Skip to content
GTECH Calibration
Portal

P1587

Throttle Control Unit Modulated Command Malfunction.

  • Other
  • Powertrain
  • Manufacturer code
  • High severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
5
AreaVehicle speed, idle control and auxiliary inputs
87
FaultThe specific fault in that area

What it means

P1587 is a manufacturer-specific code. With the meaning given here, 'Throttle Control Unit Modulated Command Malfunction' (the Ford, Lincoln and Mercury definition), the throttle control unit or engine control unit has seen the modulated command signal to the electronic throttle drive disagree with what it expected, or fail a self-check. Other makes use P1587 for different faults, so confirm the definition against manufacturer data for the exact vehicle before diagnosing. The exact test that sets the code depends on the model and engine.

Symptoms

  • Engine warning light on and possibly a throttle or powertrain warning message
  • Reduced power or limp-home mode with restricted throttle opening
  • Hesitation, surging or unpredictable throttle response
  • Unstable or high idle, or stalling
  • Poor or delayed response to the accelerator pedal

Possible causes

  • Wiring or connector fault in the throttle motor drive or command circuits (chafing, corrosion, high resistance, loose pins)likely
  • Dirty, sticking or worn electronic throttle body or its motorlikely
  • Low system voltage, poor battery condition or poor earth or power supply to the throttle control unitpossible
  • Fault in the throttle position or accelerator pedal position sensor signals that the unit cross-checkspossible
  • Communication fault between the throttle control unit and the engine control unitpossible
  • Internal fault in the throttle control unit or engine control unitrare
  • Outdated control unit software where the manufacturer has issued a known fixrare

How to diagnose

  1. Read all stored and pending codes and the freeze frame data, noting any related throttle, pedal sensor, communication or voltage codes, then record before clearing anything
  2. Check the battery condition and charging voltage, and inspect the main power and earth connections
  3. Visually inspect the throttle body, its connector and the harness for damage, water ingress, corrosion or chafing
  4. Check the throttle body bore for heavy carbon build-up and whether the plate moves smoothly, with the ignition off
  5. With a scan tool, compare commanded and actual throttle angle and the accelerator pedal sensor values through the full range
  6. Test the throttle motor drive and sensor circuits for continuity, short circuits and voltage drop, following the manufacturer wiring diagram
  7. Check the power, earth and network communication at the throttle control unit and engine control unit
  8. Check for applicable service bulletins and software updates for the specific model and engine

How to fix

  • Repair or replace damaged wiring, terminals or connectors in the throttle control circuits
  • Clean the throttle body using the correct method, or replace it if worn or faulty, then carry out the throttle adaptation or relearn procedure
  • Restore proper battery and charging system performance and repair any power or earth faults
  • Replace a faulty accelerator pedal or throttle position sensor if tests confirm it
  • Repair network communication faults found on the data lines
  • Replace or reprogram the throttle control unit or engine control unit only once other causes are ruled out, and update software if an outdated version is a known cause

Can I keep driving?

High severity

Avoid driving if the car is in limp mode or the throttle responds unpredictably, as sudden loss of power or surging is unsafe in traffic. If it drives normally, keep trips short and cautious and get it diagnosed promptly.

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

This code for other makes

Nearby codes