EI08145 - 1.6L L91, P0420 Catalyst System Low Efficiency, O2 Lean Limit, Code P0131, P0133 (Engineering Information)

Some customers may comment that the Service Engine Soon (SES) light is illuminated.

Upon investigation, the technician may find DTC P0420 stored, possibly accompanied by an O2 lean limit code of P0131 or P0133.

GM Engineering is attempting to determine the cause of DTC P0420 setting. General Motors has a need to obtain technical information from the technician during diagnosis and after the repair is made.

Technicians are to follow the instructions below and e-mail the required snapshot information to Randy Risley at randy.risley@gm.com.

1. Follow P0420 diagnostics and repairs per SI. If SI diagnostics leads to a catalytic converter replacement conclusion, proceed to Step 2.

Important: DO NOT replace the catalytic converter.

2. Disconnect the battery for two minutes . The battery disconnect will reset the ECM NVM (non-volatile memory), causing a default run cycle of the catalyst monitor event. The ECM will run the event up to six consecutive times during the test drive as described in Step 6 below. The ECM will repeat the six consecutive run events once more after the key has been cycled off and back on.
3. Connect a Tech 2® and clear all DTCs.
4. Plan to test drive the vehicle for approximately twenty minutes to capture the catalyst monitoring event by following the Tech 2® driving instructions below.

Important: Refer to Corporate Bulletin Number 07-07-30-010 for information on the process of taking, uploading and e-mailing snap shots via TIS2WEB.

5. Prepare the Tech 2® for a test drive Snap Shot. With the vehicle running at idle in park, set the Tech 2® for:

•	Manual Trigger

•	Center Snapshot

•	Select Engine Data for Air Fuel Ratio, Front O2 Sensor, Rear O2 Sensor and Engine Run Time

6. Test drive the vehicle under light to moderate throttle to meet the following enable criteria:

•	Exceed ten minutes engine run time as shown on the Tech 2®.

•	Exceed 30 mph (48 km/h) for at least fifteen consecutive seconds.

•	Stop the vehicle and remain in drive position (neutral for manual transmission).

Important: The catalyst monitor event will occur during the sixty second stop as described in the next step.

•	Monitor the Tech 2®. The air fuel ratio will exceed 14.7:1 to approximately 16.2:1 and then drop below 14.7:1 to approximately 13.4:1 and then stabilize at 14.7:1. Capture this event by starting the snap shot with the manual trigger (center trigger).

Important: If the air-fuel ratio does not stray from 14.7:1 as described above, the ECM had not run the test. Do not trigger the snapshot. Return to Step 5.

•	DO NOT shut off the engine. Continue to test drive the vehicle in an effort to capture one more catalyst test events on the same snap shot.

•	Exceed 30 mph (48 km/h) for at least fifteen consecutive seconds during the drive.

•	Stop the vehicle and remain in drive position (neutral for manual transmission).

Important: The catalyst monitor event will occur during the sixty second stop as described in the next step.

•	Monitor the Tech 2® The air-fuel ratio will exceed 14.7:1 to approximately 16.2:1 and then drop below 14.7:1 to approximately 13.4:1 and then stabilize at 14.7:1. This event should be captured before the snap shot times out.

Important: One event capture per snap shot is required for this investigation. The second event capture is preferred but not required if the snap shot times out.

Important: Refer to Corporate Bulletin Number 07-07-30-010 for information on the process of taking, uploading and e-mailing snap shots via TIS2WEB.

7. Return to your service facility and e-mail the snap shot results to randy.risley@gm.com using TIS to Web snapshot e-mail. In your e-mail be sure to include the R.O. number, technician name and phone number.

Important: 

•	It is very critical to label the fuel injectors correctly.

•	Carefully package the original injectors in the replacement injector boxes and mark the last 8-digits of the VIN on the box. A parts return request will be faxed to your parts department.

8. Replace all four fuel injectors. Label the original fuel injectors with a paint pen to identify their corresponding cylinder replacement and vaildate the repair.

Important: You will NOT hear back from GM Engineering. E-mailing the snap shots is for data collection purposes ONLY. Continue to repair the vehicle as outlined below.

After replacing all four fuel injectors, perform the following diagnostics:

1. Validate the repair by a test drive and snap shot.
2. Plan to test drive the vehicle for approximately twenty minutes to capture the catalyst monitoring event by following the Tech 2® and driving instructions below.

Important: Refer to Corporate Bulletin Number 07-07-30-010 for information on the process of taking, uploading and e-mailing snap shots via TIS2WEB.

3. Prepare the Tech 2® for a test drive snap shot with the vehicle running at idle in park:

•	Manual Trigger

•	Center Snapshot

•	Engine Data

•	Select Engine data for Air-Fuel Ratio, Front and Rear O2 Sensors and Engine Run time

4. Test drive the vehicle under light to moderate throttle to meet the following enable criteria:

•	Exceed ten minutes of engine run time as shown on the Tech 2®.

•	Exceed 30 mph (48 km/h) for at least fifteen consecutive seconds.

•	Stop the vehicle and remain in the drive position (neutral for manual transmissions) for approximately sixty seconds.

Important: The catalyst monitor event will occur during the sixty second stop as described below.

•	Monitor the Tech2 ®. The air-fuel ratio will exceed 14.7:1 to approximately 16.2:1 and then drop below 14.7:1 to approximately 13.4:1 and then stabilize at 14.7:1. Capture this event by starting the snap shot with the manual trigger (center trigger).

Important: If the air-fuel ratio does not stray from 14.7:1 as described above, the ECM has not run the test. Do not trigger the snap shot. Return to Step 4.

•	DO NOT shut off the engine. Continue to test drive the vehicle in an effort to capture one more catalyst test events on the same snap shot.

•	Exceed 30 mph (48 km/h) for at least fifteen consecutive seconds during the drive.

•	Stop vehicle and remain in the drive position (neutral for manual transmissions).

•	Monitor the Tech 2®. The air-fuel ratio will exceed 14.7:1 to approximately 16.2:1 and then drop below 14.7:1 to approximately 13.4:1 and then stabilize at 14.7:1. This event should be captured before the snap shot times out.

Important: One event capture per snap shot is required for this investigation. The second event capture is preferred but not required if snap shot times out.

Important: Refer to Corporate Bulletin Number 07-07-30-010 for information on the process of taking, uploading and e-mailing snap shots via TIS2WEB.

5. Return to your service facility and e-mail the snap shot results to randy.risley@gm.com using TIS to Web snapshot e-mail. In your e-mail, include the R.O. number, technician name and phone number.

Important: You will NOT hear back from GM Engineering. E-mailing the snap shots is for data collection purposes ONLY.

For vehicles repaired under warranty, use: