DURAMAX-P0689 serious Duramax ›

ECM/PCM Power Relay Sense Circuit Low

The DURAMAX-P0689 (Duramax) diesel fault code means: ECM/PCM Power Relay Sense Circuit Low. This is a serious severity code.

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Keep driving?
Yes, with caution
DIY difficulty
intermediate
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What Are the Symptoms of DURAMAX-P0689?

  • Check Engine Light on
  • Possible no start, stalling or the engine computer staying awake after shut-off

What Causes DURAMAX-P0689? (Most Likely First)

  • Failing power relay High
  • Loose, corroded or damaged relay socket or wiring High
  • Weak battery or poor ground Moderate
  • Engine computer fault Low

Can I Still Drive with DURAMAX-P0689?

Yes, with caution. DURAMAX-P0689 is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.

Frequently Asked Questions

What does P0689 mean on a Duramax?

P0689 means ECM/PCM Power Relay Sense Circuit Low. The engine computer monitors the output of its power relay and is seeing a voltage lower than expected on that sense circuit.

Is P0689 a Duramax-specific code?

No. P0689 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions GM uses to set it on its diesels are in GM service information.

Mechanics Guide Step-by-step diagnosis

How Do You Diagnose DURAMAX-P0689?

  1. Check battery condition and the main grounds first.

  2. Inspect the power relay, its socket and fuses.

  3. Check the relay sense circuit voltage against the service specification.

Sources 1

This page is built from documented references. Verify against your own service info before repair work.

  • SAE J2012Diagnostic Trouble Code Definitions (defines P0689 as a generic OBD-II code)

P0689 on Other Platforms

The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:

Gas / Automotive (OBD-II) Generic OBD-II definition for P0689

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More Duramax codes → Diesel home All diesel codes Heavy-duty Guides

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