P0689 — ECM/PCM Power Relay Sense Circuit Low #

Note: The code description for P0689 may vary slightly depending on the vehicle manufacturer (OEM). Always refer to your service manual for the most accurate terminology.

• P0689 – Powertrain Control Module (PCM) Relay Sense Circuit Low (General Motors, Ford, Chrysler, Honda, Nissan, Hyundai)
• P0689 – Engine Control Module (ECM) Power Relay Sense Circuit Low (Toyota, Subaru, Volkswagen, Audi)
• P0689 – ECM/PCM Power Relay Feedback Circuit Low (Mazda, Kia)

Summary of Code P0689 #

The P0689 diagnostic trouble code (DTC) means the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a low voltage signal from the power relay sense circuit. The ECM/PCM is essentially your vehicle’s computerized brain, managing fuel injection, ignition timing, emissions, and more. The power relay is an electronic switch that allows power to reach the ECM/PCM only when needed, safeguarding against battery drain and electrical faults. If the sense circuit voltage is too low, the computer suspects the relay may not be supplying reliable power, threatening critical engine management functions. This code is typically triggered by an electrical issue with the relay, its wiring, or the control module itself.

Common Symptoms for Code P0689 #

When P0689 is set, your vehicle may exhibit a range of symptoms—some subtle, others more disruptive. The severity depends on whether the ECM/PCM is intermittently losing power or operating in a limp mode (a protective strategy to prevent engine damage). Here’s what you might notice:

• Engine may not start or has difficulty starting
• Intermittent stalling (engine shuts off unexpectedly)
• Check Engine Light (CEL) illuminated
• Reduced engine performance (limp mode)
• Other electrical issues (e.g., unresponsive dashboard, sudden loss of power accessories)

Probable Causes for Code P0689 #

Several potential problems can trigger code P0689, but some are far more common than others. Here’s the most likely culprits, in order of frequency:

1. Faulty power relay (relay stuck open or providing poor contact)
2. Wiring issues (corroded, damaged, or loose wires/connectors in the relay sense circuit)
3. Blown fuse (protecting the relay or ECM/PCM circuit)
4. Faulty ECM/PCM (rare, but possible if all else checks out)
5. Low battery voltage (causing insufficient relay operation)

Step-by-Step Diagnostic for Code P0689 #

A methodical diagnosis is essential to avoid unnecessary parts replacement. Here’s a proven approach used by professional technicians:

1. Verify the code with a scan tool and check for related DTCs.
2. Inspect the battery and charging system for proper voltage (at least 12.6V with engine off).
3. Locate the ECM/PCM power relay (refer to vehicle-specific diagrams, usually in the fuse/relay box).
4. Check relay operation by swapping with a known good relay (if identical relays are available).
5. Test the relay sense circuit for continuity and voltage using a multimeter.
6. Inspect wiring and connectors for corrosion, looseness, or damage between the relay, ECM/PCM, and battery.
7. Check related fuses for continuity and proper amperage.
8. Clear the code and test drive to see if it returns.
9. If the problem persists, test the ECM/PCM power and ground circuits; replace the module only if all other causes are eliminated.

Possible Repairs for Code P0689 #

Once you’ve identified the root cause, the following repairs are typically effective:

• Replace a faulty ECM/PCM power relay
• Repair or replace damaged wiring or connectors in the relay sense circuit
• Replace any blown fuses associated with the ECM/PCM or relay circuit
• Clean corroded terminals at relay or module connectors
• Recharge or replace the battery if voltage is low
• Replace the ECM/PCM (only if definitively proven faulty, which is rare)

Is It Safe to Drive with Code P0689? #

Driving with code P0689 is generally not recommended. While your vehicle may sometimes start and run, the code indicates that the brain of your car (the ECM/PCM) may intermittently lose power. This can lead to sudden stalling, loss of essential functions, or the inability to restart the engine. For safety and reliability, resolve this issue promptly before regular driving.

Vehicles Most Commonly Affected by Code P0689 #

P0689 is a generic OBD-II code, but it’s more frequently reported on certain makes and models, especially those using specific relay designs or known for relay/wiring issues. Some commonly affected vehicles include:

• Chevrolet (Malibu, Equinox, Cruze, Silverado)
• Ford (F-150, Focus, Escape, Fusion)
• Chrysler/Dodge/Jeep (Town & Country, Grand Caravan, Ram, Grand Cherokee)
• Honda (Accord, Civic, CR-V)
• Nissan (Altima, Sentra, Rogue)
• Hyundai/Kia (Sonata, Elantra, Sorento)
• Toyota/Subaru (Camry, Corolla, Outback, Forester)

Common Mistakes & Best Practices for Code P0689 #

A few pitfalls trip up even seasoned DIYers and technicians. Here’s what to watch out for and how to get it right:

• Replacing the ECM/PCM prematurely (always test relay, wiring, and fuses first)
• Overlooking simple wiring faults (corrosion or loose connectors can mimic complex issues)
• Ignoring battery health (low voltage can trigger a cascade of false codes)
• Skipping the basics—always verify power and ground before suspecting modules
• Not consulting OEM wiring diagrams for correct relay pin identification

Quick FAQ for Code P0689 #

Here are some fast answers to common concerns about P0689:

• Q: Can a bad battery cause P0689?
  A: Yes—if the battery is weak or the charging system has issues, the ECM/PCM relay may not function correctly, triggering this code.
• Q: Is it expensive to fix P0689?
  A: In most cases, no. Power relays and basic wiring repairs are affordable. Only if the control module is at fault does the cost rise significantly.
• Q: Will clearing the code with a scanner fix the problem?
  A: No—while the code may disappear temporarily, it will return unless the underlying electrical issue is resolved.