OBD-I Codes List

GM 26 Quad Driver Module A Error

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

How to read it

Code 26 reads as 2 flashes, 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 26 mean?

Quad Driver Module A Error

Common causes of 26

  • Shorted solenoid or relay on a quad driver output circuit
  • Failed EVAP canister purge or EGR solenoid pulling the driver down
  • Damaged wiring shorted to ground or power
  • Internal ECM quad driver fault

How to fix 26

  1. Note which output device stopped working such as the purge solenoid or fan relay
  2. Disconnect output devices one at a time and recheck the code
  3. Test each solenoid and relay coil resistance against specification
  4. Inspect harness branches for shorts to ground
  5. Replace the ECM only after every output circuit tests good

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

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