What Does P1587 Mean?
This code indicates the throttle control unit has detected a malfunction in its modulated (PWM) command signal to the throttle motor. The PCM sends a pulse-width-modulated signal to precisely control throttle blade position, and a fault in this control path means the system cannot accurately regulate airflow. The vehicle will typically enter reduced power mode.
Safety Warning
Loss of precise throttle control is a significant safety concern. The vehicle will operate in reduced power mode, but intermittent faults could cause unexpected throttle behavior during driving.
Common Causes
30%
Faulty electronic throttle body motor (armature or brush wear)
25%
PCM throttle driver circuit malfunction
20%
Damaged or corroded wiring between PCM and throttle body motor
15%
Poor ground connection at the throttle body or PCM
10%
Electromagnetic interference from aftermarket electronics
Diagnostic Steps
1
Monitor the throttle motor command duty cycle and actual throttle position on live data; look for erratic or stuck command values.
2
Inspect the throttle body connector pins for signs of overheating, corrosion, or pin spread.
3
Check the throttle motor control circuit wiring from PCM to throttle body for opens, shorts, or high resistance using a DVOM.
4
Verify PCM power and ground circuits are within specification, as low voltage can affect PWM output accuracy.
5
If wiring checks pass, swap or replace the throttle body assembly and perform the relearn procedure.
6
Clear codes and road test under varying conditions including cold start, idle, and wide-open throttle.
Estimated Repair Cost
$250 - $750
Parts + labor, varies by vehicle and location
This code indicates the throttle control unit has detected a malfunction in its modulated (PWM) command signal to the throttle motor. The PCM sends a pulse-width-modulated signal to precisely control throttle blade position, and a fault in this control path means the system cannot accurately regulat...
The most common cause of P1587 (Throttle Control Unit Modulated Command Malfunction) is: Faulty electronic throttle body motor (armature or brush wear)
Typical repair costs for P1587 range from $250 to $750, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of precise throttle control is a significant safety concern. The vehicle will operate in reduced power mode, but intermittent faults could cause unexpected throttle behavior during driving.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1587 to identify the root cause.
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Quick Info
Category
Powertrain
System
Electronic Throttle Control
Difficulty
Type
Manufacturer
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