OBD-II Fault Code

P1642: Fuel Pump Monitor Circuit High Input

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P1642.

System family

Powertrain

Manufacturer-specific

Repair category

Fuel system

Use this category to narrow your checks before replacing parts.

Severity

High

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What P1642 usually means

Fuel Pump Monitor Circuit High Input.

Common symptoms

Check Engine light; Poor drivability or reduced fuel economy depending on fault; Hard start, hesitation, stalling or inaccurate fuel reading depending on component

Likely causes

Low fuel pressure; Faulty pump/regulator/sensor; Wiring fault; Clogged filter; Injector fault; High signal voltage; Open ground; Short to voltage; Failed sensor

Diagnostic checks

Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Check fuel pressure and sensor data; Inspect pump/injector fuses, relay, wiring and grounds; Check sensor ground and signal circuit for short to voltage

Repair guidance

Repair wiring/relay issues, replace clogged filter, failed pump/sensor/injector only after testing; Repair ground/signal circuit or replace confirmed faulty sensor

Verification after repair

Clear code, road-test through the same drive condition, then rescan

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary; Manufacturer-specific: confirm definition and test steps in the vehicle service manual. A DTC identifies a circuit or system condition, not always the failed part.