What Does P1604 Mean?
This code indicates the Throttle Control Unit (TCU) or PCM is unable to achieve the desired throttle angle. Unlike P1586 which indicates a position mismatch, this code specifically flags the system's inability to reach the commanded position, often due to a mechanical limitation or motor performance degradation. The vehicle will enter reduced power mode to protect the drivetrain.
Safety Warning
Reduced power mode limits vehicle speed and acceleration, which can be dangerous in situations requiring full power such as merging onto highways. A throttle that cannot reach desired positions may also cause poor drivability.
Common Causes
30%
Electronic throttle body motor degradation or failure
25%
Heavy carbon deposits restricting throttle blade travel
20%
Low voltage to the throttle motor due to power supply issues
15%
Foreign object or debris lodged in the throttle bore
10%
Throttle body mechanical wear causing excessive friction
Diagnostic Steps
1
Command the throttle to various positions using scan tool bi-directional control and note where it fails to reach the target—this identifies partial vs. complete failure.
2
Check the voltage supply to the throttle body motor pins with the engine running; verify battery voltage is present.
3
Remove the intake ducting and visually inspect the throttle blade and bore for carbon, debris, or mechanical damage.
4
If carbon buildup is present, clean the throttle body with approved cleaner and retest the actuator travel range.
5
Measure throttle motor current draw during actuation; excessive draw indicates mechanical binding, while no draw indicates an electrical open.
6
Replace the throttle body if the motor is weak or the mechanism is worn, then perform the relearn procedure.
Estimated Repair Cost
$200 - $650
Parts + labor, varies by vehicle and location
This code indicates the Throttle Control Unit (TCU) or PCM is unable to achieve the desired throttle angle. Unlike P1586 which indicates a position mismatch, this code specifically flags the system's inability to reach the commanded position, often due to a mechanical limitation or motor performance...
The most common cause of P1604 (TCU Unable To Control Desired Throttle Angle) is: Electronic throttle body motor degradation or failure
Typical repair costs for P1604 range from $200 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Reduced power mode limits vehicle speed and acceleration, which can be dangerous in situations requiring full power such as merging onto highways. A throttle that cannot reach desired positions may also cause poor drivability.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1604 to identify the root cause.
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Quick Info
Category
Powertrain
System
Electronic Throttle Control
Difficulty
Type
Manufacturer
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