TECHNICAL SERVICE BULLETIN

WATER PUMP CIRCUIT DIODE INSTALLATION

Job Code:
Date:

Product:

M920031 – 26-004

Repair Time:

5/20/2026

Lineage Series VP
0.2 h

Purpose
This bulletin describes the procedure to install a Grand Design RV – supplied diode into the water pump
control circuit of the Firefly Emprise electrical system on affected ProMaster LVP units. The diode
prevents excessive current in the water pump control circuit that can damage the Firefly circuit board.
NOTE: Actual color and finish of components may differ from those depicted in this document.

Background
On affected units, the Firefly circuit that controls the water pump can experience high current to the point of
damaging the Firefly circuit board. Installation of the supplied diode prevents this damage. Current production
units are wired to address this condition; this bulletin provides the field correction for units already in service.

Safety
This document provides general instructions. Many variables can change the circumstances of any procedure,
including the degree of difficulty involved in the service operation and the ability level of the individual performing
the operation. In the event the skill level required is too advanced or the procedure too difficult, a certified
technician should be consulted before performing the operation. Failure to correctly install, remove, or service the
system may result in voiding the warranty, inflicting injury, or even death.

WARNING

The "WARNING" symbol indicates a procedure has a safety risk involved and may cause
death, serious personal injury, or severe product and/or property damage if not
performed safely and within the parameters set forth in this document.

CAUTION

The "CAUTION" symbol indicates a procedure has a safety risk involved and may cause
personal injury or product and/or property damage if not performed safely and within
the parameters set forth in this document.

CAUTION

ELECTRICAL HAZARD. Confirm the battery disconnect switch is in the OFF position before
working on the Firefly Emprise electrical board. Working on an energized board can
cause component damage, short circuits, or personal injury.

Rev: 06.26.2026

Page 1 of 6

Job Code M920031 / TSB

TECHNICAL SERVICE BULLETIN

WATER PUMP CIRCUIT DIODE INSTALLATION

Job Code:

Product:

M920031 – 26-004

Date:

Repair Time:

5/20/2026

Lineage Series VP
0.2 h

Affected Units

Chassis VIN

Serial #

1FDBF6XG4SKA12992 - 1FDBF6XG8SKA12946

TV213BVEE00180 - TV213BVEE00255

Claim Information
Submit warranty claims using the following job code and labor time.
Job Code

M920031

Repair Time

0.2 h

Pre-Auth Required

No

Resources Required
The following tools are required to complete this procedure:
•
•
•

Phillips screwdriver
Wire cutters
Wire strippers

Required Components
Callout

Part #

Qty

A

430007

1

Description
Diode with Wago lever-lock connector (Grand Design RV
supplied)
*Part images not to scale relative to each other.

Rev: 06.26.2026

Page 2 of 6

Job Code M920031 / TSB

TECHNICAL SERVICE BULLETIN

WATER PUMP CIRCUIT DIODE INSTALLATION

Job Code:
Date:

Product:

M920031 – 26-004

Repair Time:

5/20/2026

Lineage Series VP
0.2 h

Preparation
Step 1 — Confirm the battery disconnect switch is in the OFF position.

Instructions
Step 1 — Using a Phillips screwdriver, remove the screw located on the lower right-hand side of the
screen.

Fig. 1 — Screw location — lower right-hand side of the screen.

Rev: 06.26.2026

Page 3 of 6

Job Code M920031 / TSB

TECHNICAL SERVICE BULLETIN

WATER PUMP CIRCUIT DIODE INSTALLATION

Job Code:
Date:

Product:

M920031 – 26-004

Repair Time:

5/20/2026

Lineage Series VP
0.2 h

Step 2 — The screen is hinged on the left. Pull on the right side of the screen to open it and access the
Firefly Emprise electrical board.
Step 3 — Locate the single 14-gauge brown wire connected to the 5-pin connector at the upper center
of the electrical board. Using wire cutters, cut the wire at the location indicated.

Fig. 2 — 14-gauge brown wire at the 5-pin connector — cut location indicated by arrow.

Step 4 — Strip both cut wire ends approximately ¼".
Step 5 — Take the Grand Design RV–supplied diode with the Wago connector and open the locking
levers.

Rev: 06.26.2026

Page 4 of 6

Job Code M920031 / TSB

TECHNICAL SERVICE BULLETIN

WATER PUMP CIRCUIT DIODE INSTALLATION

Job Code:
Date:

Product:

M920031 – 26-004

Repair Time:

5/20/2026

Lineage Series VP
0.2 h

Fig. 3 — Supplied diode with Wago connector — locking levers open.

Step 6 — Insert one stripped wire end into each end of the Wago connector, then close the locking
levers.
NOTE

Diode orientation is critical. The line marked on the diode must face AWAY from the
Firefly electrical board. Installing the diode backwards will prevent the water pump
from operating.

Rev: 06.26.2026

Page 5 of 6

Job Code M920031 / TSB

TECHNICAL SERVICE BULLETIN

WATER PUMP CIRCUIT DIODE INSTALLATION

Job Code:
Date:

Product:

M920031 – 26-004

Repair Time:

5/20/2026

Lineage Series VP
0.2 h

Fig. 4 — Diode installed — marked line facing away from the Firefly board.

Step 7 — Close the screen door and reinstall the screw on the lower right-hand side.
Step 8 — Restore power to the system.

Verification
Before returning the unit to service, verify the following:
•
•
•
•

The diode is fully seated in the Wago connector with both locking levers closed.
The marked line on the diode faces away from the Firefly electrical board.
The screen door is closed and the lower right-hand screw is reinstalled.
The water pump operates correctly with system power restored.

NOTE

Rev: 06.26.2026

If the water pump does not operate after the repair, confirm the diode is installed in the
correct orientation (marked line facing away from the Firefly board).

Page 6 of 6

Job Code M920031 / TSB