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
Estimated cost
$50-$350
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What Are the Symptoms of DURAMAX-P0689?

  • Check Engine Light illuminated
  • Performance loss or rough running (if engine-related)
  • Warning message on dash (DPF/DEF-related)
  • Limp mode under certain conditions
  • Possible hard starting or stalling

What Causes DURAMAX-P0689? (Most Likely First)

  • PCM main relay sense shorted low Very Likely
  • Wiring harness abrasion / connector corrosion Likely
  • Sensor end-of-life (high-mileage trucks) Possible
  • Related upstream fault (e.g., low battery voltage, ground fault) Possible

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 is P0689 on a Duramax?

Duramax code P0689 (ECM/PCM Power Relay Sense Circuit Low) is a serious-severity diagnostic trouble code triggered by the engine control module when it detects a problem in the associated system. Duramax trucks accumulate soft-fault codes — clear them and retest rather than throwing parts at recurring-but-harmless DTCs.

Is a Duramax P0689 safe to drive?

Depends on severity. Critical codes (fuel pressure, PCM, overtemp) need immediate attention. Sensor codes are usually OK short-term.

How much does it cost to fix P0689 on a Duramax?

Estimated repair cost $50-$350. Scan first — cascaded codes often share a single root cause.

Mechanics Guide Step-by-step diagnosis

How Do You Diagnose DURAMAX-P0689?

  1. Scan all modules — a single failure often sets codes in multiple modules

  2. Capture freeze frame and compare to known operating ranges

  3. Back-probe the associated sensor/actuator with a DMM

  4. Inspect wiring and connectors at both ends of the affected circuit

  5. Clear code, perform a complete drive cycle, and verify the fault is fixed

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

Which Vehicles Commonly Get DURAMAX-P0689?

  • 2001-2004 Chevy Silverado 2500/3500 HD 6.6L Duramax LB7
  • 2001-2004 GMC Sierra 2500/3500 HD 6.6L Duramax LB7
  • 2004.5-2005 Chevy Silverado 2500/3500 HD 6.6L Duramax LLY
  • 2004.5-2005 GMC Sierra 2500/3500 HD 6.6L Duramax LLY
  • 2006-2007 Chevy Silverado 2500/3500 HD 6.6L Duramax LBZ
  • 2006-2007 GMC Sierra 2500/3500 HD 6.6L Duramax LBZ
  • 2007.5-2010 Chevy Silverado 2500/3500 HD 6.6L Duramax LMM
  • 2007.5-2010 GMC Sierra 2500/3500 HD 6.6L Duramax LMM
  • 2011-2016 Chevy Silverado 2500/3500 HD 6.6L Duramax LML
  • 2011-2016 GMC Sierra 2500/3500 HD 6.6L Duramax LML
  • 2017+ Chevy Silverado 2500/3500 HD 6.6L Duramax L5P
  • 2017+ GMC Sierra 2500/3500 HD 6.6L Duramax L5P

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