Wiring or connector fault in the throttle control circuit (chafing, corrosion, loose pins); Dirty or faulty throttle body or sticking throttle plate; Faulty throttle position sensor or accelerator pedal position sensor giving implausible signals; Low supply voltage or poor earth affecting the throttle motor or sensors; Faulty throttle actuator or throttle motor drive; Engine control unit fault or outdated calibration (only where the manufacturer lists it as a known cause).

P1220

Series Throttle Control Fault.

Mercury
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
2: AreaFuel and air metering (injector circuit)
20: FaultThe specific fault in that area

What it means

On Mercury (Ford group) vehicles, P1220 means Series Throttle Control Fault. The engine control unit has detected a problem in the series throttle control arrangement, where the throttle is regulated through a secondary or series control path in addition to the driver's pedal demand. The code is set when the commanded and actual throttle behaviour, or the related control signals, do not agree. Exact operation depends on the model and engine, so confirm against the manufacturer's data for the specific vehicle.

Symptoms

Engine warning light on
Reduced power or limp-home mode
Poor or delayed throttle response
Unstable or high idle
Hesitation or surging when accelerating
Possible hard starting

Possible causes

Wiring or connector fault in the throttle control circuit (chafing, corrosion, loose pins)likely
Dirty or faulty throttle body or sticking throttle platelikely
Faulty throttle position sensor or accelerator pedal position sensor giving implausible signalspossible
Low supply voltage or poor earth affecting the throttle motor or sensorspossible
Faulty throttle actuator or throttle motor drivepossible
Engine control unit fault or outdated calibration (only where the manufacturer lists it as a known cause)rare

How to diagnose

Read all stored and pending codes and record the freeze frame data, noting any other throttle, pedal or voltage codes.
Visually inspect the throttle body, pedal assembly and related wiring and connectors for damage, corrosion, oil or water ingress.
Check battery condition and charging voltage, and inspect the engine and body earths.
Inspect the throttle body bore and plate for carbon build-up and check that it moves freely by hand with the ignition off.
With a scan tool, compare commanded and actual throttle angle and both pedal and throttle sensor readings through the full range, looking for dropouts or disagreement.
Test the throttle circuit supply, reference, signal and earth wires for continuity, shorts and resistance against the manufacturer's wiring data.
Check the throttle motor drive signal and resistance to the manufacturer's specification, as procedures vary by model and engine.
Check for applicable technical bulletins or calibration updates for the vehicle before replacing the control unit.

How to fix

Repair or replace damaged wiring, terminals or connectors in the throttle control circuit.
Clean the throttle body using the manufacturer's recommended method, then carry out any throttle relearn or adaptation procedure.
Replace a faulty throttle position sensor, pedal sensor or throttle body assembly as diagnosed.
Restore battery, charging or earth faults that cause low or unstable voltage.
Update or correct the engine control unit calibration only if a known fault applies, or repair or replace the control unit if proven faulty.

Can I keep driving?

Medium severity

The car may run in a reduced-power mode, and throttle response can be unpredictable, so avoid long journeys and busy overtaking. Have it diagnosed soon, and stop driving if power loss becomes severe or the throttle behaves erratically.

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