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Hino P0421 Fault Code: Determination Of ATC Deterioration

25/01/2025

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TECHNICAL DESCRIPTION

If post injection is performed normally but the ATC (oxidation catalyst) is not generating heat, the engine ECU detects abnormality as ATC functional deterioration.

DTC SET CONDITION

DTC Detection Condition:

During DPR active regeneration.

Conditions below continue for 35 seconds:

Engine speed: 700 r/min or higher, 1,000 r/min or lower.
Fuel injection quantity: 40 mm3/st. or lower.
Engine speed fluctuation: 156 r/min/sec or lower.
Fuel injection quantity fluctuation: 39 mm3/st./sec or less.
Post-injection quantity: 17.5 mm3/st. or more.
ATC inlet temperature: 300°C (572°F) or higher.
Post injection has no malfunction.
Exhaust gas mass flow ≤ 210kg/h.

Judgment Criteria:

Both of the following conditions must be met:

ATC outlet temperature – ATC inlet temperature is below the specified value

RESET CONDITION

Immediately after normal status is resumed

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

MIL: ON
SVS light: OFF

PRE-INSPECTION WORK

Check that the battery voltage is in the normal range.

AFTER-INSPECTION WORK

Clear all past DTC.
After starting the DPR automatic regeneration, form the DTC detection condition.
Check that no DTC is detected after test drive.

POSSIBLE CAUSES

ATC deterioration caused by use of low-grade fuel
Improper adjustment of exhaust brake valve
Leak of exhaust gas from the pipe
ATC inlet exhaust gas temperature sensor malfunction
ATC outlet exhaust gas temperature sensor malfunction

INSPECTION PROCEDURE

TROUBLESHOOTING STEPS

Step 1: Check the engine ECU

Set the starter switch to the “LOCK” position
Check the engine ECU software part number using the diagnostic tool. Confirm the latest part number with OEM

Does the engine ECU have the latest software number?

Yes	Go to Step 2
No	Reprogram the engine ECU by using the diagnostic tool and then go to Step 2

Step 2: Inspect the exhaust leaks from the exhaust pipe between exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 3 (DOC inlet)

Check that the exhaust pipe has no looseness of flange or pipe breakage.

Were any failures found?

Yes	Repair or replace the faulty part. Clear all past DTCs. Check that no DTC is detected after test drive.
No	Go to Step 3

Step 3: Inspect the exhaust brake valve [Diagnostic Tool]

Warm up the engine. (Coolant temperature: 80°C (176°F) or more)
Turn OFF the devices that place load on the engine, such as the air conditioner.

Inspection Procedure:

Select [Engine] on the screen of the diagnostic tool.
Select [Data monitor setting] and [Active test setting].
Select [Target rpm] from [Active test setting] and set the engine revolution to 980 r/min.
Select [Injection quantity] from [Data monitor setting].
Turn ON/OFF the exhaust brake switch and check the difference between the injection quantity of the injector while the exhaust brake is working and the injection quantity when the exhaust brake is not actuated.

MEASUREMENT CONDITIONS	STANDARD VALUES
Engine revolution: 980r/min Engine coolant temperature: 80°C (176°F) or more. Turn OFF the air conditioner, and other devices that place load on the engine.	10– 14 mm3/st

Do the measurements meet the standard value? (There shall be a change in the

injection quantity between while the exhaust brake is working and when it is

not actuated).

Yes	Go to Step 4
No	Adjust the butterfly opening of the exhaust brake. Clear all past DTCs. Check that no DTC is detected after test drive.

Step 4: Inspect fuel

Open the fuel cap and check fuel for abnormality (in color is yellow or green).

Were any failures found?

Yes	Replace the fuel with good quality fuel. Clear all past DTCs. Check that no DTC is detected after test drive.
No	Go to Step 5

Step 5: Inspect the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream) connector

Check the connection of the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream) connector (looseness and poor contact).

Were any failures found?

Yes	Connect securely, repair if needed. Go to Step 6
No	Go to Step 6

Step 6: Inspect the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream)

Check the installation of the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream)
Make sure there is no dirt, damage or clogging in the sensing unit of the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream).

Were any failures found?

Yes	Clean the sensing unit and install it properly. If damaged, replace the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream). Go to Step 7.
No	Go to Step 7

Step 7: Inspect the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream) unit.

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

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch: LOCK

Exhaust gas temperature sensor 1 (ATC upstream): TEX5 – GND5

Exhaust gas temperature sensor 2 (ATC downstream): TEX3 – GND3

20°C {68°F}: 13.7 – 29.8 kΩ
50°C {122°F}: 7.13 – 13.7 kΩ
80°C {176°F}: 4.1 – 7.13 kΩ

Do the measurements meet the standard value?

Yes	Go to Step 8
No	Replace the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream). Go to Step 8.

Step 8: Inspect the sensor power supply

Set the starter switch to the “ON” position
Use the electrical tester to measure the voltage between the terminals of the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream) vehicle-side connector.

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch: ON

Exhaust gas temperature sensor 1 (ATC upstream) vehicle-side connector:

TEX5 – GND5

Exhaust gas temperature sensor 2 (ATC downstream) vehicle-side connector:

TEX3 – GND3

4.5 – 5.5 V

Do the measurements meet the standard value?

