FixVault

Possible Causes

Possible Causes 
(K399) O2 2/2 HEATER CONTROL CIRCUIT OPEN
(Z42) O2 2/2 HEATER GROUND CIRCUIT OPEN
2/2 O2 SENSOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding.