OBD-II Diagnostic Trouble Code
U0403 — Invalid Data Received From Cruise Control Module
U0403 means a module received invalid data from the cruise control module. The message arrived but the cruise status, set speed or switch data was out of range or implausible. On many trucks cruise functions are handled inside the engine or cab controller, so how this code is defined depends on the manufacturer.
Severity 2/5
Truck-relevant
Service soon
Severity
Service soon
Invalid Data Received From Cruise Control Module
Code
U0403
Category
Network
Subsystem
Network
Truck-relevant
Yes
What this means for truckers
U0403 (Invalid Data From Cruise Module) — cruise module data malformed.
Before you replace parts — try this first
U0403 on the Network system is most often faulty cruise switch or steering wheel clock spring giving invalid inputs — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Cruise control will not engage or drops out, and cruise indicators may behave strangely. The engine and transmission otherwise work normally.
Common causes
- CommonFaulty cruise switch or steering wheel clock spring giving invalid inputs ($100–$500)
- OccasionalWiring or connector fault in the cruise switch circuit ($100–$400)
- RareCruise module software issue or failure ($300–$1200)
How to fix
Check cruise switch inputs on a scan tool while operating each switch
When to use: First step
Inspect the clock spring and switch wiring
When to use: When switch readings are erratic
Update or replace the cruise control module
When to use: After the switch inputs and wiring are verified
Affects most
- RAM 35001 complaint mention this code
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → U0401 — Invalid Data Received From ECM/PCM A
- → U0402 — Invalid Data Received From TCM
- → U0404 — Invalid Data Received From Gear Shift Control Module
- → U0415 — Invalid Data Received From ABS Control Module
- → U0418 — Invalid Data Received From Brake System Control Module
- → Complaints on RAM 3500
Frequently Asked Questions
Can I drive with code U0403?
U0403 is severity 2 — service this week. Not an immediate stop, but ignoring it usually compounds the problem. Most common cause for this code is a worn sensor or minor performance fault that won't strand you today but will get more expensive the longer you wait.
How much does it cost to fix U0403 on a commercial truck?
Total repair cost ranges $100–$1200 depending on the root cause. The cheapest fix is usually the first one listed below — Faulty cruise switch or steering wheel clock spring giving invalid inputs — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will U0403 fail a DOT inspection?
U0403 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between U0403 and related codes?
U0403 is closely related to: U0401 (Invalid Data Received From ECM/PCM A), U0402 (Invalid Data Received From TCM), U0404 (Invalid Data Received From Gear Shift Control Module), U0415 (Invalid Data Received From ABS Control Module). These codes share the same subsystem (network) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only U0403 is set without the companions, the issue is more isolated.
How do I prevent U0403 from coming back after a repair?
For U0403 (Invalid Data Received From Cruise Control Module), prevention centers on the network system. Pay attention to ground connections at every PM — bad grounds are 70% of communication codes. Inspect harness routing for chafe points. Don't disconnect modules with the key on.