P1128

P1128 - CLOSED LOOP FUELING NOT ACHIEVED - BANK 1

For complete wiring diagrams refer to Diagrams/Electrical.


- 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







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

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

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition


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

- Go To 3

Above Specification

- Replace the fuel filter/pressure regulator.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

Below Specification

- Go To 12

CAUTION: Stop All Actuations.

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

- Go To 4

No

- Go To 8

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

- Replace the 1/1 O2 Sensor.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 5

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 Hg of the Vacuum Gauge reading?

Yes

- Go To 6

No

- Replace the MAP Sensor.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

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° 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)?

Yes

- Go To 7

No

- Replace the Engine Coolant Temperature Sensor.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

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

- Repair as necessary.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 11

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 between 4.1 and 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 between 4.1 and 5.0 volts to 2.5 volts with the jumper wire in place.

Did the O2 Sensor voltage change from between 4.1 and 5.0 volts to 2.5 volts with the jumper wire installed?

Yes

- Replace the O2 Sensor.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 9

NOTE: Remove the jumper wire before continuing.

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 between 4.1 and 5.0 volts?

Yes

- Go To 10

No

- Check the (K41) O2 Sensor 1/1 Signal 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.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

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

- Go To 11

No

- Check the O2 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.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

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

- Repair as necessary.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Replace and program the Powertrain Control Module.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

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

- Repair or replace fuel supply line as necessary.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 13

CAUTION: Stop All Actuations.

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

- Replace the Fuel Pump Inlet Strainer.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 14

14. FUEL PUMP MODULE

If there are no possible causes remaining, view repair.

Repair

- Replace the Fuel Pump Module.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test