GPEC

P2096-DOWNSTREAM FUEL TRIM SYSTEM 1 LEAN

For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
With the engine running in closed loop, the ambient/battery temperature above -7° C (20° F) and altitude below 8500 ft.

- Set Condition:
The conditions that cause this diagnostic to fail is when the upstream O2 sensor becomes biased from an exhaust leak, O2 sensor contamination, or some other extreme operating condition. The downstream O2 sensor is considered to be protected from extreme environments by the catalyst. The PCM monitors the downstream O2 sensor feedback control, called downstream fuel trim, to detect any shift in the upstream O2 sensor target voltage from nominal target voltage. The value of the downstream fuel trim is compared with the lean thresholds. Every time the value exceeds the calibrated threshold, a fail timer is incremented and mass flow through the exhaust is accumulated. If the fail timer and accumulated mass flow exceed the fail thresholds, the test fails and the diagnostic stops running for that trip. If the test fails on consecutive trips, a DTC is set.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

Diagnostic Test

1. EXHAUST LEAK

NOTE: A thorough exhaust leak test must be completed before removing an O2 Sensor or any other part from the exhaust system. Do not remove any parts before an exhaust leak check has been completed.

NOTE: An exhaust leak may cause downstream fuel adaptives to rail out, resulting in a false O2 Sensor failure

Perform the diagnostic procedure for *CHECKING THE EXHAUST SYSTEM FOR LEAKS. Checking the Exhaust System For Leaks

Were any problems found?

Yes

- Go to 7

No

- Go to 2

2. DTC IS ACTIVE
Diagnose and repair any other active component or circuit DTCs before continuing with this procedure.
Turn the ignition on.
With the scan tool, select View DTCs. Copy DTC and Freeze Frame information.
Start the engine and allow it to reach operating temperature.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

NOTE: Attempt to operate the vehicle under conditions similar to which the DTC was set.

NOTE: It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.

With a scan tool, select View DTCs.
Is the status Active for this DTC?

Yes

- Go to 3

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.Checking For An Intermittent DTC

3. CHECKING THE FUEL DELIVERY SYSTEM
Perform the diagnostic procedure for *CHECKING THE FUEL DELIVERY SYSTEM. Checking the Fuel Delivery System
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 4

4. CHECKING THE OXYGEN SENSOR OPERATION
Perform the diagnostic procedure for *CHECKING THE OXYGEN SENSOR OPERATION. Checking the Oxygen Sensor Operation
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 5

5. CHECKING THE ENGINE MECHANICAL SYSTEM
Perform the diagnostic procedure for *CHECKING THE ENGINE MECHANICAL SYSTEM. Checking the Engine Mechanical System

Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Go to 6

6. POWERTRAIN CONTROL MODULE (PCM)
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors relative to the components tested in this procedure.
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Monitor the scan tool data relative to the components tested in this procedure and wiggle test the wiring and connectors.
Look for the data to change or for a DTC to set during the wiggle test.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test.Powertrain Verification Test

No

- Replace and program the PCM.
- Perform the PCM Verification Test.Powertrain Verification Test

7. EXHAUST LEAK
Repair the exhaust leak(s) as necessary.
Start the engine and allow it to reach operating temperature.
Test drive the vehicle for at least 5 minutes.
During the test drive, accelerate from 64 kph (40 mph) to 80 kph (50 mph), then release the accelerator pedal for at least 3 seconds. Repeat this procedure a minimum of 10 times.
Stop the vehicle and turn the ignition off for 5 seconds.
Test drive the vehicle again for at least 5 minutes.
During the test drive, accelerate from 64 kph (40 mph) to 80 kph (50 mph), then release the accelerator pedal for at least 3 seconds. Repeat this procedure a minimum of 10 times.
Stop the vehicle.
With the scan tool, select View DTCs.
Does this DTC reset as a pending or stored DTC?

Yes

- Retest. Go to 1

No

- Test Complete.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.