U0408
Invalid Data Received From Throttle Actuator A Control Module
Communication network (throttle control)
Generic OBD-II
High
What it means
U0408 sets when a control module reads data from the throttle actuator (throttle-by-wire) control module that is missing, out of range, or implausible. Since this module controls how far the throttle opens, bad data usually pushes the engine into a reduced-power or fixed-idle failsafe, and in some cases can cause stalling.
High
Can I keep driving? Risky — the engine may drop to reduced-power or a fixed-idle failsafe for safety, so get it checked before driving far.
Common symptoms
What you'll notice
- Check-engine light on, usually with a reduced-power warning
- Poor or unresponsive throttle, or the engine won't rev normally
- Engine drops into limp mode or a fixed fast idle
- Possible stall or hard-to-drive behavior
- Related communication codes stored in other modules
Common causes
Most likely first
- Faulty throttle actuator control module or its power/ground supplyLikely
- Corroded, loose, or damaged connectors and data-bus (CAN) wiringCommon
- Low or unstable battery and charging-system voltageCommon
- Software incompatibility after a module was replaced or updatedLess often
- An underlying throttle-body or pedal-sensor fault reported by the moduleLess often
How to diagnose & fix
Work through it in order
- Scan every module and record all stored codes and freeze-frame data before clearing.
- Check battery and charging voltage — weak or noisy voltage often triggers bus data errors.
- Inspect the connectors and wiring to the throttle actuator control module and along the data bus.
- If a module was recently replaced or flashed, confirm the software is correct and compatible.
- Follow the manufacturer's pinpoint tests for the throttle module; replace it only after power, grounds, and wiring check out.
FAQ
Quick answers
Is it safe to drive with U0408?+
Not really — throttle-control faults can force the engine into reduced power or a failsafe idle, which is unsafe in traffic. Get it diagnosed before driving far.
Can I just clear U0408?+
You can, but if the throttle module or its data link is still faulty the code returns quickly, often with the engine going straight back into limp mode.
Related codes
Often seen with U0408
Read & clear U0408 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX