OBD-II Fault Code

U1203: SCP (J1850) Invalid or Missing Data for Windows

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for U1203.

System family

Network

Manufacturer-specific

Repair category

Network / communication

Use this category to narrow your checks before replacing parts.

Severity

High

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What U1203 usually means

SCP (J1850) Invalid or Missing Data for Windows.

Common symptoms

Multiple warning lights or modules not communicating

Likely causes

Low battery voltage; Blown module fuse; Poor ground; Open/short on communication bus; Module offline

Diagnostic checks

Check battery condition, module fuses, grounds and network connectors before replacing modules; Run a full system scan to identify modules not responding; Inspect CAN/SCP wiring, connectors and grounds

Repair guidance

Repair power/ground or network wiring fault first; Only consider module replacement after wiring and power supply checks pass

Verification after repair

Rescan all modules and confirm communication returns

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary; Manufacturer-specific: confirm definition and test steps in the vehicle service manual. A DTC identifies a circuit or system condition, not always the failed part.