Ford SCP Bus Communication Fault U1223
The U1223 code indicates a communication failure on the Ford-specific SCP (J1850) network, where the receiving module detects invalid or missing data from the interior lamp control module. This means the interior lighting module is not transmitting the expected information over the data bus, or the data sent contains format errors that violate the protocol standard. Technically, this code is set when there is a data frame interruption or an electrical fault preventing the interior lights module from properly communicating with the main control module or diagnostic tool. It does not represent a direct mechanical failure of the bulbs but rather a network communication issue or an internal fault in the transmitting module.
1. Commonly Affected Makes
2. Most Common Causes
- Damaged or internally shorted interior lamp control module (Lamp Out Module)
- SCP (J1850) bus wiring shorted to ground or voltage
- Corroded, bent, or poor contact pins in the lighting module connectors
- Open or out-of-spec SCP bus termination resistor
- Loss of power (B+) or ground (GND) to the interior lights module
- Internal failure in the main control module (PCM or central module) when processing the data frame
3. Symptoms You Will Notice
- Interior lights may not operate correctly or at all
- Check Engine Light or other warning lights may illuminate
4. Step-by-Step Diagnosis
Scan for additional codes and verify U1223 is present
Inspect the interior lamp control module and its connectors for damage, corrosion, or loose pins
Check the SCP bus wiring for shorts, opens, or high resistance
Test the bus termination resistor for proper resistance (typically 120 ohms)
Verify power and ground supply to the interior lights module
If all else fails, replace the interior lamp control module
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive with this code as it does not affect critical drivetrain or safety systems. However, interior lights may not work properly.
How much does it cost to fix?▼
The cost can range from $50 to $200 for diagnosis and repair, depending on the root cause. Replacing the interior lamp module typically costs $100-$300 including parts and labor.