Notes on Emissions Testing

1. Twelve cylinder engines through 1989 model year, are equipped with a closed-loop cut out circuit which allows the engine to be in closed-loop feedback control only when the transmission is in gear. When the transmission is placed into "park" or "neutral", the engine will go into open loop and run richer, in most instances rich enough to fail the tail pipe emissions test.

2. Before attempting to test the emissions on a V12 model, remove trim panel on the passenger side of the trunk. Below the ECU, there will be two red multi-plugs, one with two wires and a jumper. The other has four wires with a cap. Disconnect the jumper connection from the two wire red connector.

3. The vehicle will now stay in closed-loop in all cases during the emissions test.