What Does U1223 Mean?
The communication network is not receiving valid data from the module responsible for interior lighting control. This indicates a breakdown in the SCP (Standard Corporate Protocol) J1850 bus communication specific to interior lamp status messages.
Common Causes
35%
Faulty lighting control module (LCM) or body control module (BCM)
30%
Damaged or corroded wiring in the SCP bus network between modules
20%
Poor ground connection at lighting control module
15%
Failed interior lamp switch or dimmer module
Diagnostic Steps
1
Step 1: Monitor live data stream for interior lamp module communication status on scan tool
2
Step 2: Inspect SCP bus network wiring harness for damage, chafing, or corrosion at connectors
3
Step 3: Test voltage and continuity on SCP bus lines (typically 2-wire network) between modules
4
Step 4: Check ground connections at lighting control module and BCM for resistance
5
Step 5: Substitute or reflash lighting control module if all wiring and grounds test good
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
The communication network is not receiving valid data from the module responsible for interior lighting control. This indicates a breakdown in the SCP (Standard Corporate Protocol) J1850 bus communication specific to interior lamp status messages.
The most common cause of U1223 (SCP (J1850) Invalid or Missing Data for Interior Lamps) is: Faulty lighting control module (LCM) or body control module (BCM)
Typical repair costs for U1223 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Interior lighting functions may be compromised, affecting visibility during night driving. Vehicle remains safe to drive but convenience features may be affected.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U1223 to identify the root cause.
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Quick Info
Category
Network
System
Body Control Network
Difficulty
Type
Manufacturer
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