Faulty or misadjusted brake pedal switch or cruise release switch giving an incorrect signal; Wiring damage, corrosion or poor connections in the cruise control, throttle or brake switch circuits; Throttle body or throttle position sensor fault, or dirty throttle body affecting power management; Faulty cruise control switch on the steering wheel or column; Vehicle speed signal problem, such as a wheel speed sensor or related module fault; Low battery voltage or charging system fault upsetting the control module; Internal powertrain control module fault or outdated software, where a known issue is documented for the model.

P1559

Cruise Control Power Mangement Mode.

Buick
Powertrain
Manufacturer code
Low severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
5: AreaVehicle speed, idle control and auxiliary inputs
59: FaultThe specific fault in that area

What it means

On a Buick, P1559 relates to the Cruise Control Power Management Mode. The powertrain control module has detected a fault in how cruise control and engine power management are working together, so cruise control may be restricted or disabled. The exact set conditions depend on the model, engine and year, so check the manufacturer's information for the vehicle in question.

Symptoms

Cruise control will not engage or drops out unexpectedly
Cruise control indicator or malfunction message displayed
Engine management warning light on
Reduced or inconsistent throttle response
Other stored codes relating to throttle, brake switch or vehicle speed

Possible causes

Faulty or misadjusted brake pedal switch or cruise release switch giving an incorrect signallikely
Wiring damage, corrosion or poor connections in the cruise control, throttle or brake switch circuitslikely
Throttle body or throttle position sensor fault, or dirty throttle body affecting power managementpossible
Faulty cruise control switch on the steering wheel or columnpossible
Vehicle speed signal problem, such as a wheel speed sensor or related module faultpossible
Low battery voltage or charging system fault upsetting the control modulepossible
Internal powertrain control module fault or outdated software, where a known issue is documented for the modelrare

How to diagnose

Read all stored codes and freeze frame data, and note any related throttle, brake, speed or voltage codes
Check battery condition and charging voltage, as low voltage can cause spurious faults
Inspect the brake pedal switch for correct operation, adjustment and brake light function
Visually inspect wiring and connectors to the cruise control switches, throttle body and powertrain control module for damage, corrosion or looseness
Check the cruise control switch operation and view its live data inputs on a scan tool
Compare live throttle position and vehicle speed data against expected values for smooth, plausible readings
Inspect and, if appropriate for the model, clean the throttle body and check throttle operation
Check for manufacturer service bulletins or software updates relevant to the vehicle

How to fix

Replace or readjust the brake pedal or cruise release switch if faulty
Repair damaged wiring or connectors and clean corroded terminals
Replace a faulty cruise control switch or clock spring if the switch signal is erratic
Clean or replace the throttle body if its operation is faulty, and carry out any relearn the model requires
Correct charging or battery faults
Update or replace the powertrain control module only if a known fault or outdated calibration is confirmed

Can I keep driving?

Low severity

The car can normally be driven as usual without cruise control, so book it in for diagnosis. If throttle response is poor or other warnings appear, have it checked sooner.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.