X55 - ACPSW PID "Closed" With ACPSW Disconnected

- Key Off.

- ACPSW disconnected.

- Disconnect Scan Tool from DLC.

- Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.

- Install breakout box, leave PCM disconnected.

- Measure resistance between Test Pin 86 (ACPSW) and Test Pins 77 and 103 (PWR GND).

- Are both resistances greater than 10,000 ohms?

YES -- REPLACE PCM. REMOVE breakout box. RECONNECT all components. RE-EVALUATE symptom.

NO -- SERVICE ACPSW circuit short to ground. REMOVE breakout box. RECONNECT all components. RE-EVALUATE symptom.