What does P1550 mean on a Chevy?

P1550. Fuel Injector Control Module System Voltage. Applies to Silverado 2500HD, Sierra 2500HD Duramax Diesel.

What causes P1550 on a Chevy?

High resistance in the FICM power or ground circuits from corroded terminals Weak batteries or charging system starving the FICM on crank Failing fuel injector control module with internal voltage fault Chafed FICM harness near the alternator bracket on LLY engines

How do I fix P1550 on a Chevy?

Load-test both batteries and the charging system before touching the FICM Probe FICM power and ground circuits with a DMM for voltage above 10 volts Inspect FICM connectors for fretting corrosion and terminal spread Rule out U0073 and U0105 communication codes first per the diagnostic table Replace the FICM only on confirmed low supply voltage with good feeds and grounds

Code

P1550

Fuel Injector Control Module System Voltage

Category: Powertrain - Computer and Auxiliary Controls
Severity: Check Engine Light
Applies to: Silverado 2500HD, Sierra 2500HD Duramax Diesel
Related: No single generic twin. See OBD Codes List

What it means

P1550. Fuel Injector Control Module System Voltage. This Chevy-enhanced code applies to Silverado 2500HD, Sierra 2500HD Duramax Diesel.

Findings, check these first

High resistance in the FICM power or ground circuits from corroded terminals
Weak batteries or charging system starving the FICM on crank
Failing fuel injector control module with internal voltage fault
Chafed FICM harness near the alternator bracket on LLY engines

Standard procedure

Load-test both batteries and the charging system before touching the FICM
Probe FICM power and ground circuits with a DMM for voltage above 10 volts
Inspect FICM connectors for fretting corrosion and terminal spread
Rule out U0073 and U0105 communication codes first per the diagnostic table
Replace the FICM only on confirmed low supply voltage with good feeds and grounds

Look up another code

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Sources and review

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Last updated 2026-09-19.

Report a correction for P1550. Include your vehicle, the issue and a source if you have one.

This fault is part of the Chevy P1xxx fuel and ignition codes guide. It covers the family and the order to check it.