U1147 PCM-PATS Communication Failure
The U1147 code is a manufacturer-specific network communication fault indicating that the Powertrain Control Module (PCM) is receiving invalid or null data from the Passive Anti-Theft System (PATS) module over the Standard Corporate Protocol (SCP) bus based on SAE J1850. This prevents proper immobilizer validation, affecting key authentication and potentially preventing the engine from starting.
1. Commonly Affected Makes
2. Most Common Causes
- Loss of communication with the PATS module
- Unprogrammed ignition key or damaged transponder
- Open or short circuit in the SCP (J1850) bus wiring
- Corroded or loose electrical connections at the security module
- Faulty PATS module
- Internal failure in the Powertrain Control Module (PCM)
3. Symptoms You Will Notice
- Engine cranks but does not start
- Security light flashing or staying on
- No communication with PATS module during scan
4. Step-by-Step Diagnosis
Scan for all stored codes and verify U1147 is present
Inspect SCP bus wiring for opens, shorts, or corrosion
Check PATS module power and ground circuits
Test key transponder functionality and programming
Attempt communication with PATS module using a professional scan tool
If all else fails, test PCM for internal faults
5. Frequently Asked Questions
Is it safe to drive?▼
No, the vehicle may not start or may stall unexpectedly due to the immobilizer fault, posing a safety risk.
How much does it cost to fix?▼
Repair costs typically range from $100 to $600, depending on whether the issue is a simple wiring repair, key programming, or module replacement.