P0690 — ECM/PCM Power Relay Sense Circuit High

P0690 — ECM/PCM Power Relay Sense Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit, control module driver fault.

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P0690 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ECM/PCM power relay sense for damage, corrosion, chafing or poor contact.
Subsystem check With the ECM/PCM power relay sense disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P0690 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P0690 (parts and labor, USD, independent shop rates): Control module repair: $300–$1,000; Replace the faulty sensor or actuator: $150–$500; Repair wiring or connectors: $80–$250. Overall, fixing P0690 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of P0690?

Drivers most often notice: the affected system operates intermittently or not at all, Check Engine Light on, increased fuel consumption in some cases, possible limp mode depending on the affected component.

What does OBD2 code P0690 mean?

What is the most common cause of P0690?

The most common causes are: faulty sensor or actuator of the affected circuit, open or shorted wiring in the circuit, control module driver fault.

How much does it cost to fix P0690?

Control module repair — $300–$1,000; Replace the faulty sensor or actuator — $150–$500; Repair wiring or connectors — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will P0690 clear itself?

Sometimes P0690 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

When your vehicle's computer detects an abnormal voltage condition on the engine control module's power relay sense circuit, it logs OBD2 code P0690. This specific fault falls under the powertrain category, meaning it directly relates to engine or transmission operation. The official definition describes this as an "ECM/PCM Power Relay Sense Circuit High" condition.

The powertrain control module constantly monitors the relay that supplies power to critical vehicle systems. Under normal circumstances, the sense circuit carries a specific voltage range that tells the computer whether the relay is engaged and functioning properly. When something forces that circuit to read much higher than intended—typically near full battery voltage—the module recognizes the discrepancy and sets P0690. This doesn't happen from a single bad reading; the fault must repeat under specific operating conditions before the check engine light illuminates and the code becomes permanent.

The ECM captures freeze frame data alongside the fault, recording engine load, RPM, coolant temperature, and vehicle speed at the exact moment the problem occurred. This snapshot becomes your roadmap for diagnosis. When you can replicate those exact operating conditions during testing, you dramatically improve your chances of catching the intermittent fault.

Symptoms of P0690

The Check Engine Light remains illuminated on the dashboard
Systems controlled through the affected relay may operate erratically or stop working entirely
Fuel economy may decrease noticeably compared to normal driving
The vehicle could enter reduced-power limp mode depending on which relay circuit is affected
Starting difficulties or unexpected stalling may occur in severe cases
Auxiliary electrical systems may become non-functional
In rare instances, multiple unrelated codes may appear alongside P0690

Common Causes

The signal wire between the relay and control module has shorted directly to battery positive voltage
An open or failed ground return path prevents proper circuit operation
The ECM/PCM internal driver circuitry has failed, pulling the sense circuit high
Corrosion, moisture intrusion, or mechanical damage at the connector causes erratic signaling
A fuse feeding the relay circuit has blown from an overload or short
Wiring insulation has chafed or melted, allowing the signal wire to contact power sources
The power relay itself has failed internally and sends incorrect status to the computer
Loose terminal connections create intermittent high-resistance paths in the circuit

How to Diagnose P0690

Begin by connecting a quality OBD2 scanner and confirming P0690 is stored in the ECU memory. Before clearing anything, record all freeze frame data—this information reveals precisely what conditions triggered the fault. Review any additional trouble codes present, as related codes often point toward the actual root cause rather than just the symptom.

Consult manufacturer technical service bulletins relevant to your specific make and model. Many P0xxx codes have documented factory fixes, updated software calibrations, or known component weaknesses. Search the NHTSA database or your manufacturer's website using your VIN to find applicable bulletins.

Perform a thorough visual inspection of the wiring harness and connectors in the ECM/PCM power relay circuit. Look for damaged insulation, corroded pins, bent terminals, or any signs of moisture contamination. These defects frequently cause the exact high-voltage conditions this code detects.

With the affected component disconnected from its harness connector, use a multimeter to measure voltage on the signal circuit. If you still read battery-level voltage with the component unplugged, the harness itself contains a direct short to power. If the voltage drops to normal range with the component disconnected, the fault lies within that component's internal circuitry.

Check reference voltage supply, chassis ground integrity, and signal circuit continuity at the connector. Verify all grounds related to the ECM and relay circuit are secure and free of corrosion. Use a wiggle test on the harness while monitoring live data—if the signal drops out or fluctuates, you've found a broken wire or loose connection inside the insulation.

After repairs, clear the code and complete a full drive cycle that reproduces the freeze frame conditions. The fault should not return if the underlying problem was properly identified and corrected.

Repair Options and Costs

Depending on which component fails, repair costs vary significantly. Wiring harness repair or connector replacement typically runs between $80 and $250 including labor and materials. If the sensor or actuator controlled by the relay has failed, expect to pay $150 to $500 for the part and its installation. When the ECM or PCM itself requires internal repair or replacement, costs jump to $300–$1,000.

In most cases, addressing P0690 costs between $80 and $1,000 total. Simple wiring repairs at the lower end of that range resolve the majority of cases. Control module replacement represents the least common scenario, so proper diagnosis before purchasing expensive components always makes financial sense.

Can You Drive with P0690?

Most vehicles remain driveable when this code is present, though you may notice reduced performance or certain electrical systems behaving unexpectedly. The auxiliary system controlled by the faulty relay might not function properly. However, if the fault causes stalling, prevents the engine from starting, or triggers warnings related to braking or steering systems, treat the situation as urgent and seek repairs immediately. Ignoring severe symptoms risks stranding you or creating a safety hazard.