What does P1643 mean on a Ford?

P1643. Fuel Pump Monitor Circuit Low Input. Applies to F-150, Explorer, Expedition.

What causes P1643 on a Ford?

Open monitor circuit Failed monitor sensor Pump not running when commanded Blown pump fuse Corroded connections

How do I fix P1643 on a Ford?

Verify the pump runs when commanded Check the pump fuse Test monitor circuit continuity Inspect connections Replace the sensor after pump confirmation

Code

P1643

Fuel Pump Monitor Circuit Low Input

Category: Powertrain - Fuel/Air Metering
Severity: Check Engine Light
Applies to: F-150, Explorer, Expedition
Related: P0230 Fuel Pump Primary Circuit on OBD Codes List

Findings, check these first

Open monitor circuit
Failed monitor sensor
Pump not running when commanded
Blown pump fuse
Corroded connections

Standard procedure

Verify the pump runs when commanded
Check the pump fuse
Test monitor circuit continuity
Inspect connections
Replace the sensor after pump confirmation

Code lookup

Type a code above, or start from a symptom or a common code.

Press / to jump to the box. Ford-enhanced powertrain, body, chassis and network codes. Generic P0xxx codes live on OBD Codes List.

Sources and review

Review: checked against the recorded source material.

OBDII.pro: P1643 Ford definition
live reference page (obdii.pro)
Supports: Ford-family meaning for P1643: Fuel Pump Monitor Circuit Low Input
Fetched directly. obdii.pro is a publisher independent of the engine-codes family.
P1643 FORD Code: Meaning, Causes, and Symptoms | OBD2 Codes
live reference page (obd2-codes.co)
Supports: Ford meaning for P1643: Fuel Pump Monitor Circuit Low Input
Fetched directly. obd2-codes.co phrasing matches the engine-codes family, so it counts as one publisher.

Last updated 2026-09-06.

Report a correction for P1643. Include your vehicle, the issue and a source if you have one.