Corroded, loose, or damaged wiring and connectors at the throttle actuator control module or throttle body; Failing throttle actuator control module or electronic throttle body assembly; Low or unstable battery voltage causing modules to broadcast corrupt data; CAN bus communication faults such as chafed wiring, poor grounds, or failed terminating resistors; Software or calibration issues in the throttle actuator control module requiring reflash; Water intrusion into the throttle body connector or module housing; Aftermarket electronic throttle controllers or piggyback devices interfering with network data

DTC codes / U04xx · Invalid data received from a module / U0408

U0408Invalid Data Received From Throttle Actuator Control Module

Q: What does code U0408 mean?

Invalid Data Received From Throttle Actuator Control Module. U0408 is a communication fault where one or more control modules receive data from the throttle actuator control module that the network considers invalid or implausible. The throttle actuator control module is responsible for operating the electronic throttle body, and when its broadcast data fails plausibility checks, the receiving modules set this code and typically illuminate the warning light.

U0408 is a communication fault where one or more control modules receive data from the throttle actuator control module that the network considers invalid or implausible. The throttle actuator control module is responsible for operating the electronic throttle body, and when its broadcast data fails plausibility checks, the receiving modules set this code and typically illuminate the warning light.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaInvalid data received from a module

Symptoms you may notice

Illumination of the check engine light or electronic throttle control warning light
Reduced engine power or limp-home mode with limited throttle response
Rough or erratic idle quality
Hesitation or stumble during acceleration
Often no symptoms besides the warning light if the fault is intermittent
Multiple unrelated warning lights if the throttle actuator control module shares a network segment with other modules

Common causes, most likely first

Corroded, loose, or damaged wiring and connectors at the throttle actuator control module or throttle body
Failing throttle actuator control module or electronic throttle body assembly
Low or unstable battery voltage causing modules to broadcast corrupt data
CAN bus communication faults such as chafed wiring, poor grounds, or failed terminating resistors
Software or calibration issues in the throttle actuator control module requiring reflash
Water intrusion into the throttle body connector or module housing
Aftermarket electronic throttle controllers or piggyback devices interfering with network data

How to diagnose and fix it

Perform a full scan of all modules and record every stored, pending, and permanent code before clearing anything
Inspect the throttle body and throttle actuator control module connectors for corrosion, water intrusion, and loose pins
Check battery voltage and charging system output, as low voltage commonly corrupts module data
Measure CAN bus resistance and verify communication integrity between the throttle actuator control module and other modules
Check grounds and power feeds to the throttle actuator control module for voltage drop
If wiring and power are good, substitute a known-good throttle body or module and recheck for the code
After repair, clear codes and perform a throttle relearn or idle relearn procedure as required by the manufacturer

Why U0408 is often a wiring fault

This code frequently sets because of a poor connection at the throttle body connector rather than a failed throttle actuator control module, so inspect terminals before condemning parts.
Low battery voltage or a weak charging system can cause the throttle actuator control module to broadcast invalid data, setting U0408 without any hard fault in the module itself.
Aftermarket throttle controllers and piggyback tuners that tap into the pedal or throttle wiring are a common cause of invalid data codes on the network.
U0408 does not always mean the throttle actuator control module is faulty; it can be set by a receiving module that misinterprets valid data due to its own communication fault.
A throttle body that is mechanically sticking or carbon-fouled can cause the actuator control module to report implausible position data, triggering this code even when the electronics are healthy.

Can I keep driving with U0408?

If the vehicle is in limp-home mode or the throttle response is erratic, avoid driving and have it towed because reduced power can be unsafe in traffic. If the light is on but the car drives normally, you can drive cautiously to a repair shop, but avoid hard acceleration and long trips until the fault is diagnosed.

Tools that help

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