Dirty or carbon-fouled throttle body causing the plate to stick or respond slowly; Faulty throttle body or throttle actuator motor; Faulty throttle position sensor signals or accelerator pedal position sensor signals that disagree with each other; Wiring damage, corrosion or poor connections in the throttle or pedal circuits; Low or unstable supply voltage or poor earths, from a weak battery or charging fault; Unplanned air leak after the throttle body upsetting the throttle model; Fault in the engine control module itself or an outdated calibration, where a known bulletin applies to the model.

P1511

Throttle Control System Backup System Performance.

Buick
Powertrain
Manufacturer code
High severity

How this code is built

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

What it means

P1511 on a Buick means the engine control module has found a performance problem with the backup system for the electronic throttle control. The module monitors the throttle position, accelerator pedal position and the throttle motor's response, and compares them with what it commanded. When the backup or redundant strategy cannot confirm the throttle is behaving as expected, it sets the code and may limit engine power.

Symptoms

Reduced engine power or limp-home mode
Throttle Control or reduced power warning on the dashboard
Check engine light on
Poor or delayed throttle response
Rough, high or unstable idle
Engine stalling or hesitation at low speed

Possible causes

Dirty or carbon-fouled throttle body causing the plate to stick or respond slowlylikely
Faulty throttle body or throttle actuator motorlikely
Faulty throttle position sensor signals or accelerator pedal position sensor signals that disagree with each otherlikely
Wiring damage, corrosion or poor connections in the throttle or pedal circuitspossible
Low or unstable supply voltage or poor earths, from a weak battery or charging faultpossible
Unplanned air leak after the throttle body upsetting the throttle modelpossible
Fault in the engine control module itself or an outdated calibration, where a known bulletin applies to the modelrare

How to diagnose

Read all stored and pending codes and freeze frame data, noting speed, load and battery voltage when the code set, and look for other throttle or pedal codes
Check battery condition and charging voltage, as low voltage can upset throttle control monitoring
Inspect the throttle body connector, wiring and earths for damage, corrosion, chafing or water ingress
Inspect the throttle body bore and plate for carbon build-up and check the plate moves freely by hand with the ignition off
With a scan tool, compare commanded and actual throttle angle and the accelerator pedal sensor readings while moving the pedal slowly through its range
Check that the sensor readings track smoothly and agree with each other without dropouts or jumps
Check for vacuum or intake leaks after the throttle body and for any recent work that disturbed the intake
Check the wiring resistance and supply and reference voltages at the throttle body and pedal connectors against the model's service data

How to fix

Clean the throttle body using a method suitable for the model, then perform the throttle relearn procedure
Replace the throttle body assembly if the motor or position sensors are faulty or the plate sticks
Replace the accelerator pedal assembly if its sensor signals are erratic or disagree
Repair damaged wiring, connectors or earths in the throttle and pedal circuits
Correct battery or charging faults to restore stable supply voltage
Repair any intake leak, and update the control module calibration only if a known fault for that model calls for it

Can I keep driving?

High severity

Avoid driving the car if it is in limp-home mode or the throttle response is unpredictable, as power may drop suddenly in traffic. If it is running normally, drive only a short distance carefully to get it repaired.

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