U1126: SCP Bus Data Fault
Diagnostic trouble code U1126 indicates that a control module has detected missing or invalid data on the SCP (Standard Corporate Protocol) J1850 communication bus, specifically for the primary data identifier. The SCP J1850 bus is a Ford-developed serial communication network operating at 41.6 kbps with pulse-width modulation. This code sets when a receiving module fails to receive expected data from another module, or the data is corrupt or does not conform to the protocol's message format. The primary ID refers to the main message identifier that defines the type of data being transmitted, such as vehicle speed, temperature, or system status.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty transmitting control module not sending correct data on the SCP J1850 bus
- Electromagnetic interference or noise on the SCP communication bus
- Abnormal resistance in the SCP bus wiring (OBD-II pins 2 and 10)
- Poor connections or corrosion at communication bus splice points
- Internal failure of the receiving control module misinterpreting data
- SCP bus voltage out of specified range (0V to 5V logic, 7.5V average line voltage)
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Intermittent or complete loss of communication between modules, affecting gauges, transmission shifting, or other systems
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data to identify related modules
Inspect SCP bus wiring at OBD-II pins 2 and 10 for damage, corrosion, or shorts
Measure bus voltage and resistance; typical values: 0V-5V logic, 7.5V average, 60 ohms termination resistance
Check for electromagnetic interference from nearby components like alternators or ignition systems
Perform a network test to isolate the faulty module by disconnecting modules one at a time
5. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but you may experience drivability issues or warning lights. It is recommended to diagnose and repair promptly to avoid potential communication failures affecting critical systems.
How much does it cost to fix?▼
Repair costs vary widely depending on the root cause. Simple wiring repairs may cost $100-$200, while replacing a control module can range from $300 to $1,000 or more, including labor and programming.