P1128 - CLOSED LOOP FUELING NOT ACHIEVED - BANK 1
P1129 - CLOSED LOOP FUELING NOT ACHIEVED - BANK 2
When Monitored:
Engine running in closed loop mode.
Set Condition:
Enable conditions are met and the 02 sensor has not been in closed loop control at least once on each of the two consecutive trips, the MIL illuminates and the DTC is set. Two Trip Fault. Three good trips to turn off the MIL
Possible Causes
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SIGNAL CIRCUIT
O2 RETURN CIRCUIT
O2 SENSOR HEATER OPERATION
O2 SENSOR
MAP SENSOR OPERATION
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR (HIGH)
PCM