What Does U1240 Mean?
The module cannot receive valid Primary ID data from the SCP bus. Primary ID typically contains critical vehicle identification or module identification information needed for proper network communication and module coordination.
Common Causes
35%
Failed body control module or powertrain control module not broadcasting ID
30%
Corrupted or damaged SCP bus wiring preventing ID transmission
20%
Loss of power or ground to primary transmitting module
10%
Module programming corruption or loss of stored configuration
5%
Bus contention or electrical short causing data corruption
Diagnostic Steps
1
Step 1: Identify which module is setting U1240 and which module should be transmitting Primary ID
2
Step 2: Verify power and ground at the transmitting module using multimeter
3
Step 3: Check for additional communication codes that indicate complete module failure
4
Step 4: Monitor SCP bus with scan tool or oscilloscope to verify network activity and signal quality
5
Step 5: Test or replace suspected transmitting module if power, ground, and wiring are confirmed good
Estimated Repair Cost
$200 - $900
Parts + labor, varies by vehicle and location
The module cannot receive valid Primary ID data from the SCP bus. Primary ID typically contains critical vehicle identification or module identification information needed for proper network communication and module coordination.
The most common cause of U1240 (SCP (J1850) Invalid or Missing Data for Primary Id) is: Failed body control module or powertrain control module not broadcasting ID
Typical repair costs for U1240 range from $200 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Moderate concern. Loss of Primary ID data may affect multiple vehicle systems coordination, potentially impacting anti-theft, starting, or accessory functions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U1240 to identify the root cause.
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Quick Info
Category
Network
System
Body Control / Network Communication
Difficulty
Type
Manufacturer
Recommended Tools
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