Yes	Go to Step 11. If any failure was found at steps 5 – 7, clear all past DTCs. Check that no DTC is detected after test drive.
No	Go to step 9

Step 9: Inspect for short-circuit of the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream) harness.

Set the starter switch to the “LOCK” position
Connect the signal check harness to the engine ECU. (Do not connect harness to the ECU)
Use the electrical tester to measure the resistance between the terminals of the engine ECU and ground

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch: LOCK

Engine ECU (signal check harness):

EXT+ (E43) – Ground
AG5 (E58) – Ground
KR2 (M50) – Ground

∞ Ω

Do the measurements meet the standard value?

Yes	Go to Step 10
No	Repair or replace the harness. Go to Step 10

Step 10: Inspect disconnection of the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream) harness

Connect the exhaust gas temperature sensor 1 (ATC upstream) and the exhaust gas temperature sensor 2 (ATC downstream) connector.
Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness)

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch: LOCK

Engine ECU (signal checkharness):

EXT+ (E43) – AG5 (E58)
KR2 (M50) – AG5 (E58)

20°C {68°F}: 13.7 – 29.8 kΩ
50°C {122°F}: 7.13 – 13.7 kΩ
80°C {176°F}: 4.1 – 7.13 kΩ

Do the measurements meet the standard value?

Yes	Go to Step 11. If any failure was found at the Steps 5 – 9, clear all past DTCs. Check that no DTC is detected after test drive.
No	Repair or replace the harness. Clear all past DTCs. Check that no DTC is detected after test drive.

Step 11: Inspect the exhaust gas temperature sensor 3 (DOC inlet) connector.

Check the connection of the exhaust gas temperature sensor 3 (DOC inlet) connector (looseness and poor contact)

Were any failures found?

Yes	Connect securely, repair if needed. Go to Step 12.
No	Go to Step 12.

Step 12: Inspect the exhaust gas temperature sensor 3 (DOC inlet)

Check the installation of the exhaust gas temperature sensor 3 (DOC inlet)
Make sure there is no dirt, damage or clogging in the sensing unit of the exhaust gas temperature sensor 3 (DOC inlet)

Were any failures found?

Yes	Clean the sensing unit and install it properly. If damaged, replace the exhaust gas temperature sensor 3 (DOC inlet). Go to Step 13
No	Go to Step 13

Step 13: Inspect the exhaust gas temperature sensor 3 (DOC inlet) unit

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

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch: LOCK

Exhaust gas temperature sensor 3 (DOC inlet):

TEX4 – GND4

20°C {68°F}: 13.7 – 29.8 kΩ
50°C {122°F}: 7.13 – 13.7 kΩ
80°C {176°F}: 4.1 – 7.13 kΩ

Do the measurements meet the standard value?

Yes	Go to Step 14.
No	Replace the exhaust gas temperature sensor 3 (DOC inlet). Go to Step 14.

Step 14: Inspect the sensor power supply

Set the starter switch to the “ON” position
Use the electrical tester to measure the voltage between the terminals of the exhaust gas temperature sensor 3 (DOC inlet) vehicle-side connector.

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch: LOCK

Engine ECU (signal check harness):

ET2+ (V49) – Ground
AGD3 (V46) – Ground

∞ Ω

Yes	Go to Step 17. If any failure was found at the step 11 – 13, clear all past DTCs. Check that no DTC is detected after test drive.
No	Go to Step 15.

Step 15: Inspect for short-circuit of the exhaust gas temperature sensor 3 (DOC inlet) harness.

Set the starter switch to the “LOCK” position
Connect the signal check harness to the engine ECU. (Do not connect harness to the ECU)
Use the electrical tester to measure the resistance between the terminals of the engine ECU and ground.

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch: LOCK

Engine ECU (signal check harness):

ET2+ (V49) – Ground
AGD3 (V46) – Ground

∞ Ω

Do the measurements meet the standard value?

Yes	Go to Step 17. If any failure was found at the step 11 – 15, Clear all past DTCs. Check that no DTC is detected after test drive.
No	Repair or replace the harness. Clear all past DTCs. Check that no DTC is detected after test drive.

Step 16: Inspect disconnection of the exhaust gas temperature sensor 3 (DOC inlet) harness

Connect the exhaust gas temperature sensor 3 (DOC inlet) connector
Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness)

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch: LOCK

Engine ECU (signal check harness):

ET2+ (V49) – AGD3 (V46)

20°C {68°F}: 13.7 – 29.8 kΩ
50°C {122°F}: 7.13 – 13.7 kΩ
80°C {176°F}: 4.1 – 7.13 kΩ

Yes	Replace the ATC
No	Procedure completed. (Temporary loose connection)

Step 17: Test drive

Set the starter switch to the “ON” position
Change the [DPR soot amount] using the diagnostic tool
Set the starter switch to the “LOCK” position
Monitor the [DPR mode] set
Start the test drive
Once the [DPR mode] reads any of “6, 7, 15, 23, 24, 27 or 28”, bring vehicle speed to “0” and keep idling for 60 seconds