What Does U1120 Mean?
This code represents another missing primary identifier message on the SCP network. Multiple sequential U-codes (U1118-U1124) strongly suggest a systemic network failure rather than individual module issues.
Common Causes
40%
Complete network bus failure due to short to ground or short to power
25%
Central gateway module or BCM failure affecting entire network
20%
Widespread corrosion at central connector affecting multiple circuits
15%
Recent service or repair damaging network wiring
Diagnostic Steps
1
Step 1: Check for recent repair work that may have damaged wiring; inspect areas near recent service
2
Step 2: Locate and inspect central network junction points for physical damage or water intrusion
3
Step 3: Measure resistance between SCP+ and SCP- terminals (should be 100-120 ohms with all modules connected)
4
Step 4: Check for short to ground or power on both SCP+ and SCP- circuits (should show infinite resistance to ground/power)
5
Step 5: If wiring tests good, test BCM/gateway module power and ground circuits before condemning module
Estimated Repair Cost
$200 - $1,500
Parts + labor, varies by vehicle and location
This code represents another missing primary identifier message on the SCP network. Multiple sequential U-codes (U1118-U1124) strongly suggest a systemic network failure rather than individual module issues.
The most common cause of U1120 (SCP (J1850) Invalid or Missing Data for Primary Id) is: Complete network bus failure due to short to ground or short to power
Typical repair costs for U1120 range from $200 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Multiple system malfunctions likely including instrument cluster, lighting controls, and potentially engine performance. Safe for limited driving to repair facility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U1120 to identify the root cause.
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Quick Info
Category
Network
System
Vehicle Communication Network
Difficulty
Type
Manufacturer
Recommended Tools
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