P1569 - Cruise Servo Stroke High While not in Cruise

The diagnostic trouble code (DTC) P1569 indicates a problem with the cruise control system. Specifically, it signals that the cruise control servo stroke is registering as being higher than expected when the cruise control system is not actively engaged. This can result in the cruise control system failing to function correctly, or even causing unintended acceleration. Addressing this code promptly is crucial for maintaining vehicle safety and preventing potential accidents.

P1569: Understanding the Code

The following table provides a detailed breakdown of the P1569 code, including potential causes, symptoms, and diagnostic steps.

Detailed Explanations

Code Definition: Cruise Servo Stroke High While not in Cruise

This code signifies that the cruise control servo, the device responsible for adjusting the throttle to maintain a set speed, is registering a stroke position that is higher than expected when the cruise control system is not actively engaged. This means the servo is attempting to open the throttle even when the cruise control is off, which is a malfunction.

Symptoms

• Cruise control inoperative or intermittent: The most common symptom is the cruise control simply not working or working sporadically. It might fail to engage, disengage unexpectedly, or have difficulty maintaining a consistent speed.
• Unintended acceleration (rare): While rare, a high servo stroke when the cruise control is off can potentially cause the vehicle to accelerate without driver input. This is a serious safety concern.
• Cruise control light flashing or not illuminating: The cruise control indicator light on the dashboard might flash, remain off entirely, or behave erratically, indicating a problem within the system.
• Engine surging or fluctuating RPM: The engine RPM might fluctuate or surge even when the vehicle is stationary or being driven at a constant speed, suggesting the cruise control servo is affecting the throttle position.
• Vehicle speed inconsistent: Even without using cruise control, the vehicle speed might be inconsistent, fluctuating slightly due to the errant servo movement.

Possible Causes

• Faulty Cruise Control Servo: The servo motor itself may be malfunctioning internally. Over time, the motor, gears, or electronic components within the servo can wear out or fail, leading to inaccurate stroke positioning.
• Wiring Issues: Damaged, corroded, or shorted wiring in the cruise control system can disrupt the signals being sent to and from the servo. This includes the wiring harness connecting the servo to the PCM and other sensors.
• Vacuum Leaks: (If applicable) Some older cruise control systems rely on vacuum to operate the servo. Leaks in the vacuum lines can cause the servo to malfunction and register an incorrect stroke position. This is less common in newer, electronically controlled systems.
• Throttle Cable Issues: A binding or sticking throttle cable can prevent the servo from properly controlling the throttle. If the cable is not moving freely, the servo might overcompensate, resulting in a high stroke reading.
• Faulty Throttle Position Sensor (TPS): The TPS provides the PCM with information about the throttle position. If the TPS is providing inaccurate readings, the PCM might incorrectly interpret the servo position and trigger the P1569 code.
• Faulty Brake Switch: The brake switch signal is essential for disengaging the cruise control when the brake pedal is pressed. A faulty brake switch can prevent the cruise control from disengaging properly, leading to a high servo stroke reading even when the system is supposed to be off.
• Faulty Clutch Switch: (Manual Transmissions Only) Similar to the brake switch, the clutch switch disengages the cruise control when the clutch pedal is pressed. A malfunctioning clutch switch can have the same effect as a faulty brake switch.
• PCM (Powertrain Control Module) Issue: (Rare) While less common, a malfunctioning PCM can incorrectly interpret sensor data or send erroneous commands to the cruise control servo. This is usually a last resort diagnosis after all other possibilities have been ruled out.

Diagnostic Steps

1. Scan for other DTCs: Before focusing solely on the P1569 code, it's crucial to scan the vehicle's computer for any other Diagnostic Trouble Codes (DTCs). Other codes might provide clues about the underlying cause or indicate related issues that are affecting the cruise control system. Addressing these other codes first might resolve the P1569 code as well.
2. Inspect Wiring and Connectors: A thorough visual inspection of the wiring and connectors associated with the cruise control servo, TPS, brake switch, and clutch switch (if applicable) is essential. Look for any signs of damage, such as frayed wires, cracked insulation, or corroded connectors. Ensure that all connectors are properly seated and securely fastened.
3. Check Vacuum Lines (If Applicable): If the vehicle's cruise control system utilizes vacuum, carefully inspect all vacuum lines for leaks, cracks, or disconnections. Use a vacuum gauge to test the vacuum pressure within the system. Replace any damaged or leaking vacuum lines.
4. Test Cruise Control Servo: Use a multimeter and a scan tool (if available) to test the cruise control servo's functionality according to the manufacturer's specifications. Check the servo's resistance and voltage readings. A scan tool can be used to command the servo to move and verify that it responds correctly.
5. Test Throttle Position Sensor (TPS): Verify that the TPS signal is within the specified range using a multimeter. The TPS voltage should change smoothly and linearly as the throttle is opened and closed. Compare the TPS voltage readings to the manufacturer's specifications.
6. Test Brake Switch and Clutch Switch (If Applicable): Confirm that the brake switch and clutch switch (if applicable) are functioning correctly and sending the appropriate signals to the PCM. Use a multimeter to check the switch's continuity and voltage readings. The switches should change state when the brake or clutch pedal is pressed.
7. Check Throttle Cable: Ensure that the throttle cable moves freely and is not binding or sticking. Lubricate the cable if necessary. If the cable is damaged or frayed, it should be replaced.
8. Monitor Servo Position with Scan Tool: Use a scan tool to monitor the cruise control servo position while the vehicle is stationary and the cruise control is off. The reading should be within the specified range, typically close to zero. If the servo position is significantly higher than expected, it indicates a problem with the servo or its control circuit.
9. PCM Diagnosis: If all other components check out, consider the possibility of a PCM issue. This usually requires specialized diagnostic equipment and expertise to diagnose and repair. A PCM issue is relatively rare, so it should be considered as a last resort after all other potential causes have been eliminated.

Frequently Asked Questions

What does the P1569 code mean?

It means the cruise control servo is registering a high stroke position when the cruise control is not active. This indicates a malfunction in the cruise control system.

Can I still drive my car with a P1569 code?

While you can usually drive with this code, unintended acceleration is a potential risk. It is recommended to get it checked as soon as possible.

What is the most common cause of the P1569 code?

A faulty cruise control servo is often the culprit, but wiring issues are also common. Thoroughly inspect both before proceeding.

How do I fix the P1569 code?

Follow the diagnostic steps outlined above, starting with the simplest checks. Replacing the faulty component is usually the solution.

Will clearing the code fix the problem?

Clearing the code might temporarily remove the check engine light, but the underlying problem will persist and the code will likely return.

Conclusion

The P1569 code indicates a potentially serious issue with the cruise control system that requires prompt attention. By systematically diagnosing the possible causes and following the recommended repair steps, you can effectively resolve the problem and restore the proper functionality of the cruise control system, ensuring safe vehicle operation.