SERVICE BULLETIN
SB-20-001 P0421 DIAGNOSTIC TROUBLE CODE
(DTC) SERVICE BULLETIN
GROUP: 0-GENERAL
BULLETIN NO: SB-20-001
DATE: 3-19-2020

SUBJECT VEHICLES: Certain 16MY-20MY Cab-Over Engine

(COE) Trucks equipped with a J05 engine or Conventional Trucks
equipped with a J08 engine.

OVERVIEW:
If a truck comes to the dealer with a MIL lamp illuminated with the
Diagnostic Trouble Code (DTC): P0421 – Determination of ATC
Deterioration.
Replace the ATC as required following the repair procedure
below.
CONVENTIONAL PARTS:
Part Number
17401E0P30
17401E1550

Part Description
ATC Pipe (16MY17MY)
ATC Pipe (18MY20MY)

Quantity
1
1

S241091830

Gasket

1

21814E0140

Stud

4

21814E0290

Bolt

2

SZ17810012

Nut

2

S171041580

Gasket

1

SZ12608006

Stud

4

SZ17810007

Nut

4

17451E0100

Gasket

1

S171041580

Gasket

2

COE PARTS:
Part Number

Part Description

Quantity

17401E1230

ATC Pipe (16MY-17MY)

1

1740E1450

ATC Pipe (18MY-20MY)

1

1745178061

Gasket

1

17451E0110

Gasket

1

SZ11610171

Stud

3

SZ91016223

Washer

3

SZ17810007

Nut

3

9011910817

Bolt

3

BEFORE YOU BEGIN:
- Read and understand all instructions and procedures before you
begin the work.
- Read and follow all WARNINGS and NOTICES set forth in this
publication. These alerts help to avoid damage to components,
serious personal injury, or both.
- Park the vehicle on a flat, level and solid surface.
- Place the gear shift lever in "Neutral" or "Park".
- Apply the parking brake firmly and confirm parking brake
activation.
- Turn off the engine and remove the key from the ignition switch.
- Always wear safety glasses or goggles to protect your eyes.
- Place wheel chocks in front of and behind all the wheels to
prevent the vehicle from moving.
VEHICLE PREPARATION:
1. Park the vehicle on a flat, level and solid surface.

2. Confirm the engine is stopped, the ignition switch is in the off (LOCK)
position, and the key is removed.

3. Apply the parking brake.

4. Chock all of the wheels.

REPAIR PROCEDURE:
1. Prepare a DXII compatible interface, such as the Denso DST-i
or the Nexiq USB Link 2 to perform this procedure.
To assemble the interface cable, perform the following steps.
(1) Connect the DLC (Diagnostic Link Connector) cable to the
interface.
(2) Connect the USB Cable to the interface.
(3) Connect the USB connector to the USB port on your
computer.

2. Connect the DLC cable to the vehicle’s DLC connector. The
DLC connector is found under the dash on the left side of the
steering column. Check for the P0421 code.

3. Check the exhaust brake adjustment. For additional
information, refer to TT-19-005.

4. Remove the right hand side inner fender.
5. Replace the ATC catalyst pipe.
REMOVAL
Remove the exhaust pipe No.1 (ATC)
NOTICE: The ATC will have to be replaced together with the
exhaust pipe No.1 (ATC).
Remove the exhaust pipe No.2
Remove the bolts and nuts on the flange on the muffler unit side.
Remove the after treatment system.

Disconnect the exhaust gas temperature sensor 1 (ATC
Upstream) of the connector and the exhaust gas temperature
sensor 2 (ATC Downstream) of the connector.

Remove the exhaust pipe No.1 (ATC)
(1) Unfasten the bolts (4 pcs.) to remove the bracket from the
exhaust
pipe No.1 (ATC).
(2) Unfasten the nuts (3 pcs.) to remove the exhaust pipe No.1
(ATC) and
gasket from the exhaust brake.

INSTALLATION
NOTICE: The ATC will have to be replaced together with the
exhaust pipe No.1 (ATC).
Mounting the exhaust pipe No.1 (ATC)
(1) Replace with a new gasket and temporarily tighten the
exhaust pipe No.1 (ATC) to the exhaust brake with nuts (4 pcs.).
(2) Temporarily tighten the bracket with the bolts.
(3) Tighten the bracket fully.
Tightening Torque: 55 Nm {40.6 lb-ft}
(4) Tighten the exhaust pipe No.1 (ATC) fully.
Tightening Torque: 70 Nm {52 lb-ft}

Connect the exhaust gas temperature sensor 1 (ATC
UPSTREAM) of connector and exhaust gas temperature sensor 2
(ATC DOWNSTREAM) of connector.

MOUNTING THE AFTERTREATMENT FUEL INJECTOR
Reference: EXHAUST SYSTEM (J08E)/(J05E),
AFTERTREATMENT FUEL INJECTOR, OVERHAUL,
MOUNTING AFTERTREATMENT FUEL INJECTOR
CONNECTING THE EXHAUST PIPE No.2
(1) Tighten the exhaust pipe No.2 fully.
Tightening Torque: 56-84 Nm {41.3-61.9 lb-ft}

FINAL INSPECTION:
1. To complete this procedure review the steps of the repair
procedure and confirm the following:
• All nuts and bolts have been tightened to their specified torque
• There are no exhaust leaks present
• Using Hino DX2, ensure all codes have been cleared prior to
releasing the truck back to the customer.
Note: This technical service bulletin is provided as technical
information and is not authorization for a warrantable repair.
CLAIM APPLICATION
Reimbursable in accordance within the terms and policies of the
Hino limited warranties.
ATC Diagnosis and Replacement:
a) Total Labor charge: Conventional 3.6 hrs. and COE 3.0 hrs.
b) Warranty code: 11316
c) Trouble code: 40
d) Operation codes: See Below
11350AOT DX Diagnosis/Codes
0.2
11250AOT Exhaust Brake Check/Adjustment 0.5
11301CRE ATC Replacement 2.9 (Conv.) / 2.3 (COE)