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Home >> Jeep >> 2024 >> Grand Cherokee Summit >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 79 (2.0L - DTCS P0A14 To P1206) >> DTC Troubleshooting >> P1128-Closed Loop Fueling Not Achieved - Bank 1 Upstream >> Possible Causes

Possible Causes

WARNING: This page is about a different variant/trim than selected.
Possible Causes
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
O2 SENSOR HEATER OPERATION
O2 SIGNAL CIRCUIT
O2 RETURN CIRCUIT
O2 SENSOR
ECT SENSOR OPERATION
ENGINE MECHANICAL PROBLEM
FUEL FILTER/PRESSURE REGULATOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding. Refer to  PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE  .