OBD-I Codes List

GM 71 A/C Evaporator Temp Sensor Circuit Low Temp Indicated

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

How to read it

Code 71 reads as 7 flashes, pause, 1 flash 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 71 mean?

A/C Evaporator Temp Sensor Circuit Low Temp Indicated

Common causes of 71

  • Failed evaporator temp sensor
  • Shorted sensor wiring
  • Iced evaporator from low charge
  • Faulty sensor connector

How to fix 71

  1. Read codes with an ALDL scan tool
  2. Inspect the sensor connector under the dash
  3. Test sensor resistance and compare with a temp chart
  4. Check for icing on the evaporator case
  5. Check refrigerant charge if icing recurs
  6. Replace the sensor if resistance is out of range

Source

Qualified source review

Sources and review

Review: qualified. Read the source limits below.

  • GM OBD1 trouble codes, model and year page

    live reference page (troublecodes.net)

    Supports: code identity and GM meaning

    Fetched directly from the linked model page. Single publisher, so the record is qualified, not verified.

    https://www.troublecodes.net/GM/91_49B/

Last updated 2026-09-19.

Report a correction for 71. Include your vehicle, the issue and a source if you have one.

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