P0690
UniversalThe Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a voltage signal from its power relay sense circuit that is higher than the specified limit.
High SeverityThis code indicates that the Engine Control Module (ECM) or Powertrain Control Module (PCM) is receiving an unexpectedly high voltage signal from its main power relay. This electrical fault can prevent the vehicle from starting or cause the engine to stall unexpectedly.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before inspecting or working on any electrical components to prevent electrical shock or damage to the vehicle's electrical system. Be cautious of hot engine components and moving parts when working under the hood. Consult a professional if you are unsure about any diagnostic or repair steps.
Common Symptoms
- Check Engine Light illuminated
- Engine cranks but does not start
- Engine stalls unexpectedly
- Intermittent loss of engine power
- Vehicle runs rough
- Engine may not start at all
Common Causes
- Faulty ECM/PCM power relay
- Short to voltage in the power relay sense circuit wiring
- Corroded or loose electrical connections at the relay or PCM
- Internal fault within the ECM/PCM (less common)
Frequently reported on: All Makes
Diagnostic Steps
- Check all fuses related to the ECM/PCM and main power supply. Replace any blown fuses.
- Locate the ECM/PCM power relay. Often, there will be a diagram on the fuse box cover. Remove and inspect the relay for any signs of damage or corrosion.
- If possible, swap the ECM/PCM power relay with a known good, identical relay from another non-critical system (e.g., horn relay) to test if the relay is faulty.
- Visually inspect the wiring harness leading to the ECM/PCM power relay and the PCM itself for any obvious signs of damage, fraying, or shorting to positive voltage.
- Clear the P0690 code and test drive the vehicle if it's able to run. If the code returns, further electrical diagnosis with a multimeter may be required.
👨🔧 When to Call a Professional
If after checking basic fuses and relay connections the issue persists, or if the vehicle experiences intermittent stalling or no-start conditions, it is highly recommended to consult a professional automotive technician. Diagnosing complex electrical issues, especially those involving the PCM, often requires specialized tools and expertise.
Commonly Asked Questions
What exactly does the P0690 code mean?
The P0690 code signifies that the vehicle's computer (ECM/PCM) has detected a higher-than-normal voltage signal from the circuit that monitors its main power supply relay. This indicates an electrical fault in that specific circuit.
Can I drive my car with a P0690 code?
Driving with a P0690 code is not recommended. The issue could lead to the engine stalling unexpectedly while driving or prevent the vehicle from starting at all, creating a safety hazard.
What are the most common causes for a P0690 code?
The most common causes include a faulty ECM/PCM power relay, a short to voltage in the relay's wiring, or corroded electrical connections affecting the relay or the PCM's power circuit.
How can I test the ECM/PCM power relay?
You can test the relay by checking its continuity with a multimeter, applying power to its coil to see if it clicks, or by swapping it with a known good, identical relay from another non-critical circuit in your vehicle.
Does a P0690 code always mean my PCM is bad?
No, a P0690 code rarely points directly to a bad PCM. It's much more likely to be an issue with the power relay itself, its wiring, or the connections within the circuit. The PCM is usually the last component to suspect after thoroughly checking the relay and wiring.