P1567

What Does Code P1567 Mean?

DTC P1567 indicates a detected fault within the Speed Control Output Circuit Continuity by the Powertrain Control Module (PCM), often referred to as the Engine Control Module (ECM). This code is specific to the cruise control system, signifying that the PCM has identified an electrical integrity issue with the circuit responsible for controlling the speed control actuator or servo. The PCM continuously monitors the electrical characteristics of this output circuit, which could include current draw, voltage feedback, or resistance, to ensure that its commands to the speed control mechanism are being executed and that the circuit itself is intact. A “continuity” fault implies an open circuit (a break in the wire), an abnormally high resistance, or potentially a short to ground or voltage within the wiring or the actuator itself, preventing the PCM from reliably operating the speed control system. This subsystem is crucial for maintaining a driver-selected vehicle speed without manual throttle input.

Common Symptoms

• Inoperative Cruise Control System: The primary and most direct symptom will be the complete failure of the cruise control system to engage or maintain speed.
• Intermittent Cruise Control Function: The cruise control might work sometimes but fail at others, suggesting a marginal electrical connection or intermittent fault.
• Illumination of the Malfunction Indicator Lamp (MIL): The “Check Engine” or “Service Engine Soon” light will typically illuminate on the dashboard once the fault is confirmed by the PCM.
• Cruise Control Indicator Light Malfunction: The dedicated cruise control indicator light on the instrument cluster may not illuminate, flash erratically, or remain off when the system is commanded on.

What Causes the Code P1567?

• Open Circuit in Speed Control Output Wiring: A broken wire, corroded terminal, or loose connection within the harness leading to the speed control actuator can interrupt the circuit.
• Short Circuit to Ground or Voltage: The speed control output wire may be chafed or damaged, causing it to contact a chassis ground or another power source, leading to abnormal voltage or current readings.
• Faulty Speed Control Actuator/Servo: The internal electrical coil or motor within the speed control actuator (e.g., vacuum servo, electronic throttle body secondary motor) can develop an open, short, or excessively high resistance, disrupting the circuit continuity as monitored by the PCM.
• Damaged Clock Spring: On vehicles where speed control circuits route through the steering column’s clock spring assembly (for steering wheel-mounted controls), an internal fault in the clock spring can break the circuit.
• Blown Fuse: A fuse protecting the speed control system’s power supply or the actuator’s power circuit could be blown, resulting in an open circuit.
• Internal PCM/ECM Fault: While less common, a defective driver circuit within the PCM/ECM responsible for controlling the speed control output could fail, leading to misinterpretation or actual lack of continuity.

How to Diagnose and Troubleshoot

Diagnosing P1567 requires a methodical approach using a digital multimeter (DMM), an advanced OBD-II scan tool, and thorough visual inspection.

1. Retrieve and Document DTCs: Use an OBD-II scan tool to confirm P1567 is present. Check for any other related codes that might point to a common electrical fault or a specific component within the speed control system. Note freeze frame data.
2. Visual Inspection of Wiring and Connectors: Perform a detailed visual inspection of the entire speed control system wiring harness, from the PCM connector to the speed control actuator/servo. Look for signs of chafing, cuts, corrosion, bent pins, or loose connections. Pay close attention to areas where the harness passes through firewalls, along engine components, or near moving parts.
3. Check Fuses: Locate and inspect all fuses related to the speed control system and the powertrain control module. Replace any blown fuses, but be prepared to investigate the underlying cause of the blown fuse.
4. Speed Control Actuator Resistance Test:
   • Locate the speed control actuator/servo. Disconnect its electrical connector.
   • Using a DMM set to ohms, measure the resistance across the appropriate terminals of the actuator’s internal coil or motor.
   • Compare this reading to the manufacturer’s specified resistance values. An open circuit (infinite resistance) or a resistance value significantly outside specification indicates an internal fault within the actuator.
5. Continuity Test of Output Circuit Wiring:
   • With the ignition OFF and the PCM and actuator connectors disconnected, identify the specific output wire(s) from the PCM to the speed control actuator. Refer to a factory wiring diagram.
   • Using a DMM set to ohms, test for continuity between the PCM connector terminal and the corresponding actuator connector terminal. A reading of less than 5 ohms typically indicates good continuity. Infinite resistance or a very high reading indicates an open circuit.
   • While performing this test, gently flex and wiggle the harness to detect intermittent breaks.
6. Check for Short Circuits (to Ground and Voltage):
   • With the PCM and actuator connectors disconnected, set the DMM to ohms and measure resistance between the speed control output wire(s) at both the PCM and actuator connectors to a known good chassis ground. Infinite resistance is desired. Any low resistance indicates a short to ground.
   • Reconnect the PCM and actuator connectors. Turn the ignition to the ON position (engine OFF). Using the DMM set to DC volts, back-probe the speed control output wire(s) at the actuator connector. Check for any unintended voltage present, which would indicate a short to voltage.
7. Clock Spring Inspection (if applicable): If the speed control circuit passes through the clock spring, perform continuity tests through the clock spring with the steering wheel rotated to various positions. An open circuit at certain rotations indicates a faulty clock spring.

Recommended Repairs and Solutions

Once the root cause of P1567 has been precisely identified through diagnosis, the following repairs are typically recommended:

• Repair or Replace Damaged Wiring: If an open circuit, short to ground, or short to voltage is found in the wiring harness, the damaged section should be professionally repaired using soldering and heat-shrink tubing, or the entire sub-harness replaced if damage is extensive. Always ensure proper wire gauge and insulation.
• Replace Corroded or Damaged Connectors: If corrosion or damage is found on connector terminals, attempt to clean them thoroughly with electrical contact cleaner. If pins are bent, broken, or excessively corroded, the connector body and terminals should be replaced.
• Replace the Speed Control Actuator/Servo: If the actuator itself fails the resistance test or shows signs of internal electrical failure, it must be replaced. Ensure the new component is an OEM or high-quality aftermarket equivalent.
• Replace the Clock Spring: If diagnostic steps confirm an internal failure of the clock spring assembly is interrupting the speed control circuit, it must be replaced. Follow manufacturer guidelines for clock spring replacement, which often involves steering wheel and airbag removal.
• Replace Blown Fuses: If a blown fuse was discovered, replace it with a fuse of the correct amperage. However, it is critical to determine and rectify the underlying cause of the blown fuse to prevent immediate recurrence.
• PCM/ECM Replacement/Reprogramming: Only consider PCM/ECM replacement as a last resort, after all other components and wiring have been thoroughly tested and verified as functional. PCM replacement typically requires specialized programming and calibration for the specific vehicle.

Mechanics’ Tip: Always clear the DTCs after performing repairs and conduct a thorough road test to ensure the cruise control system functions correctly and the code does not return. Pay attention to intermittent functionality during the test drive.