# Service bulletin 26\-004

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

- Type: Service bulletin
- NHTSA id: 11034093
- Published by NHTSA: 2026\-06\-26
- Manufacturer's number: 26\-004
- Manufacturer's date: 2026\-06\-26
- Campaign id or software version: 26\-004
- NHTSA component: ELECTRICAL SYSTEM

## NHTSA's summary

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.

## The document

- [NHTSA's copy of the document (PDF)](https://static.nhtsa.gov/odi/tsbs/2026/MC-11034093-0001.pdf)
- [If that address does not open, try this one](https://static.nhtsa.gov/odi/tsbs/2026/MC-11034093-9999.pdf)

The document is the manufacturer's. This site does not hold it.

## Components

Electrical system

## Vehicles listed

- 2027 GRAND DESIGN LINEAGE

JSON: [/v1/bulletins/11034093](/v1/bulletins/11034093)

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