P1128-CLOSED LOOP FUELING NOT ACHIEVED - BANK 1

For a complete wiring diagram Refer to Section 8W.



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

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).



Diagnostic Test

1. ACTIVE DTC

Diagnose all other trouble codes before continuing.
Start the engine.
Allow the engine to reach normal operating temperature.
With a scan tool, select View DTCs.

NOTE: 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?

Yes


No

2. CHECKING FUEL PRESSURE

WARNING: 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 a scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.

NOTE: 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 Specification


Above Specification


Below Specification

3. O2 SENSOR OPERATION

Start the engine.
Allow the engine to reach normal operating temperature.

NOTE: 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.


NOTE: 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.


NOTE: 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 a scan tool, monitor all of the O2 Sensor voltage readings.

Is the voltage switching between 2.5 and 3.4 volts for all the O2 Sensors?

Yes


No

4. 1/1 O2 SENSOR HEATER OPERATION

Turn the ignition off.

NOTE: 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.


Ignition on, engine not running.
With a scan tool, actuate the 1/1 O2 Heater Test.
With the scan tool, monitor 1/1 O2 Sensor voltage for at least 2 minutes.

Does the voltage stay above 4.5 volts?

Yes


No

5. MAP SENSOR OPERATION

Turn the ignition off.
Connect a Vacuum Gauge to a Manifold Vacuum source.
Start the engine.
Allow the engine to idle.

NOTE: 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?

Yes


No

6. ECT SENSOR OPERATION

NOTE: For this test to be valid, the thermostat must be operating correctly.

NOTE: This test works best if performed on a cold engine (cold soak)


Ignition on, engine not running.
With a 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.

NOTE: If engine coolant temperature is above 82 degrees C (180 degrees F), allow the engine to cool until 65 degrees C (150 degrees 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 degrees C (180 degrees F). The value should reach at least 82 degrees C (180 degrees F).

Did the ECT value increase smoothly and did it reach at least 82 degrees C (180 degrees F)?

Yes


No

7. ENGINE MECHANICAL PROBLEM

Turn 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?

Yes


No

8. 1/1 O2 SENSOR



Ignition on, engine not running.
Disconnect the 1/1 O2 Sensor harness connector.
With a scan tool, monitor the 1/1 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 (K41) Signal circuit and the (K902) O2 Upstream Return circuit in the O2 Sensor harness connector.

NOTE: 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 with the jumper wire installed?

Yes


No

9. (K41) O2 SENSOR 1/1 SIGNAL CIRCUIT

With a scan tool, monitor the 1/1 O2 Sensor voltage reading with the jumper wire removed.

NOTE: 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.


NOTE: 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?

Yes


No

10. (K902) O2 UPSTREAM RETURN CIRCUIT



Disconnect the 1/1 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?

Yes


No

11. PCM

NOTE: Before 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?

Yes


No

12. RESTRICTED FUEL SUPPLY LINE

WARNING: 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 a scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.

NOTE: Fuel pressure specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).



Is the fuel pressure within specification?

Yes


No

13. FUEL PUMP INLET STRAINER

WARNING: 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.


Turn the ignition off.
Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.

Is the Fuel Inlet Strainer plugged?

Yes


No

14. FUEL PUMP MODULE


If there are no possible causes remaining, view repair.

Repair