What Does U1246 Mean?
Communication failure on the SCP J1850 network regarding Primary ID data transmission. A primary control module is not broadcasting its identification or status data correctly on the network.
Common Causes
30%
Powertrain Control Module (PCM) communication fault or initialization error
25%
Body Control Module (BCM) failure to initialize or broadcast primary identification
20%
SCP bus wiring short circuit, open circuit, or cross-talk interference
15%
Loss of power or ground to primary control module during boot sequence
10%
Module software corruption or failed programming requiring reprogramming
Diagnostic Steps
1
Step 1: Identify which module is designated as Primary ID transmitter using manufacturer-specific documentation
2
Step 2: Check power and ground circuits to the primary module (typically PCM or BCM) during key-on initialization
3
Step 3: Use scan tool to attempt communication with all modules and document which respond and which do not
4
Step 4: Measure SCP bus voltage and resistance values to verify network integrity and proper termination
5
Step 5: Attempt to reprogram or reflash the primary module if hardware tests pass but communication remains faulty
Estimated Repair Cost
$200 - $1,200
Parts + labor, varies by vehicle and location
Communication failure on the SCP J1850 network regarding Primary ID data transmission. A primary control module is not broadcasting its identification or status data correctly on the network.
The most common cause of U1246 (SCP (J1850) Invalid or Missing Data for Primary Id) is: Powertrain Control Module (PCM) communication fault or initialization error
Typical repair costs for U1246 range from $200 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May cause reduced engine performance, transmission issues, or multiple system malfunctions. Drive cautiously and seek service promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U1246 to identify the root cause.
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Quick Info
Category
Network
System
Network Communication / Primary Control Modules
Difficulty
Type
Manufacturer
Recommended Tools
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