Corroded or damaged wiring or connectors at the ride level control module; Faulty ride height sensor or sensor wiring sending implausible data; Low battery voltage or poor grounds affecting module communication; Failed ride level control module; Network bus wiring fault (CAN or other protocol) between modules; Water intrusion into the ride level module or connector; Aftermarket accessories tapping into the network wiring

DTC codes / U04xx · Invalid data received from a module / U0421

U0421Invalid Data Received From Ride Level Control Module

Q: What does code U0421 mean?

Invalid Data Received From Ride Level Control Module. U0421 means the vehicle's main network gateway or engine control computer received data from the ride level control module that it judged invalid or out of range. The ride level module is responsible for monitoring and adjusting suspension height, and when its messages are corrupt or missing, the receiving module sets this communication fault.

U0421 means the vehicle's main network gateway or engine control computer received data from the ride level control module that it judged invalid or out of range. The ride level module is responsible for monitoring and adjusting suspension height, and when its messages are corrupt or missing, the receiving module sets this communication fault.

SystemNetwork

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaInvalid data received from a module

Symptoms you may notice

Often no symptoms besides the warning light, especially if the fault is intermittent
Ride height may be stuck at one level or the vehicle may sit unevenly
Suspension warning or ride control light illuminated on the dashboard
The ride level control module may not respond to height adjustment commands
Other unrelated warning lights may appear if the network bus is disturbed

Common causes, most likely first

Corroded or damaged wiring or connectors at the ride level control module
Faulty ride height sensor or sensor wiring sending implausible data
Low battery voltage or poor grounds affecting module communication
Failed ride level control module
Network bus wiring fault (CAN or other protocol) between modules
Water intrusion into the ride level module or connector
Aftermarket accessories tapping into the network wiring

How to diagnose and fix it

Check battery voltage and condition, and load-test the charging system
Inspect the ride level control module connectors for corrosion, water, or loose pins
Scan all modules for related codes and check live data from the ride level module
Perform a voltage drop test on the module's power and ground circuits
Check network bus wiring for shorts, opens, or excessive resistance
Test ride height sensors and their wiring for plausible signals
If all external checks pass, replace and reprogram the ride level control module

Before you replace the ride level module

A weak battery or failing alternator often causes invalid data codes on multiple modules, so always verify charging system health first.
Corroded grounds near the suspension components are a common hidden cause that mimics a failed module.
The code can be set by a faulty ride height sensor even though the sensor itself has no dedicated code, because its implausible signal corrupts the module's data.
Aftermarket suspension modifications or wiring taps can introduce noise on the network bus and trigger U0421 without any hard failure.
Intermittent U0421 that clears after a key cycle often points to a wiring harness chafe rather than a defective module.

Can I keep driving with U0421?

The vehicle is generally safe to drive if the suspension remains at a stable height, but avoid high-speed cornering or heavy loads until repaired. If the vehicle sits unevenly or the suspension is bottomed out, limit driving to low speeds and seek service promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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