OBD-I Codes List

GM 47 UART Serial Data Circuit Error

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

How to read it

Code 47 reads as 4 flashes, pause, 7 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 47 mean?

UART Serial Data Circuit Error

Common causes of 47

  • Open serial data line between modules
  • Failed body or climate module pulling the line down
  • Corroded ALDL connector data pin
  • Poor module ground shared with the data circuit

How to fix 47

  1. Check whether other modules still communicate through the ALDL port
  2. Inspect the data line wiring for opens and shorts
  3. Disconnect add on modules one at a time and recheck communication
  4. Verify module powers and grounds before replacing a module
  5. Clear the code and confirm data exchange resumes on a scan tool

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 47. Include your vehicle, the issue and a source if you have one.

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