The P0690 trouble code is a diagnostic code related to the powertrain control module (PCM) or engine control module (ECM) power relay circuit. When this code is triggered, it indicates that the vehicle’s computer has detected a high voltage condition in the power relay sense circuit. This issue can lead to various problems with your vehicle’s performance and may even prevent it from starting.

P0690 Code Meaning	P0690 Code Common Causes
ECM/PCM Power Relay Sense Circuit High	Faulty PCM power relay
Voltage exceeds maximum allowable parameter	Damaged or corroded wiring
Issue with PCM power supply	Blown fuse or fusible link
Problem in the control circuit voltage	Defective PCM

Symptoms of P0690 Code

When your vehicle triggers the P0690 code, you may experience several symptoms that can affect your driving experience. Understanding these symptoms can help you identify the issue quickly and take appropriate action. Here are the common symptoms associated with the P0690 error code:

1. Illuminated Check Engine Light: The most obvious sign of a P0690 code is the illumination of the check engine light on your dashboard. This warning light is your vehicle’s way of alerting you to a potential problem that requires attention.
2. Engine Cranking Issues: You may notice that your engine cranks but fails to start. This can be particularly frustrating, especially if you’re in a hurry or in an inconvenient location.
3. No-Start Condition: In some cases, your vehicle may not start at all. This is often due to the PCM not receiving the necessary power to initiate the starting sequence.
4. Intermittent Starting Problems: Your vehicle might start sometimes but fail to start at other times, making the issue seem inconsistent and hard to diagnose.
5. Electrical System Malfunctions: You may experience issues with various electrical components in your vehicle, as the PCM controls many of these systems.
6. Poor Engine Performance: If your vehicle does start, you might notice a decrease in engine performance, including rough idling, hesitation during acceleration, or reduced fuel efficiency.
7. Battery Drain: In some cases, a faulty power relay can cause excessive battery drain, leading to a dead battery if the vehicle is left unused for extended periods.

Understanding these symptoms can help you communicate more effectively with your mechanic and potentially save time in the diagnostic process.

Technical Explanation of P0690 Code

To fully grasp the P0690 code, it’s essential to understand the role of the PCM/ECM power relay and how it interacts with your vehicle’s systems. The PCM, or Powertrain Control Module, is the brain of your vehicle’s engine management system. It requires a constant and stable power supply to function correctly.

The power relay is responsible for supplying this power to the PCM. When you turn the key in the ignition, the power relay is activated, allowing current to flow from the battery to the PCM. The PCM then uses this power to control various engine functions and monitor sensor inputs.

The P0690 code specifically relates to the “sense circuit” of this power relay. This circuit allows the PCM to monitor the status of the relay and ensure it’s functioning correctly. When the code is triggered, it means the PCM has detected a voltage in this sense circuit that is higher than the maximum allowable parameter set by the manufacturer.

This high voltage could be caused by several factors:

1. A faulty relay that’s not switching off properly
2. A short circuit in the wiring that’s causing voltage to leak into the sense circuit
3. A problem with the PCM itself, causing it to misread the voltage

The complexity of this system means that diagnosing the exact cause of a P0690 code often requires specialized diagnostic equipment and a deep understanding of automotive electrical systems.

Step-by-Step Diagnosis of P0690 Code

Diagnosing the P0690 code requires a systematic approach. Here’s a step-by-step guide to help you or your mechanic pinpoint the issue:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. Make note of any additional codes that may be present alongside P0690.
2. Clear the codes and test drive the vehicle to see if the P0690 code returns. If it doesn’t, the issue may be intermittent.
3. If the code returns immediately, begin with a visual inspection of all wiring and connectors related to the PCM and power relay. Look for signs of damage, corrosion, or loose connections.
4. Use a digital multimeter to check the voltage at the PCM power supply pins. Compare the readings to the manufacturer’s specifications.
5. Test the power relay itself. Remove the relay and use the multimeter to check for proper resistance and operation when activated.
6. Inspect all relevant fuses and fusible links. Replace any that are blown or damaged.
7. If all components check out, the issue may lie within the PCM itself. At this point, it’s advisable to seek professional diagnostic services.
8. If a faulty component is identified, replace it and clear the codes. Test drive the vehicle to ensure the problem is resolved.

