P1129-CLOSED LOOP FUELING NOT ACHIEVED

P1129-CLOSED LOOP FUELING NOT ACHIEVED - BANK 2For a complete wiring diagram Refer to Section 8W.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 CausesRESTRICTED FUEL SUPPLY LINEFUEL PUMP INLET STRAINER PLUGGEDFUEL PUMP MODULEO2 SIGNAL CIRCUITO2 RETURN CIRCUITO2 SENSOR HEATER OPERATIONO2 SENSORMAP SENSOR OPERATIONECT SENSOR OPERATIONENGINE MECHANICAL PROBLEMFUEL FILTER/PRESSURE REGULATOR (HIGH)PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).Diagnostic Test1. ACTIVE DTCDiagnose all other trouble codes before continuing.Start the engine.Allow the engine to reach normal operating temperature.With a scan tool, select View DTCs.It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.Is the DTC Active or Pending at this time?YesGo To 2NoRefer to the INTERMITTENT CONDITION Diagnostic Procedure.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)2. CHECKING FUEL PRESSURE The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death. Install a fuel pressure gauge to the fuel rail.Ignition on, engine not running.With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.Fuel pressure specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).Turn the ignition off.Choose a conclusion that best matches your fuel pressure reading.Within SpecificationGo To 3Above SpecificationReplace the fuel filter/pressure regulator.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)Below SpecificationGo To 12 Stop All Actuations. 3. O2 SENSOR OPERATIONStart the engine.Allow the engine to reach normal operating temperature.If one of the O2 Sensor's Signal or Return circuit is shorted to ground the scan tool will display all O2 Sensor voltage readings low. The O2 Sensor that is shorted to ground will display a voltage reading near or at 0 volts.If one of the O2 Sensor Signal or Return circuits are shorted to voltage, the scan tool will display all O2 Sensor voltage readings high.After the repairs have been made, verify proper O2 Sensor operation. If all the O2 Sensor voltage readings have not returned to normal, follow the diagnostic procedure for the remaining O2 Sensors.With the scan tool, monitor the 2/1 O2 Sensor voltage reading.Is the voltage switching between 2.5 and 3.4 volts?YesGo To 4NoGo To 84. 2/1 O2 SENSOR HEATER OPERATIONTurn the ignition off.Wait a minimum of 10 minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize at 5.0 volts.Perform the following test on all O2 Sensors.Ignition on, engine not running.With a scan tool, actuate the 2/1 O2 Heater Test.With the scan tool, monitor 2/1 O2 Sensor voltage for at least 2 minutes.Does the voltage stay above 4.5 volts?YesReplace the 2/1 O2 Sensor.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 55. MAP SENSOR OPERATIONTurn the ignition off.Connect a Vacuum Gauge to a Manifold Vacuum source.Start the engine.Allow the engine to idle.If engine will not idle, maintain a constant RPM above idle.With the scan tool, read the MAP Sensor vacuum value.Is the scan tool reading within 1 inch of the Vacuum Gauge reading?YesGo To 6NoReplace the MAP Sensor.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)6. ECT SENSOR OPERATIONFor this test to be valid, the thermostat must be operating correctly.This test works best if performed on a cold engine (cold soak).Ignition on, engine not running.With the scan tool, read the Engine Coolant Temperature (ECT) Sensor value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.If engine coolant temperature is above 82° C (180° F), allow the engine to cool until 65° C (150° F) is reached.Start the Engine.During engine warm-up, monitor the ECT Sensor value. The temperature value change should be a smooth transition from start up to normal operating temperature 82° C (180° F). The value should reach at least 82° C (180° F).Did the ECT value increase smoothly and did it reach at least 82° C (180° F)?YesGo To 7NoReplace the Engine Coolant Temperature Sensor.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)7. ENGINE MECHANICAL PROBLEMTurn the ignition off.Check for any of the following conditions/mechanical problems.AIR INDUCTION SYSTEM - must be free from leaks.ENGINE VACUUM - must be at least 13 inches in neutral.ENGINE VALVE TIMING - must be within specifications.ENGINE COMPRESSION - must be within specifications.ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.ENGINE PCV SYSTEM - must flow freely.TORQUE CONVERTER STALL SPEED - must be within specifications.POWER BRAKE BOOSTER - no internal vacuum leaks.FUEL - must be free of contamination.FUEL INJECTOR - plugged or restricted injector; control wire not connected to correct injector.Are there any engine mechanical problems?YesRepair as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 118. O2 SENSOR

Ignition on, engine not running.Disconnect the 2/1 O2 Sensor harness connector.With the scan tool, monitor the 2/1 O2 Sensor voltage.O2 Sensor voltage should read 5.0 volts on the scan tool with the connector disconnected.Connect a jumper wire between the (K43) O2 Sensor 2/1 Signal circuit and the (K902) O2 Upstream Return circuit in the O2 Sensor harness connector.The voltage should drop from 5.0 volts to 2.5 volts with the jumper wire in place.Did the O2 Sensor voltage change from 5.0 volts to 2.5 volts when the jumper wire was installed?YesReplace the 2/1 O2 Sensor.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 9Remove the jumper wire before continuing.9. O2 SENSOR SIGNAL CIRCUITWith the scan tool, monitor all the O2 Sensor voltage reading with the jumper wire removed.The scan tool will display all O2 Sensor voltage readings approximately 5.0 volts when only one O2 Sensor's Signal circuit is shorted to voltage.The scan tool will display one O2 Sensor voltage close to zero and the others will read lower than normal when one O2 Sensor Signal circuit contains excessive resistance.Is the voltage above 4.8 volts?YesGo To 10NoCheck all the O2 Signal circuits for a short to ground, open, or short to voltage. Inspect the O2 Sensor connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module per Service Information.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)10. (K902) O2 UPSTREAM RETURN CIRCUIT

Disconnect the 2/1 O2 Sensor harness connector.Measure the voltage on the (K902) O2 Upstream Return circuit in the O2 Sensor harness connector.Is the voltage at 2.5 volts?YesGo To 11NoCheck the (K902) O2 Upstream Return circuit for a short to ground, open, or short to voltage. Inspect the O2 Sensor connector and the PCM harness connector. If OK, replace and program the Powertrain Control Module per Service Information.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)11. PCMBefore continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.Were there any problems found?YesRepair as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoReplace and program the Powertrain Control Module per Service Information.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)12. RESTRICTED FUEL SUPPLY LINE The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow these instructions can result in personal injury or death. Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module.Install special 5/16 fuel line adapter tool #6539 between disconnected fuel line and the fuel pump module.Attach a fuel pressure test gauge to the T fitting on tool #6539.Ignition on, engine not running.With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.Fuel pressure specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).Is the fuel pressure within specification?YesRepair or replace fuel supply line as necessary.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 13Stop All Actuations. 13. FUEL PUMP INLET STRAINERThe fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting or line, the fuel system pressure must be released.Turn the ignition off.Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.Is the Fuel Inlet Strainer plugged?YesReplace the Fuel Pump Inlet Strainer.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)NoGo To 1414. FUEL PUMP MODULEIf there are no possible causes remaining, view repair.RepairReplace the Fuel Pump Module.Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)