U1794 SCP Bus Communication Failure
The U1794 code indicates a communication fault on the SCP (Standard Corporate Protocol) data bus, which is Ford's proprietary J1850-based network operating at 41.6 kbps. Specifically, this code points to a 'Lack of Acknowledgment' condition involving the mirror control module. This means the master module (typically the GEM or mirror module) did not receive an acknowledgment from the mirror control module within the expected time, or the mirror module failed to respond. This can affect power adjustment, heating, folding, or turn signal functions of the mirrors, depending on vehicle configuration.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty mirror control module (driver or passenger side)
- Open or short circuit in the SCP bus wiring (SCP+ and SCP- circuits)
- Incorrect bus termination resistance (should be approximately 120 ohms on J1850)
- Corrosion in mirror or module connectors
- Weak battery or voltage fluctuations disrupting bus communication
3. Symptoms You Will Notice
- Power mirrors not adjusting
- Mirror heating or folding inoperative
- Mirror turn signals not working
- Possible multiple communication codes or warning lights
4. Step-by-Step Diagnosis
Scan for all codes and check for related U-codes
Inspect SCP bus wiring for shorts, opens, or corrosion
Measure bus termination resistance at the mirror module connector (should be ~120 ohms)
Test mirror module power and ground circuits
Check GEM module for faults or communication issues
Perform a network test to verify bus communication integrity
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle is generally safe to drive, but mirror functions may be limited or inoperative. Have the issue diagnosed soon to prevent further electrical problems.
How much does it cost to fix?▼
Repair costs typically range from $100 to $600, depending on whether the issue is a wiring repair, connector cleaning, or module replacement.