there is no dirt or damage to the engine coolant temperature sensor 1.

Step 41) Inspect the engine coolant temperature sensor 1 unit.

1. Set the starter switch to the “LOCK” position.
2. Disconnect the engine coolant temperature sensor 1 connector.
3. Use the electrical tester to measure the resistance between the terminals of the engine coolant temperature sensor 1.

Do the measurements meet the standard value?

Step 42) Inspect the engine coolant temperature sensor 1 power supply.

1. Set the starter switch to the “ON” position.
2. Use the electrical tester to measure the voltage between the terminals of the engine coolant temperature sensor 1 vehicle-side connector.

Do the measurements meet the standard value?

Step 43) Inspect for short-circuit of the engine coolant temperature sensor 1 harness.

1. Set the starter switch to the “LOCK” position.
2. Connect the signal check harness to the engine ECU. (Do not connect harness to the engine ECU).
3. 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 44) Inspect disconnection of the engine coolant temperature sensor 1 harness.

1. Connect the engine coolant temperature sensor 1 connector.
2. Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness).

Do the measurements meet the standard value?

Step 45) Inspect the engine coolant temperature sensor 2 connector.

Check the connection of the engine coolant temperature sensor 2 connector (Looseness and poor contact).

Were any failures found?

Step 46) Inspect the engine coolant temperature sensor 2.

1. Check the installation of the engine coolant temperature sensor 2.
2. Make sure there is no dirt or damage to the engine coolant temperature sensor 2.

Were any failures found?

Step 47) Inspect the engine coolant temperature sensor 2 unit.

1. Set the starter switch to the “LOCK” position.
2. Disconnect the engine coolant temperature sensor 2 connector.
3. Use the electrical tester to measure the resistance between the terminals of the engine coolant temperature sensor 2.

Do the measurements meet the standard value?

Step 48) Inspect the engine coolant temperature sensor 2 power supply.

1. Set the starter switch to the “ON” position.
2. Use the electrical tester to measure the voltage between the terminals of the engine coolant temperature sensor 2 vehicle-side connector.

Do the measurements meet the standard value?

Step 49) Inspect for short-circuit of the engine coolant temperature sensor 2 harness.

1. Set the starter switch to the “LOCK” position.
2. Connect the signal check harness to the engine ECU. (Do not connect harness to the engine ECU).
3. 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 50) Inspect disconnection of the engine coolant temperature sensor 2 harness.

1. Connect the engine coolant temperature sensor 2 harness.
2. Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness).

Do the measurements meet the standard value?

Step 51) Check the DTC detected (Engine ECU) [Diagnostic Tool].

1. Replace the NOx sensor 1 (SCR upstream) and NOx sensor 2 (SCR downstream).
2. Clear all past DTCs.
3. Check that no DTC is detected after test drive.
4. Stop the engine and set the starter switch to the “LOCK” position.
5. Connect the vehicle to the diagnostic tool.
6. Set the starter switch to the “ON” position.
7. Select [Engine] and check if P2201 has been detected.

Has DTC P2201 been detected?

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