Remember, this diagnosis requires technical knowledge and specialized tools. If you’re not comfortable performing these steps, it’s best to consult a professional mechanic.

Solution Methods for P0690 Code

Once you’ve diagnosed the root cause of the P0690 code, you can proceed with the appropriate solution. Here are some common fixes:

1. Replace the PCM Power Relay: If the relay is found to be faulty, replacing it is often the simplest solution. Ensure you use a relay that matches the specifications of your vehicle.
2. Repair Wiring Issues: If damaged or corroded wiring is the culprit, repair or replace the affected wiring harness. This may involve soldering connections, replacing connectors, or in some cases, replacing entire sections of the wiring harness.
3. Replace Blown Fuses: If a blown fuse is causing the issue, simply replacing it might solve the problem. However, it’s crucial to identify why the fuse blew in the first place to prevent recurrence.
4. Clean Corroded Connections: Sometimes, simply cleaning corroded battery terminals or ground connections can resolve electrical issues. Use a wire brush and battery terminal cleaner for best results.
5. Reprogram or Replace the PCM: In rare cases where the PCM itself is faulty, it may need to be reprogrammed or replaced. This is a job best left to professionals, as it requires specialized equipment and expertise.

Warning: Always disconnect the battery before working on electrical components to avoid short circuits or electrical shock.

Cost Estimates for P0690 Code Repairs

The cost of repairing a P0690 code can vary widely depending on the root cause and the make and model of your vehicle. Here are some rough estimates:

1. Relay Replacement: $50 – $200
2. Wiring Repair: $100 – $500
3. Fuse Replacement: $5 – $50
4. PCM Reprogramming: $50 – $200
5. PCM Replacement: $500 – $2,000

These estimates include parts and labor. DIY repairs can significantly reduce costs, but remember that misdiagnosis or improper repair can lead to more expensive problems down the line.

Warnings and Recommendations

When dealing with the P0690 code, keep the following in mind:

• Never ignore a check engine light. Continuing to drive with this code active could lead to more severe engine damage.
• If you’re not comfortable with automotive electrical systems, seek professional help. Mishandling electrical components can be dangerous and potentially cause more damage.
• Always use high-quality replacement parts that meet or exceed OEM specifications.
• After repairs, clear the codes and test drive the vehicle to ensure the problem is fully resolved.
• Regular maintenance can prevent many electrical issues. Keep your battery clean and check connections periodically.
  

In conclusion, the P0690 code, while potentially serious, is often resolvable with proper diagnosis and repair. By understanding the symptoms, causes, and solutions associated with this code, you can approach the problem more confidently and make informed decisions about repairs. Remember, when in doubt, consult with a certified mechanic to ensure your vehicle receives the care it needs.

Frequently Asked Questions About P0690

• Can I drive my car with a P0690 code?
  It’s not recommended to drive with this code active. The vehicle may not start or could stall while driving, potentially creating a dangerous situation.
• How urgent is it to fix a P0690 code?
  This code should be addressed as soon as possible. It affects the PCM’s power supply, which is crucial for proper engine operation and could lead to no-start conditions.
• Will a P0690 code clear itself?
  While some codes can clear themselves, P0690 typically won’t clear without fixing the underlying issue. The problem will likely persist until repaired.
• Can a bad battery cause a P0690 code?
  While a bad battery itself doesn’t typically cause this code, it can contribute to electrical system issues that might trigger P0690. Always check the battery’s condition during diagnosis.
• How long does it take to fix a P0690 code?
  Repair time can vary from 1-3 hours for simple relay or fuse replacements to several hours for more complex wiring or PCM issues. Diagnosis time is additional.
• Is P0690 code covered under warranty?
  It depends on your vehicle’s warranty terms and the cause of the issue. Many powertrain warranties would cover PCM-related problems, but always check your specific warranty.
• Can I replace a PCM power relay myself?
  If you’re comfortable with basic automotive repairs, replacing a relay is often straightforward. However, proper diagnosis is crucial to ensure the relay is the actual problem.
• What’s the difference between P0690 and P0691 codes?
  While P0690 indicates a high voltage in the PCM power relay sense circuit, P0691 indicates a low voltage in the same circuit. Both relate to PCM power supply issues but have different causes.