U1187 SCP Communication Data Integrity Fault
The U1187 code indicates a data integrity issue on the SCP (Standard Corporate Protocol) network, which uses the SAE J1850 PWM physical layer common in Ford vehicles. Unlike a total bus failure, this code means that a receiving module (such as the PCM, BCM, or a body module) has detected invalid or missing data for a specific Primary Identifier within a transmitted message. The bus is active, but the data frame for that particular identifier is corrupted, incomplete, or does not match the expected format. This is often caused by electrical interference, intermittent voltage drops, or internal corruption in the transmitting module.
1. Commonly Affected Makes
2. Most Common Causes
- Short circuit to ground or voltage on the SCP bus wiring
- Faulty transmitting control module with internal communication issues
- Corroded or loose terminals in module connectors
- Electromagnetic interference (EMI) corrupting the J1850 signal
- Intermittent voltage drops in the power supply to the transmitting module
- Incorrect software update or calibration incompatibility between modules
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Intermittent or complete loss of function from affected module (e.g., gauges, climate control, power windows)
4. Step-by-Step Diagnosis
Scan for all stored codes and freeze frame data to identify the affected module and Primary Id
Visually inspect SCP bus wiring and connectors for damage, corrosion, or shorts
Check power and ground circuits at the transmitting module for voltage drops
Perform a network integrity test using a scope or scan tool to look for signal corruption
If wiring is good, suspect the transmitting module; try swapping or reprogramming if possible
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, but you may experience intermittent loss of some features. The vehicle will likely remain drivable, but have the issue diagnosed soon to prevent further problems.
How much does it cost to fix?▼
Diagnosis typically costs $100-$200. Repair costs vary widely: a simple wiring repair may be $100-$300, while replacing a module can range from $300 to $1,000+ including labor.