Code P2096 Post Catalyst Fuel Trim System Too Lean Bank 1

So my truck is throwing this code. Autozone said there isn't a bad sensor, only that the computer sensed that the fuel was too lean at some point. I checked the air box to make sure it is sealed up and not seeping air. He said their computer system would tell him it was a sensor. Their code scanner is different than anyone else's that I have seen. I used 2 different gas stations between Wed-Sun due to traveling last week.

Could it be that the sensor before the catalytic converter is bad and the sensor after is still functioning and detecting that the fuel isn't mixed correctly?

I pulled the negative on the battery and reset it. The light stayed off for about 2-3 full days and it came back on this morning.

Anyone?

It would seem to me that it would be an exhaust leak or yhe 02 sensor. Have changed your exhaust recently? Specifically your catalytic converter.

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Ram-engineer said:

It would seem to me that it would be an exhaust leak or yhe 02 sensor. Have changed your exhaust recently? Specifically your catalytic converter.

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It has a flowmaster on it. It was on it when I bought it. It looks like it was put on a while back. Not recent. The catalytic converters look new and don't look to have been tampered with. I will put a down stream O2 sensor in it this weekend and report back. Is bank 1 the drivers side?

Thanks.

Soapstreet said:

So my truck is throwing this code. Autozone said there isn't a bad sensor, only that the computer sensed that the fuel was too lean at some point. I checked the air box to make sure it is sealed up and not seeping air. He said their computer system would tell him it was a sensor. Their code scanner is different than anyone else's that I have seen. I used 2 different gas stations between Wed-Sun due to traveling last week.

Could it be that the sensor before the catalytic converter is bad and the sensor after is still functioning and detecting that the fuel isn't mixed correctly?

I pulled the negative on the battery and reset it. The light stayed off for about 2-3 full days and it came back on this morning.

Anyone?

Click to expand...

P2096-DOWNSTREAM FUEL TRIM SYSTEM 1 LEAN


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 Powertrain Control Module (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. See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Initial Inspection and Diagnostic Overview\PCM Pre-Diagnostic Troubleshooting Procedure.

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 CHECKING THE EXHAUST SYSTEM FOR LEAKS test procedure. See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics\Checking The Exhaust System For Leaks.
Were any problems found?

Yes

Go To 7
No

Go To 2
2. ACTIVE DTC
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 may result in possible serious or fatal injury.

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

Perform the INTERMITTENT CONDITION diagnostic procedure. See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Initial Inspection and Diagnostic Overview\PCM Intermittent Condition Test.
3. CHECK THE FUEL DELIVERY SYSTEM
Perform the CHECKING THE FUEL DELIVERY SYSTEM test procedure. See: Engine, Cooling and Exhaust\Engine\Fuel Pressure\Testing and Inspection.
Were any problems found?

Yes

Repair as necessary.
Perform the PCM VERIFICATION TEST. See: Verification Tests\Powertrain Verification Test.
No

Go To 4
4. CHECKING THE OXYGEN SENSOR OPERATION
Perform the CHECKING THE OXYGEN SENSOR OPERATION test procedure. See: Powertrain Management\Computers and Control Systems\Testing and Inspection\Component Tests and General Diagnostics\Checking The Oxygen Sensor Operation.
Were any problems found?

Yes

Repair as necessary.
Perform the PCM VERIFICATION TEST. See: Verification Tests\Powertrain Verification Test.
No

Go To 5
5. CHECK THE ENGINE MECHANICAL SYSTEM
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 the PCM VERIFICATION TEST. See: Verification Tests\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.
Perform any technical service bulletins that may apply.
Were any problems found?

Yes

Repair as necessary.
Perform the PCM VERIFICATION TEST. See: Verification Tests\Powertrain Verification Test.
No

Replace and program the PCM.
Perform the PCM VERIFICATION TEST. See: Verification Tests\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 at a steady 80 kph (50 mph) to 97 kph (60 mph) for at least 10 minutes.
Stop the vehicle and turn the ignition off for 5 seconds.
Test drive the vehicle again at a steady 80 kph (50 mph) to 97 kph (60 mph) for at least 10 minutes.
Stop the vehicle.
With the scan tool, select View DTCs.
Does this DTC reset as a pending or active DTC?

Yes

Retest. Go To 1
No

Test Complete.
Perform the PCM VERIFICATION TEST. See: Verification Tests\Powertrain Verification Test.

Thank you for the information. Pardon my ignorance but I am unsure as to how I can use this.

Soapstreet said:

Thank you for the information. Pardon my ignorance but I am unsure as to how I can use this.

Click to expand...

This is basically everything a dealer or any legitimate mechanic shop would use to diagnose your problem. The top tells you what it takes to make that light come on. The rest are tests that need to be ran using a two way scan tool.

The most probable cause in your situation would be an exhaust leak somewhere between the exhaust manifold and the upstream (forward most) O2 sensor on the driver's side.

You can easily check that with fairly certain accuracy by using compressed air, a few rags, and a solution of water and dish soap in a squeeze bottle. With a cold engine and a helper, form a seal around the affected exhaust tailpipe with a rag or whatever you have and compressed air nozzle. (if you have duals and a Y pipe, plug the other side off) Squeeze some of the dishsoap/water solution starting with the exhaust manifold where it seals to the head while while flowing low pressure compressed air (less than 5 psi needed) into the tailpipe. If it bubbles, there's your leak. If it doesn't, keep moving aft to all exhaust joints and connections until bubbles are found.

This is very simple, almost free and is effectively the same thing a dealer will likely do with the exception of a fancy cone shaped tool to create the seal on the tailpipe. Hopefully this works, because it is the only thing you can do without having a two way [read: $$ expensive] scanner. Good luck to you and let us know what you find.

Rampant said:

This is basically everything a dealer or any legitimate mechanic shop would use to diagnose your problem. The top tells you what it takes to make that light come on. The rest are tests that need to be ran using a two way scan tool.

The most probable cause in your situation would be an exhaust leak somewhere between the exhaust manifold and the upstream (forward most) O2 sensor on the driver's side.

You can easily check that with fairly certain accuracy by using compressed air, a few rags, and a solution of water and dish soap in a squeeze bottle. With a cold engine and a helper, form a seal around the affected exhaust tailpipe with a rag or whatever you have and compressed air nozzle. (if you have duals and a Y pipe, plug the other side off) Squeeze some of the dishsoap/water solution starting with the exhaust manifold where it seals to the head while while flowing low pressure compressed air (less than 5 psi needed) into the tailpipe. If it bubbles, there's your leak. If it doesn't, keep moving aft to all exhaust joints and connections until bubbles are found.

This is very simple, almost free and is effectively the same thing a dealer will likely do with the exception of a fancy cone shaped tool to create the seal on the tailpipe. Hopefully this works, because it is the only thing you can do without having a two way [read: $$ expensive] scanner. Good luck to you and let us know what you find.

Click to expand...

Wow. You are the man. Thanks!

Soapstreet said:

Wow. You are the man. Thanks!

Click to expand...

No problem. If you don't have access to compressed air, you can be creative. It's really not pressure you need, it's flow. For example, you could use a leaf blower idling and taped to the tailpipe with a flex hose, a hair dryer, etc., anything that moves air and can be captured. Just not too much.