OBD-II Fault Code

U1134: SCP (J1850) Invalid or Missing Data for Ignition Switch / Starter

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for U1134.

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 U1134 usually means

SCP (J1850) Invalid or Missing Data for Ignition Switch / Starter.

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.