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DTC codes / GM codes / P1562

P1562 · GMCruise Vacuum Solenoid

P1562 on a GM vehicle indicates that the powertrain control module (PCM) has detected an electrical fault in the cruise control vacuum solenoid circuit, which controls the vacuum supply to the cruise control servo. The PCM monitors the solenoid's command and feedback circuits and sets this code when the voltage or current falls outside the expected range, preventing the cruise control system from engaging or holding speed.

SystemPowertrain
Code typeGM specific
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • The cruise control will not engage or will disengage unexpectedly while driving.
  • The cruise control indicator light may flash or remain off when you try to set a speed.
  • Often no symptoms besides the warning light, especially if the solenoid fails in a state that does not affect other systems.
  • A slight hesitation or surge may be felt if the solenoid is stuck open and causes a small vacuum leak.
  • On some models, the engine may idle slightly rough or have a minor vacuum leak that affects fuel trims.
  • The brake pedal may feel normal, but the cruise control will not resume after braking.

Common causes, most likely first

  1. Failed cruise control vacuum solenoid, often due to a burned-out coil or stuck plunger.
  2. Damaged or disconnected wiring harness at the solenoid connector, including chafed wires or corroded pins.
  3. Blown fuse or faulty relay that supplies power to the cruise control vacuum solenoid circuit.
  4. Vacuum leaks in the hose between the solenoid and the cruise servo, or a cracked solenoid housing.
  5. Corrosion or water intrusion in the solenoid connector, common on older GM vehicles in wet climates.
  6. A faulty PCM driver circuit, though this is rare and should only be suspected after all other causes are ruled out.

How to diagnose and fix it

  1. Inspect the cruise control vacuum solenoid connector and wiring for corrosion, chafing, or loose pins, and repair as needed.
  2. Check the fuse and relay that supply power to the solenoid circuit, and replace any blown fuse or faulty relay.
  3. Test the solenoid's resistance with a multimeter and compare to the manufacturer's specification; replace the solenoid if out of range.
  4. Apply vacuum to the solenoid and verify it holds and releases when powered, replacing it if it does not operate correctly.
  5. Inspect all vacuum hoses connected to the solenoid and servo for cracks or disconnections, and replace any damaged hose.
  6. Clear the code and test-drive the vehicle to confirm the cruise control engages and the code does not return.
  7. If the code persists after all electrical and vacuum checks, perform a pinpoint test of the PCM driver circuit using a scan tool and wiring diagram.

Cruise Vacuum Solenoid Diagnosis Traps

  • A stuck-open solenoid can cause a small vacuum leak that affects engine idle and fuel trims, leading technicians to chase engine performance issues instead of the cruise control system.
  • The solenoid often fails intermittently, so the code may set only after prolonged driving or in certain temperature conditions, making it easy to misdiagnose as a wiring issue.
  • On many GM vehicles, the cruise control vacuum solenoid shares a ground with other components, so a bad ground can set P1562 along with other codes, and cleaning the ground point may fix it.
  • Replacing the solenoid without checking the vacuum hoses is a common mistake; a collapsed or leaking hose can cause the new solenoid to fail or the code to return.
  • Some aftermarket solenoids have different resistance values than the OEM part, which can trigger P1562 even when the new part is functioning, so always verify resistance before installation.

Can I keep driving with P1562?

You can drive the vehicle safely with P1562 because the cruise control system is disabled and normal braking and throttle operation are unaffected. Avoid using the cruise control until the fault is repaired, and be aware that a small vacuum leak from a failed solenoid could slightly affect engine idle quality.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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