P0690 — ECM/PCM Power Relay Sense Circuit High #

Note: The code label may vary depending on the vehicle manufacturer.

• ECM/PCM Power Relay Sense Circuit High (Generic)
• Engine Control Module Power Relay Sense Circuit High (Honda, Toyota, Nissan, GM)
• PCM Power Relay Sense Circuit High Input (Ford, Chrysler)

Summary of Code P0690 #

The P0690 diagnostic trouble code (DTC) indicates that the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an abnormally high voltage in the power relay sense circuit. This circuit monitors the status of the relay responsible for supplying power to the ECM/PCM, ensuring the computer is energized when the ignition is on. When the voltage signal in this sense circuit is unexpectedly high, the ECM/PCM assumes there is a fault in the relay, wiring, or related components. While this code is not among the most common, it can cause significant drivability issues if left unresolved.

Understanding and addressing this code promptly is crucial, as the ECM/PCM is the “brain” of your vehicle, controlling everything from fuel injection to emission systems. If its power supply is unreliable, your vehicle could experience anything from minor glitches to total no-start conditions.

Common Symptoms for Code P0690 #

When P0690 is present, symptoms can range from subtle to severe, depending on the nature and duration of the fault. Because the ECM/PCM relies on a steady power supply, any disruption in this sense circuit can cause unpredictable behavior. Drivers may notice:

• Check Engine Light illuminated on the dashboard
• Engine may not start or may stall unexpectedly
• Reduced engine performance or limp mode
• Intermittent electrical issues (e.g., flickering lights, erratic gauges)
• Communication errors with scan tools or during reprogramming attempts

Most Likely Causes for Code P0690 #

The P0690 code is generally triggered by electrical faults in the ECM/PCM power relay circuit. Some causes are more common than others, and understanding the hierarchy of possibilities can save time during diagnosis:

1. Failed ECM/PCM power relay — The relay itself can fail mechanically or electrically, causing a high signal.
2. Wiring issues — Damaged, corroded, or shorted wiring in the relay sense circuit is a frequent culprit.
3. Loose or corroded connectors — Connectors at the relay, fuse box, or ECM/PCM can develop high resistance.
4. Faulty ECM/PCM (rare) — In some cases, the module’s internal circuitry may fail to interpret the sense signal correctly.
5. Aftermarket modifications — Non-OEM remote start systems or alarm installations may interfere with the relay circuit.

Step-by-Step Diagnosis for Code P0690 #

Diagnosing P0690 requires a methodical approach to rule out the most common issues before considering rare failures like a defective ECM/PCM. Here is a typical troubleshooting path:

1. Verify the code with a professional-grade scan tool and check for additional faults.
2. Consult the OEM wiring diagram for the exact layout of the power relay sense circuit for your vehicle.
3. Visually inspect the ECM/PCM power relay and associated fuse(s) for signs of overheating, corrosion, or looseness.
4. Test relay operation by swapping it with a known good relay (if identical) or using a relay tester.
5. Check wiring continuity and resistance in the sense circuit with a multimeter, looking for opens, shorts to ground, or high resistance.
6. Inspect connectors at the relay, fuse box, and ECM/PCM for bent pins, corrosion, or loose fit.
7. Test ECM/PCM power and ground circuits to ensure the computer is receiving correct voltages.
8. If all else tests good, suspect a faulty ECM/PCM (rare; consult OEM service information before replacement).

Possible Repairs for Code P0690 #

Once the root cause is identified, repairs should be made with attention to detail and quality. Here are solutions matched to the most common causes:

• Replace the ECM/PCM power relay if found faulty during testing.
• Repair or replace damaged wiring in the relay sense circuit, ensuring all splices are properly sealed and routed.
• Clean or replace corroded connectors to restore proper electrical contact.
• Reinstall or repair loose fuse box terminals or relay sockets.
• Remove or properly integrate aftermarket alarm/remote start wiring interfering with the circuit.
• Replace the ECM/PCM only if thoroughly verified as the cause, and always perform module programming as required by the OEM.

Is It Safe to Drive with Code P0690? #

Limited. While the vehicle may operate with P0690 stored, continued driving is not recommended until the cause is addressed. The underlying issue could lead to sudden engine stalling or a no-start situation, potentially leaving you stranded. If you notice any drivability problems or repeated no-starts, have the vehicle inspected and repaired as soon as possible.

Vehicles Most Commonly Affected by Code P0690 #

P0690 can appear in a wide range of modern vehicles, but it is more frequently reported in certain makes and models, particularly those with sensitive relay monitoring systems. Notably:

• Honda (Accord, Civic, CR-V)
• Toyota (Camry, Corolla, RAV4)
• Nissan (Altima, Sentra, Rogue)
• Chevrolet (Malibu, Cruze, Equinox)
• Ford (Focus, Fusion, Escape)
• Chrysler/Dodge (Journey, Charger, Caravan)

Other manufacturers can also be affected, especially as more vehicles implement advanced relay monitoring in their control architectures.

Common Mistakes & Best Practices for Code P0690 #

Avoiding missteps during diagnosis and repair can save time and prevent unnecessary expenses. Technicians and DIYers should keep these points in mind:

• Ignoring basic checks — Always start with the relay and wiring before assuming the ECM/PCM is faulty.
• Overlooking aftermarket wiring — Alarm or remote start systems frequently cause intermittent relay circuit faults.
• Not consulting OEM diagrams — The relay sense circuit can vary significantly between models; always refer to the specific wiring diagram.
• Skipping continuity tests — Visual inspection is not enough; use a multimeter to verify circuit integrity.
• Replacing the ECM/PCM prematurely — Module failure is rare and should only be considered after all other options are exhausted.

Express FAQ for Code P0690 #

As this code can be confusing, here are quick answers to common questions:

• Q: Can a bad battery cause P0690?
  A: While a weak battery can cause various electrical issues, P0690 specifically points to relay circuit problems. However, if low voltage causes relay chatter or intermittent power, it might indirectly contribute.
• Q: Does P0690 mean my ECM/PCM is bad?
  A: Not necessarily. Most often, the issue is with the relay, wiring, or connectors. Only consider module replacement if all other components test good.
• Q: Is it expensive to fix P0690?
  A: Costs vary. Replacing a relay or repairing wiring is usually affordable, while ECM/PCM replacement and programming can be significantly more expensive.