P0690 — ECM/PCM Power Relay Sense Circuit High

The trouble code P0690 indicates an issue related to the power relay sense circuit within the vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM). Essentially, this code means that the vehicle’s control system detects an abnormally high voltage or signal in the relay sense circuit, which could be caused by electrical or wiring problems. Be aware that labels and terminology may vary slightly between different OEMs, but the underlying issue is generally consistent across makes and models.

Fast Facts

System affected: Electrical/Power Relay Circuit
Severity: Moderate — may affect vehicle operation if unattended
Main symptoms: Malfunction indicator light, starting issues, or electrical faults
Driveability: Limited — depending on severity, vehicle may still operate but with risks

Manufacturer variations for trouble code P0690

Different vehicle manufacturers may assign alternative labels or fault descriptions for the P0690 code. It is essential to identify these variations to ensure accurate diagnosis and repair. Below are some known label variations:

Ford: P0690 may be labelled as “Fuel Pump Control Module Power Relay Sense Circuit High”
BMW: Similar codes may be listed as “Relay Control Circuit High / Open”
Volkswagen / Audi: Known as “Relay Power Supply Circuit – High Voltage”
Other OEMs: Variants such as “Relay Sense Circuit High Voltage” or “ECM Power Relay Circuit Malfunction” may be used

What does trouble code P0690 mean?

In simple terms, this code signals that the **vehicle’s electronic control system** has detected an abnormally high voltage or current in the **power relay sense circuit**. The ECU (Engine Control Unit) constantly monitors various circuits to ensure proper operation. When it perceives that the relay circuit’s voltage level exceeds a predetermined threshold—often due to an electrical overload or short circuit—this code is triggered.

This situation typically arises during the vehicle’s startup, operation, or in response to electrical anomalies. The purpose of the detection is to protect the electrical system from damage and ensure reliable fuel delivery, ignition, or other critical functions managed by relays.

Severity and risks of trouble code P0690

The **severity** of this code can vary depending on the specific vehicle and the system affected. If the circuit malfunction is minor, the vehicle might continue to function normally, but there is an increased risk of electrical shorts, relay failure, or downstream system faults. In more severe cases, critical components like the fuel pump, ignition system, or emissions controls could be affected, leading to reduced performance or stalls.

**Is the vehicle drivable?**

Limited — Yes in some cases, but it is recommended to have a professional diagnosis performed as soon as possible to prevent further damage or breakdowns.

Symptoms of trouble code P0690

Vehicles exhibiting this fault may not always display obvious symptoms initially. However, common signs include:

Check Engine Light (CEL) or Malfunction Indicator Light (MIL) illuminated on the dashboard
Difficulty starting the vehicle or intermittent starting issues
Electrical systems malfunctioning, such as failure of relayed components like fuel pump or cooling fan
Erratic engine behavior or stalls during operation
Unusual noises or smells from electrical or relay components

Most likely causes of trouble code P0690

Understanding the root causes of this fault can help expedite repairs. The causes are generally electrical or wiring-related, but can also involve components within the relay circuit itself.

Faulty relay or relay control module: The relay used to switch power to critical systems may be defective or failing.
Wiring issues: Short circuits, damaged insulation, corrosion, or loose connections in the relay circuit wiring can cause abnormal voltage readings.
High resistance or poor grounding: Insufficient grounding points or corroded connectors can lead to voltage irregularities in the relay sense circuit.
Malfunctioning PCM or ECU: Although less common, an internal fault within the control module can cause incorrect signals or readings.
Electrical overloads or aftermarket modifications: Non-standard wiring, added accessories, or faulty aftermarket components may influence the relay circuit.

How to diagnose trouble code P0690

Diagnosing this fault reliably involves a systematic approach, combining visual inspection with live data analysis and electrical testing. Here’s a generic diagnostic guideline:

Begin with visual inspection: Check wiring harnesses, connectors, and relay components for damage, corrosion, or loose connections.
Using the scan tool, verify live data: Inspect voltage readings in the relay circuit when the vehicle is turned on and compare readings to manufacturer specifications.
Test the relay circuits: Using a multimeter, perform continuity and resistance checks on relays and related wiring.
Perform wiring continuity checks: Trace wiring from the relay to the control module, looking for shorts, opens, or high resistance areas.
Assess ground points: Measure voltage and ensure proper grounding at relevant points, cleaning or tightening connections if needed.
Try swapping relays: If applicable, replace the relay with a known good unit to see if the fault clears or persists.

Possible repairs for trouble code P0690

Repairs depend on the identified root cause but generally involve electrical fixes or component replacements. In most cases, these are DIY-friendly but may require professional intervention if internal circuit or control module issues are suspected.

Replace the relay: A common fix if the relay itself is faulty. This is a basic repair, often straightforward.
Repair or replace wiring harness: Fix damaged wiring, replace corroded connectors, or re-seat loose connections. Usually a basic repair.
Secure grounds and clean contact points: Ensuring proper grounding can effectively address high circuit resistance. Basic task.
Upgrade or replace the control module: If internal faults within the ECU or PCM are confirmed, professional replacement or reprogramming is required.
Avoid aftermarket wiring complications: Remove or rectify unauthorized modifications that interfere with OEM wiring.

Vehicles commonly associated with trouble code P0690 in Europe

This fault is frequently encountered across a broad range of vehicles, particularly those with complex electrical systems. While specific data can vary, typical affected brands include:

Ford: Focus, Fiesta, Mondeo

BMW: 3 Series, 5 Series

Volkswagen / Audi: Golf, Passat, A3

Mercedes-Benz: C-Class, E-Class

Peugeot / Citroën / Renault: Various models with complex relay circuits

Frequent mistakes with trouble code P0690

Diagnosing and repairing this fault requires precision. Common errors include:

Overlooking visual inspection: Jumping straight to electronic testing without inspecting wiring and connectors can miss obvious faults.
Replacing relays without testing: Changing relays blindly may not address the underlying issue, leading to repeated faults.
Ignoring grounding issues: Poor grounds are a frequent cause that is often overlooked by technicians.
Confusing related codes: Failing to differentiate between similar relay or circuit fault codes can lead to incorrect repairs.

FAQ — trouble code P0690

Can this code disappear on its own? While minor electrical issues might resolve temporarily, persistent high voltage signals typically require repair. Relying on a code to clear without fixing the root cause can lead to further problems.

Can I keep driving? It depends. If the vehicle is still running normally without symptoms, it may be safe temporarily. However, driving with electrical faults risks damage to components and is generally not advised. A professional diagnosis is recommended.

Why does the code return after clearing? Because the underlying electrical problem remains unresolved—such as a wiring fault, relay failure, or bad ground—the code will reappear once the ECU performs its diagnostic checks again.