P1561
Cruise Vent Solenoid.
- GMC
- Powertrain
- Manufacturer code
- Low severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 61
- FaultThe specific fault in that area
What it means
P1561 on a GMC is a manufacturer-specific code relating to the cruise vent solenoid circuit. The cruise vent solenoid releases vacuum from the cruise control servo so the throttle returns and cruise cancels. The control unit sets the code when it sees an electrical fault or a response that does not match the commanded state of the solenoid. The exact circuit and strategy depend on the model, engine and year.
Symptoms
- Cruise control will not engage or drops out unexpectedly
- Cruise control will not cancel promptly when the brake is pressed
- Cruise control indicator light flashing or the system disabled
- Malfunction indicator lamp on, depending on the model
- Cruise speed hunting or surging on a vacuum-operated system
Possible causes
- Faulty cruise vent solenoid (open or shorted coil)likely
- Damaged wiring, chafing or corrosion in the solenoid circuitlikely
- Poor connection at the solenoid or control unit connectorpossible
- Leaking, split or blocked vacuum hose to the servo or solenoidpossible
- Faulty cruise servo or release valve assemblypossible
- Fault in the control unit driver circuitrare
How to diagnose
- Read all stored codes and freeze frame data, and note whether other cruise, brake switch or throttle codes are present
- Check cruise control operation and whether the brake switch cancels it
- Visually inspect the solenoid, its connector and the wiring for chafing, heat damage, corrosion or water ingress
- Inspect the vacuum hoses and servo for splits, kinks, blockages or loose fittings
- Measure the solenoid coil resistance and compare it with the specification for the model
- Check the supply voltage and ground at the solenoid connector with the ignition on
- Command the solenoid with a suitable scan tool test, if supported, and confirm it clicks and changes vacuum
- Check for open circuit, short to ground or short to voltage in the control wire back to the control unit
How to fix
- Replace the cruise vent solenoid if the coil or operation is faulty
- Repair or replace damaged wiring and clean or renew corroded connector terminals
- Renew split, perished or blocked vacuum hoses and fittings
- Replace the cruise servo or release valve assembly if it fails testing
- Check for a software update for the control unit only if a known calibration issue applies to the model, and clear the code after repair
Can I keep driving?
Low severity
The car can normally be driven, but cruise control may not work or cancel properly, so avoid relying on it. Book the repair in soon, especially if cruise fails to cancel when the brake is pressed.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.