U0408

Invalid Data Received From Throttle Actuator Control Module

U0408 is a generic OBD-II network diagnostic trouble code: Invalid Data Received From Throttle Actuator Control Module. It is logged by the engine control unit when the throttle monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
U0408
Group
Network
System
Throttle
Severity
Warning (MIL on, possible limp mode)
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What U0408 means

U0408 is set when a receiving module, typically the ECM or PCM, detects that the Throttle Actuator Control Module (TACM) is present on the network and actively transmitting, but its message content fails plausibility, range, checksum, or counter validation. Unlike a lost-communication code, the module is communicating, but the data it reports is not trustworthy.

The throttle actuator control module manages the electronic throttle body, commanding the throttle plate position and reporting throttle position feedback, motor current, and fault status to the engine controller. Because electronic throttle control is safety-relevant, the ECM continuously cross-checks this data against accelerator pedal and other inputs. When the reported throttle data is implausible, the ECM commonly enters a reduced-power or limp mode and limits throttle authority to protect the driver and drivetrain.

Invalid data can result from a failing throttle actuator module, a wiring or connector fault that corrupts signals on the bus, electrical noise, or an unstable power or ground supply to the module. A software mismatch after replacement can also cause messages that fail the ECM sanity checks. Diagnosis should read all DTCs, monitor throttle live data, and inspect the harness and supply before condemning the module.

Common causes

Most-frequently reported root causes when U0408 is logged.

  • 1
    Failing throttle actuator control module transmitting out-of-range or corrupted data.
  • 2
    Damaged wiring or corroded connector on the throttle actuator module circuit.
  • 3
    Incorrect software version or improper programming after module replacement.
  • 4
    Faulty throttle position feedback sensor producing implausible values.
  • 5
    Unstable power or poor ground to the throttle actuator module causing erratic frames.
  • 6
    Electrical noise or interference corrupting CAN messages on the module segment.
  • 7
    CAN bus wiring fault or failing termination resistor affecting message integrity.

Symptoms drivers notice

Reduced engine power or limp mode with limited throttle response.
MIL illuminated, often with a throttle or powertrain warning lamp.
Hesitation, surging, or poor acceleration.
Erratic or stuck idle speed.
Additional electronic throttle or network DTCs may be stored.

How to diagnose U0408

A typical diagnostic flow when this code is present.

  1. 1
    Read all DTCs from the ECM and related modules before clearing anything.
  2. 2
    Monitor throttle actuator live data for out-of-range or erratic throttle position values.
  3. 3
    Inspect the throttle actuator module harness and connector for damage or corrosion.
  4. 4
    Check power and ground supply circuits to the module for proper voltage and low resistance.
  5. 5
    Verify CAN bus integrity and termination on the segment shared with the module.
  6. 6
    Confirm the module software version matches the vehicle configuration.
  7. 7
    Replace or reprogram the throttle actuator module only after wiring and supply checks pass.

Related network codes

Frequently asked questions

Is U0408 the same as a lost-communication code?

No. U0408 means the throttle actuator control module is communicating but sending invalid or implausible data, whereas a lost-communication code means no messages are received at all.

Why does U0408 often trigger limp mode?

Electronic throttle control is safety-critical, so when throttle data is untrustworthy the ECM limits throttle authority and power to keep the vehicle controllable.

Can wiring problems alone cause U0408?

Yes. Corroded connectors, chafed wiring, or a poor ground can corrupt the module's data and set the code without the module itself being faulty.

Does the throttle actuator module need programming after replacement?

On many vehicles the replacement module must be configured or reflashed to match the vehicle to avoid data and calibration mismatches.

Disabling U0408 in software

RaceTune can permanently disable U0408 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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