TECHNICAL SERVICE BULLETIN
SB-18-001 LOW POWER UNCOMMANDED STOP
LAMP ILLUMINATION
GROUP: 0-GENERAL
BULLETIN NO: SB-18-001
DATE: 1-3-2018
REFERENCE: HMM-170912-B1

SUBJECT VEHICLES: 05MY-18MY Conventional Trucks equipped

with air brakes.
Note: This service bulletin is provided as technical information
and is not authorization for a warrantable repair.
OVERVIEW:

The subject vehicle may experience low power and/or an
uncommanded stop lamp illumination. An enhanced brake pedal
return spring is available to maintain the brake pedal static
position. This procedure provides direction for installation of the
brake pedal return spring and brake lamp switch adjustment.

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.

PARTS:
PART NUMBER

PART DESCRIPTION

QUANTITY

SZ50840002

Spring, Torsion

1

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. To prevent damage during brake pedal removal, rotate the stop lamp
switch 1/8 turn counterclockwise and remove from the brake pedal bracket.
Disconnect the switch electrical connector and set the switch aside.

2. There is a retaining clip on each end of the brake pedal pivot shaft.
Remove both of these clips and retain for reassembly. The right side
retaining clip is circled in the photograph below right.

3. To allow the brake pedal pivot shaft to be moved far enough left (driver’s
side) to remove the brake pedal, a pair of wire harness connectors must be
disconnected from the kick panel. Insert a pocket screwdriver as shown
below and pry gently. Pull downwards on the connectors to remove.

4. Slide the brake pedal pivot shaft all the way to the left side of the vehicle
(driver’s side) and remove the brake pedal from the vehicle.

5. Remove the old brake pedal return spring from the brake pedal and
discard the return spring.

6. Remove the two bushings from the brake pedal and wipe clean. Apply a
light coating of lithium based grease to the inside and outside of the
bushings, and reinstall these into the brake pedal.

7. Install the new brake pedal return spring as shown in the photograph
below.

8. Begin brake pedal reinstallation by inserting the brake pedal pushrod
into the boot on the brake valve. The new brake pedal return spring will
anchor in the vehicle in a different location than the old spring. See
photographs below. Depress the end of the brake pedal return spring to
allow the spring fit under the flange of the brake plate during pedal
reinstallation. Slide the brake pedal pivot shaft back into position.

9. Reinstall the two brake pedal pivot shaft retaining clips.
NOTICE: Ensure both retaining clips are properly seated.

10. Reattach the two electrical connectors to the mounting clip on the kick
panel.

11. Measure the brake pedal push rod to brake valve free play using a
metric ruler at the center of the brake pedal. Free play should be 1 – 4mm.
If the free play is correct, proceed to step 13. If the free play is incorrect,
continue to step 12.

12. Loosen the jam nut on the brake pedal pushrod. Adjust the brake pedal
pushrod to achieve 1 – 4mm of brake pedal free play. Tighten the jam nut
to the specified torque.
Specified Torque: 18 lb-ft (25Nm)

13. Reconnect the stop lamp switch electrical connector. While holding up
on the brake pedal, insert the stop lamp switch until the switch body
contacts the pedal. Rotate the stop lamp switch 1/8 turn to the right to lock
in place.

14. With the brake pedal released, measure the gap between the pedal
and the stop lamp switch housing using a feeler gauge. The clearance
should be 0.5 – 1.5mm (0.020 – 0.060in.). If the clearance is incorrect,
remove and reinstall the stop lamp switch as outlined in step 13.

FINAL INSPECTION:
1.
•
•
•
•

To complete this TSB review and confirm the following:
Brake pedal free play measures 1 – 4mm
The stop lamp operates properly when applying and releasing the
brake pedal
The brake pedal pivot shaft retaining clips are properly installed
The stop lamp switch is securely locked in place.

NOTE: This procedure is provided as technical information and is not an
authorization for a warranty repair.
CLAIM APPLICATION:
* Reimbursable in accordance within the terms and policies of the Hino
Truck limited warranties.
Brake Pedal Return Spring Replacement:
a) Labor charge: 2.1 Hr.
b) Warranty code: 31511
c) Trouble code: 72
d) Operation code: 31507BRE
e) Original failed part: 9999999999