What Does U1118 Mean?
The control module is not receiving valid data over the SCP (Standard Corporate Protocol) J1850 network bus for a primary identifier message. This indicates a communication breakdown between modules on the vehicle network.
Common Causes
35%
Failed or failing control module (PCM, BCM, or instrument cluster) not transmitting proper data
30%
Damaged or corroded wiring in the SCP bus circuit or poor module ground connections
20%
Low system voltage or weak battery causing communication errors
15%
Water intrusion or corrosion at module connector terminals
Diagnostic Steps
1
Step 1: Verify battery voltage is above 12.4V with key off and above 13.5V running; load test battery and charging system
2
Step 2: Inspect all module connectors for corrosion, bent pins, or moisture intrusion; clean and secure connections
3
Step 3: Use factory scan tool with network monitoring capability to identify which module is failing to communicate
4
Step 4: Check SCP bus wiring continuity and resistance between communicating modules (should be approximately 100-120 ohms)
5
Step 5: If specific module identified, check module power, ground circuits, and replace module if circuits test good
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
The control module is not receiving valid data over the SCP (Standard Corporate Protocol) J1850 network bus for a primary identifier message. This indicates a communication breakdown between modules on the vehicle network.
The most common cause of U1118 (SCP (J1850) Invalid or Missing Data for Primary Id) is: Failed or failing control module (PCM, BCM, or instrument cluster) not transmitting proper data
Typical repair costs for U1118 range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle may experience reduced functionality of various systems including gauges, warning lights, or driveability issues. Safe to drive short distances but should be diagnosed promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U1118 to identify the root cause.
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Quick Info
Category
Network
System
Vehicle Communication Network
Difficulty
Type
Manufacturer
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