OBD-I Codes List

GM 16 System Voltage Too Low

Make
GM (1982-1995)
Category
Powertrain - Computer and Auxiliary Controls
Severity
Check Engine Light

How to read it

Code 16 reads as 1 flash, pause, 6 flashes on the check-engine light. Jump terminals A and B on the ALDL connector with the key off, then turn the key on with the engine off and count the check-engine flashes.

New to flash codes? The How to Read GM OBD-I Codes with a Paperclip walks through the test and what the numbers mean. The general OBD-I guide covers the rest.

What does GM code 16 mean?

System Voltage Too Low

Common causes of 16

  • Weak battery or failing alternator with low charging voltage
  • Loose or corroded battery cables and engine grounds
  • Worn alternator belt slipping under load
  • On DIS models a direct ignition system circuit fault setting the same code

How to fix 16

  1. Measure battery voltage and charging voltage under load with a meter
  2. Clean and tighten battery terminals and engine ground straps
  3. Test alternator output before replacing any ignition parts
  4. On DIS models check ignition module power and ground feeds
  5. Clear the code and retest after the charging system holds steady voltage

Source

Qualified source review

Sources and review

Review: qualified. Read the source limits below.

  • GM and Chevrolet OBD1 Trouble Codes (ALDL Fault Code List)

    live reference page (troublecodes.net)

    Supports: code identity and GM meaning

    Fetched directly. Single publisher, so the record is qualified, not verified. Causes and check order are curator-written from the circuit the code names.

    https://www.troublecodes.net/gm/

Last updated 2026-09-19.

Report a correction for 16. Include your vehicle, the issue and a source if you have one.

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