DR-4A Fault Code 21-Oxygen Sensor Circuit

Complete Driveability Test 1, Step A before proceeding.

1. With diagnostic read-out tool connected to engine test connector, place ignition switch in Off position.
2. Disconnect electrical connector from oxygen sensor, then place system in Sensor Test 02.
3. If display reading is at least .4 volt, proceed to Test 4 step B.
4. If display indicates zero volts, replace SMEC.
NOTE: Before replacing the SMEC, make sure the N11 black/dark green wire at cavity No. 23 of the SMEC 60-way connector is not shorted to ground.