P1642 Code: Meaning, Symptoms, Causes & Fix

Overview

Code P1642 indicates a fault in Fuel Pump Monitor Circuit High Input, typically within fuel delivery and pressure control.

Symptoms

reduced fuel economy
hesitation under acceleration
engine may stall at idle

Common causes

Disconnected or loose connector affecting fuel pump monitor circuit high input
Broken terminal inside harness
Connector pin damage/corrosion or harness stress near related components

How to diagnose P1642

Confirm P1642 and capture freeze-frame data with a professional scan tool.
Inspect wiring, connectors, and grounds related to fuel pump monitor circuit high input for obvious defects.
Use a continuity test from module pin to component to identify opens/high resistance.
Check for related DTCs to identify the root-cause chain before replacing parts.
After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P1642

Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.

Can you drive with P1642?

Most vehicles can be driven short-term with P1642, but postpone heavy load/highway driving until repaired.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

Repair obvious wiring/connector faults first to prevent repeat parts replacement.
Address the root fault mode (open) in the fuel pump monitor circuit high input circuit/system.
Apply the required relearn/adaptation procedure if specified by service information.
Road-test and verify P1642 remains cleared under the conditions that originally set the code.

Fix options

Clear corrosion and protect terminals.
Repair open circuit and secure connector lock.
Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$220-$1100

Common mistakes when diagnosing P1642

Replacing parts without verifying voltage, ground, and signal integrity first.
Ignoring related stored/pending codes that indicate upstream faults.
Skipping post-repair verification drive cycle and readiness checks.

P1642 in common vehicles

P1642 appears across makes such as Mazda, Subaru, Lexus, Jeep. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P1642?

P1642 is commonly set by open faults affecting fuel pump monitor circuit high input.

How much does it cost to fix P1642?

For P1642, repair costs are typically $220-$1100 depending on exact root cause, labor rates, and part quality.

Can I clear P1642 without repair?

You can clear P1642 temporarily, but the code usually returns until the underlying fault is corrected.