U1042: SCP Bus Communication Failure with TCS/ABS
The U1042 code indicates a communication failure on the SCP (Standard Corporate Protocol) data bus, which is based on the SAE J1850 standard. Specifically, the powertrain control module (PCM) or the bus master module has detected that messages from the traction control system (TCS) or anti-lock brake system (ABS) module are missing, corrupted, or not in the correct J1850 format. This can be caused by wiring issues, a faulty TCS/ABS module, or other bus-related problems.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty traction control (TCS) or ABS module
- Open or short circuit in the SCP (J1850) bus wiring (both + and - circuits)
- Damaged or missing bus termination resistor
- Faulty PCM or bus master module
- Corroded or loose connections at data bus connectors
- Low voltage or power supply failure to the traction module
- Corrupted or outdated software in the traction module
3. Symptoms You Will Notice
- Illuminated ABS or traction control warning light
- Reduced traction control or ABS functionality
4. Step-by-Step Diagnosis
Scan for other related codes (e.g., U1041, U1043) to narrow down the issue.
Inspect the SCP bus wiring for damage, corrosion, or loose connections.
Check the termination resistor on the bus (typically 120 ohms) with a multimeter.
Test power and ground at the TCS/ABS module connector.
If wiring and power are good, suspect the TCS/ABS module or PCM; perform a module communication test.
5. Frequently Asked Questions
Is it safe to drive?▼
The vehicle may still be drivable, but ABS and traction control will likely be disabled. Braking performance may be affected in slippery conditions. It is recommended to have the issue diagnosed and repaired promptly.
How much does it cost to fix?▼
Costs vary widely depending on the root cause. A simple wiring repair may cost $100-$200, while replacing a TCS/ABS module can range from $300 to $800 or more, including labor.