U1133 SCP Communication Fault
The U1133 code indicates that a control module has detected a failure in the SCP (Standard Corporate Protocol, also known as J1850 PWM/VPW) communication bus related to vehicle motion data. This proprietary network is primarily used by Ford Motor Company. The code specifically means that messages containing vehicle motion status—typically from the ABS module, wheel speed sensors, or traction control module—are missing, corrupted, or invalid as expected by the receiving module. Per SAE J2012, U1xxx codes are manufacturer-specific data network communication issues.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty ABS or traction control module that generates motion data
- Open or short circuit in the SCP (J1850) bus wiring between modules
- Faulty wheel speed sensor or vehicle speed sensor
- Defective receiving module (PCM, instrument cluster, etc.)
- Incorrect bus termination on the SCP network
- Corrosion or damage in communication bus connectors
- Low voltage or power failure in related modules
3. Symptoms You Will Notice
- Check Engine Light or ABS warning light illuminated
- Speedometer or odometer malfunction
- Traction control or ABS system inoperative
- Transmission shifting issues (if PCM relies on speed data)
4. Step-by-Step Diagnosis
Scan all modules for related communication codes and freeze frame data
Inspect SCP bus wiring and connectors for damage, corrosion, or shorts
Check wheel speed sensor operation and wiring integrity
Verify power and ground supplies to ABS, PCM, and instrument cluster
Test bus termination resistors (typically 120 ohms) at each end of the SCP network
If wiring is intact, isolate the faulty module by disconnecting modules one at a time while monitoring bus activity
5. Frequently Asked Questions
Is it safe to drive?▼
You can usually drive short distances, but safety systems like ABS and traction control may be disabled. Have it diagnosed soon to avoid further issues.
How much does it cost to fix?▼
Repair costs range from $100 for a simple wiring fix to $800+ if a module replacement is needed, depending on the root cause and labor rates.