No Communication with PCM in 2004 Infinity - Troubleshooting Guide
If your 2004 Infinity is showing no communication with the Powertrain Control Module (PCM), follow these step-by-step troubleshooting steps to identify and resolve the issue. 1. Perform a basic diagnostic test using a different OBD-II scanner. A faulty or incompatible scanner may falsely indicate no communication. 2. Check for 12V power at the ALDL (Alternator Learning Device) cavity #16 on the vehicle's wiring harness. This is a critical voltage supply required for PCM operation. 3. Determine the current vehicle status: - Is the engine running with the Check Engine Light (CEL) illuminated? - Is the vehicle operating normally and only checking codes? - Is the engine not running at all, or experiencing poor performance without a CEL? If these simple checks do not resolve the issue, further investigation into wiring, ground connections, or PCM failure may be required. Always ensure proper diagnostic procedures are followed before assuming hardware failure.
First, try a different OBD-II scanner to rule out scanner-related issues. Then, verify if there is 12V power at ALDL cavity #16 — this is essential for PCM communication. If both of these checks fail, confirm the vehicle's current status: running with CEL on, operating normally during code checks, not running at all, or experiencing poor performance without a CEL.