U0408

Code

HYUNDAI U — Network/User

Invalid Data Received From Throttle Actuator Control Module

Brand: HYUNDAI

Type: U — Network/User

Views: UK: 11 EN: 22 RU: 21

AI status

Completed

ready

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Page language: EN

Causes

Faulty or unresponsive Throttle Actuator Control (TAC) module
CAN bus communication fault (open/short/low termination, nodes not present)
Corroded, loose, or damaged connectors or wiring to TAC module
Poor power supply or ground to TAC module (low battery voltage, bad ground)
Software mismatch, incorrect module programming, or failed reflash
Faulty ECM or another module sending bad messages

Symptoms

Malfunction Indicator Lamp (MIL) or warning light illuminated
Reduced engine power / limp-home mode
Poor or no throttle response, delayed throttle
Erratic idle or surging
Other network-related warnings or inoperative systems that share CAN

What to check

Read freeze frame and full DTC list and note active vs stored faults
Scan the network; confirm TAC module is present and responsive in the scan tool
Check for additional U-codes (other module communication faults)
Measure battery voltage with key on/engine off; verify stable supply
Visually inspect TAC module connector and wiring for corrosion, damage, or water ingress
Check CAN bus wiring continuity and resistance between nodes; verify bus termination resistors ~60 ohms (two 120Ω in parallel)

Signal parameters

CAN bus idle (recessive): CANH ~2.5 V, CANL ~2.5 V (both near mid-rail)
CAN dominant state: CANH typically rises toward ~3.5 V and CANL falls toward ~1.5 V (differential ~2 V)
Expected CAN message rate for throttle/status messages: periodic updates (tool-dependent) — messages should be consistent, not sporadic or missing
TAC module supply: battery voltage (~11–14.5 V) with key on/run
Ground: near 0 V with low resistance to chassis
Throttle sensor outputs: within expected 0.5–4.5 V ranges and show smooth, correlated changes when pedal or throttle commanded

Diagnostic algorithm

Verify the code: connect a capable scan tool, confirm U0408 is present and note whether it is active or stored. Clear codes and attempt to reproduce.
Check for related codes: record other U or P codes; multiple module communication errors often indicate bus-level issues.
Confirm module presence: use the scan tool to query the TAC module for identity, status, and live data. If the module does not respond, suspect wiring/termination/power or module failure.
Inspect connectors and wiring: visually and physically inspect TAC harness, pins, and connectors for corrosion, bent pins, water intrusion, or damage. Repair as needed.
Verify power and ground: backprobe TAC power and ground pins with key on. Repair high-resistance feeds or grounds before replacing modules.
Test CAN bus integrity: measure CANH/CANL voltages at multiple nodes with key on. Check for correct termination resistance (~60 Ω across CANH/CANL) and continuity between modules. Repair wiring faults.
Monitor live data: with the engine running or key on as required, monitor throttle position and status messages. Look for drop-outs, implausible values, or untranslated signals.
Reproduce under conditions: wiggle wiring harness while monitoring messages to find intermittent faults.
Software and compatibility check: verify TAC module calibration/programming matches vehicle VIN and software level. Reflash or reprogram per manufacturer procedures if required.
If wiring, power, grounds, and programming are confirmed good but invalid data persists, consider replacing the TAC module. After replacement, program/configure per factory procedure and verify proper operation.
If replacement does not clear the fault, suspect ECM or another network node sending bad data and expand diagnostics to other modules.

Likely causes

Intermittent or open CANH/CANL between ECM and TAC module
TAC module supply voltage low or ground high-resistance
Water intrusion or corrosion at TAC module connector
TAC module internal failure producing invalid telemetry
Module coding/programming incorrect after replacement or update

Fault status

⚠️ Status

Invalid data received from Throttle Actuator Control module — indicates a communication or module fault (CAN bus, wiring, power/ground, or module software/operation issue).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours

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U0408 — Invalid Data Received From Throttle Actuator Control Module