DR-4B Oxygen Sensor Circuit at Logic Module

*** UPDATED BY TSB #18-61-86

1. With oxygen sensor disconnected, turn ignition switch Off.
2. Connect a digital voltmeter to cavity 18 of blue connector and ground, then turn ignition switch to Run position.
3. If voltmeter reads at least .4 (4 tenths) volts, locate and repair open circuit in wire of cavity 18 to oxygen sensor.
4. If voltmeter reading is zero, replace logic module.
CAUTION: Before replacing the logic module check the terminal in cavity No. 18 of the blue connector to make sure it is not crushed causing a poor connection.