U1153 SCP Bus Communication Failure
The U1153 code indicates a communication fault on the SCP (Standard Corporate Protocol) bus, which is based on the SAE J1850 VPW standard. Specifically, the module that stored the code has detected invalid data or the complete absence of a message identified as 'Experimental #3' for a calibrated period. This bus interconnects modules such as the PCM, instrument cluster, ABS module, and GEM (Generic Electronic Module).
1. Commonly Affected Makes
2. Most Common Causes
- Open circuit, short to ground, or short to battery on the SCP (+) or SCP (-) lines
- Faulty module that transmits the 'Experimental #3' message (commonly the PCM or instrument cluster)
- Internal communication failure in the receiving module
- Damaged or missing bus termination resistors
- Low battery voltage causing module resets during communication
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Intermittent or complete loss of communication with certain modules, such as the instrument cluster or ABS
4. Step-by-Step Diagnosis
Scan all modules for related communication codes and check for low battery voltage.
Inspect the SCP bus wiring for opens, shorts, or damage, and verify termination resistors (typically 120 ohms each).
Use a lab scope or bus analyzer to monitor SCP bus activity and look for missing or corrupted 'Experimental #3' messages.
If wiring and termination are good, isolate the fault by disconnecting modules one at a time to identify the defective module.
5. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but you may experience intermittent communication issues with critical systems like ABS or the instrument cluster. It is recommended to diagnose and repair the fault promptly to avoid potential safety concerns.
How much does it cost to fix?▼
The cost can range from $100 to $500 depending on the root cause. Simple wiring repairs may be under $200, while replacing a module like the PCM or instrument cluster can cost $300–$500 or more.