What Does U1187 Mean?
Another Primary ID data communication failure on the SCP J1850 network. This code indicates yet another module or specific Primary ID parameter is invalid or not being received, suggesting widespread network issues or multiple module failures.
Common Causes
35%
Multiple module communication failure or complete SCP bus failure affecting all Primary ID messages
30%
Primary transmitting module (PCM or BCM) completely offline or failed
20%
Severe corrosion or water intrusion in main network harness connectors
15%
Electrical short or module pulling down entire network bus voltage
Diagnostic Steps
1
Step 1: Review all U-codes together (U1182, U1183, U1186, U1187) to identify pattern of communication failures
2
Step 2: Check if any modules are completely non-responsive or unable to communicate at all
3
Step 3: Measure SCP bus voltage and resistance with modules connected and disconnected to find shorts
4
Step 4: Inspect main underhood and underdash harness connectors for widespread corrosion or damage
5
Step 5: Perform systematic module disconnection to isolate which module may be causing bus failure if present
Estimated Repair Cost
$200 - $1,500
Parts + labor, varies by vehicle and location
Another Primary ID data communication failure on the SCP J1850 network. This code indicates yet another module or specific Primary ID parameter is invalid or not being received, suggesting widespread network issues or multiple module failures.
The most common cause of U1187 (SCP (J1850) Invalid or Missing Data for Primary Id) is: Multiple module communication failure or complete SCP bus failure affecting all Primary ID messages
Typical repair costs for U1187 range from $200 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Multiple Primary ID failures can result in loss of essential vehicle functions including instrument cluster, warning systems, and coordination between major control modules. Verify vehicle is safe to operate.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U1187 to identify the root cause.
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Quick Info
Category
Network
System
Vehicle Communication Network
Difficulty
Type
Manufacturer
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