U0408

Code

Generic U — Network/User

Invalid Data Received From Throttle Actuator A Control Module

Brand: Generic

Type: U — Network/User

Views: UK: 30 EN: 52 RU: 28

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Page language: EN

Causes

Faulty Throttle Actuator A control module (hardware or firmware)
CAN/LIN bus communication fault (open, short, high resistance, missing termination)
Damaged or corroded wiring or connectors between PCM and throttle actuator module
Low battery voltage or intermittent power/ground to the throttle module
Software mismatch or calibration/programming error after module replacement or update
Electromagnetic interference or network message collision

Symptoms

Malfunction Indicator Lamp (MIL) on
Reduced engine power / limp-home mode
Poor or unresponsive throttle/acceleration
Unexpected throttle behavior (jerking, surging, stuck position warnings)
Possible inability to start if throttle control is disabled
Other communication-related DTCs present

What to check

Read and record all stored DTCs and freeze frame data with a capable scan tool
Check battery voltage and charging system; verify stable supply (12V) during start/crank and while scanning
Visually inspect wiring and connectors at the throttle actuator module and related harness for damage, corrosion, or water intrusion
Scan for CAN/LIN network status and message counters; check for bus-off or error frames
Check for related DTCs in PCM, TAC, and other modules that share the same bus
Use a scope or bidirectional scan tool to verify presence and integrity of throttle actuator messages (CAN/LIN) on the bus

Signal parameters

Throttle position sensor A: expected 0–100% (or 0–5 V for analog sensors) and matching secondary sensor
Commanded throttle angle / actuator position: plausible range per vehicle spec (e.g., 0–100%)
Throttle actuator status flags: valid bits and checksum where used
CAN/LIN message ID for throttle actuator: present at expected frequency (e.g., 10–100 Hz) without corruption
Bus datarate: matches vehicle specification (commonly 250 kbps or 500 kbps for CAN)
Message timing/jitter: consistent periodic transmission; no unexpected gaps or repeats

Diagnostic algorithm

Connect a factory-level or capable aftermarket scan tool. Record all codes and freeze frame data. Note related communication codes.
Verify battery voltage (should be within specification) and good grounds. Recharge or replace battery if low; ensure stable supply during testing.
Visually inspect throttle actuator connectors and wiring for physical damage, corrosion, or moisture. Disconnect and inspect pins for bent/corroded terminals.
Check for presence of throttle actuator CAN/LIN messages using the scan tool or oscilloscope. Confirm message ID, frequency, payload plausibility, and absence of bus errors.
If messages are missing or corrupted, isolate the bus: disconnect other modules (where safe) or use wiring diagrams to find breaks/shorts. Measure continuity and resistance to ground/battery on suspect wires.
Perform a wiggle/strain test on wiring and connectors while monitoring live data to reproduce intermittent faults.
If power/ground to the throttle actuator module is suspect, back-probe and verify proper supply voltage and ground reference with key ON and engine running (if safe to do so).
If wiring and bus integrity are good and the module still sends invalid data, check for available software updates or known service bulletins. Reflash or reprogram the throttle actuator module and PCM per manufacturer procedure if required.
Replace the throttle actuator control module only after confirming wiring, power, grounds, and bus are good. After replacement or reprogramming, clear codes and perform a road test and network scan to confirm the repair.
If fault persists after module replacement and wiring checks, investigate other modules on the same network for malformed messages or intermittent failures.

Likely causes

Loose, corroded or damaged connector at the throttle actuator module
Intermittent power or ground to the throttle actuator module (voltage drop or return path high resistance)
Broken or shorted CAN/LIN wiring, missing termination resistor, or bus short to battery/ground
Failed throttle actuator control module (internal processor, memory, or firmware corruption)
Incorrect or incomplete module software calibration after service or replacement
Other module sending malformed/corrupt messages on the same network

Fault status

⚠️ Status

U0408 — Invalid Data Received From Throttle Actuator A Control Module. The PCM detected received data from the throttle actuator module that failed plausibility/format checks or was corrupted. This is a communications or data integrity fault; additional codes, freeze frame, and message diagnostics are required before replacing modules.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours