Damaged or chafed wiring in the throttle control unit modulated command circuit; Corroded or loose electrical connector at the throttle body or PCM; Faulty throttle body assembly with an internal electronic fault in the command circuit; PCM software calibration issue or internal driver fault; Poor ground connection for the throttle control unit or PCM; Aftermarket electronic throttle controller or piggyback device interfering with the command signal

DTC codes / Ford codes / P1587

P1587 · FordThrottle Control Unit Modulated Command Malfunction

Q: What does code P1587 mean?

Throttle Control Unit Modulated Command Malfunction. P1587 on Ford vehicles indicates that the powertrain control module (PCM) has detected a malfunction in the modulated command signal it sends to the throttle control unit, which is part of the electronic throttle control system. The PCM expects a specific pulse-width-modulated (PWM) signal to control the throttle plate, but the feedback or circuit response falls outside the expected range, so the computer sets this code and typically illuminates the wrench light.

P1587 on Ford vehicles indicates that the powertrain control module (PCM) has detected a malfunction in the modulated command signal it sends to the throttle control unit, which is part of the electronic throttle control system. The PCM expects a specific pulse-width-modulated (PWM) signal to control the throttle plate, but the feedback or circuit response falls outside the expected range, so the computer sets this code and typically illuminates the wrench light.

SystemPowertrain

Code typeFord specific

SeverityMedium

Fix difficultyIntermediate

AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

Illumination of the powertrain malfunction or wrench indicator light on the dashboard
Reduced engine power or limp-home mode with limited throttle response
Hesitation or stumble when accelerating from a stop
Unstable or surging idle quality
Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

Damaged or chafed wiring in the throttle control unit modulated command circuit
Corroded or loose electrical connector at the throttle body or PCM
Faulty throttle body assembly with an internal electronic fault in the command circuit
PCM software calibration issue or internal driver fault
Poor ground connection for the throttle control unit or PCM
Aftermarket electronic throttle controller or piggyback device interfering with the command signal

How to diagnose and fix it

Connect a scan tool and record all stored codes, freeze-frame data, and throttle position sensor readings to confirm P1587 is the primary fault.
Visually inspect the throttle body connector and PCM connector for corrosion, pushed pins, or loose terminals, and repair as needed.
Perform a wiggle test on the throttle control unit command wire while monitoring the commanded and actual throttle position on the scan tool to reveal intermittent wiring faults.
Check the throttle control unit command circuit for continuity, short to ground, and short to power using a digital multimeter, and repair any damaged wiring.
Verify the throttle body is clean and the plate moves freely without binding, and clean the throttle bore if carbon buildup is present.
If wiring and connectors are good, substitute a known-good throttle body and clear the code to see if the fault returns.
As a last step, check for Ford technical service bulletins (TSBs) or PCM calibration updates that address P1587, and reprogram or replace the PCM only if all other causes are ruled out.

Don't replace the throttle body first

A loose or corroded throttle body connector is a far more common cause of P1587 than a failed throttle body, so always inspect and clean the terminals before condemning the assembly.
Intermittent P1587 codes often appear after engine work that disturbs the throttle body harness, so check for stretched or pinched wires near the intake manifold.
Aftermarket throttle controllers or performance tuners that splice into the pedal or throttle wiring can corrupt the modulated command signal and set this code, so remove them before diagnosing.
A weak battery or poor ground can cause the PCM to misread the throttle command signal, so verify battery voltage and ground integrity before replacing expensive parts.
P1587 can be stored alongside throttle actuator control codes, but it specifically points to the command signal path rather than the motor circuit, so do not confuse it with P2100-series codes.

Can I keep driving with P1587?

You can usually drive the vehicle to a repair shop, but expect reduced power and avoid heavy acceleration or highway merging until the fault is repaired. If the vehicle enters limp mode or the throttle response becomes unpredictable, stop driving and have it towed.

Tools that help

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Guidance is general and written for Ford vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.