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Old 05-16-2007, 04:36 PM   #1
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Default 2 CEL Codes

Hi there,

I am doing some "homework" for a friends car:

-2001 V6 3.8L Bonneville SE
-115,000 miles

I pulled the codes off his car and got:

P0420 - Catalyst Efficiency Below Threshold (Bank 1)
P0440 - EVAP Emission Control System Malfunction

I am not well versed with this vehicles platform and am hoping I can get some advice based upon similar experiences

Thanks,

Brian
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Old 05-16-2007, 07:22 PM   #2
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P0440 can be anything from a loose gas cap to solenoid failures. Start by making sure the gas cap is always put on tightly (at least 3 clicks). If so, then try cleaning up the top of the filler tube for the gas tank, and the gas cap seal. Put a little silicone grease on it to keep it from rusting again.

Failing that, check all of the evap. fittings. Start with the purge solenoid under the hood. It'* roughly cylindrical in shape and I think sits toward the front side of the engine on the n/a engines. Then the canister, under the car roughly under the back seat, and then the vent valve by the back wheel. The one that I tracked down was corrected by removing, cleaning and lubing up the vent valve. Here'* how to remove that.
EVAPORATIVE EMISSION (EVAP) CANISTER VENT VALVE REPLACEMENT

This the information for setting and testing for P0420. That must have been set first, as that indicates that code P0420 will not be set if P0440 is present. Let'* fix the p0440 first, and see what happens from there.
P0420
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Old 05-21-2007, 10:43 AM   #3
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Archon'* advice is spot on for the P0440. I got this code and tightened the gas cap. Didn't go away. Put a new gas cap on, didn't go away. I finally looked into it and rolled some dice. I found that I could buy a purge control solenoid, vent solenoid and Fuel Pressure Sensor for about $70. I checked the canister under the rear driver side door, and it had no fuel in it. Bought all three parts, spend 20 minutes putting them in (and I am a slow worker), and code gone. I know- not the preferred way to fix things, but if you don't want to spend a lot of time diagnosing, this may be a route for you to take. Your money, your call.

As for the other code- sounds like an o2 sensor or cat problem. Check and make sure your ignition wires in the back of the engine are not hitting the o2 sensor. I'm sure someone on here will know more than I do about it.
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Old 05-22-2007, 02:16 AM   #4
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P0420 is being set because the post-cat (downstream) O2 sensor is changing to rapidly in response to the switching being done by the pre-cat (upstream) O2 sensor signal and the CEL will be turned on if it fails subsequent tests run by the PCM. In essence what is happening is that the cat(*) actually store oxygen to help in the coversion of exhaust from Hydrocarbons, Carbon Monoxide, and NOx into water vapor, carbon dioxide, and nitrogen when working properly. In this case the switching by the post-cat O2 would be slow compared to the pre-cat O2. I'd say, 8 - 9 times out of 10 it was just a bad O2 sensor, especially if any exhaust work had been done recently where the post-cat O2 sensor had been removed (perhaps dropped) or was subject to a high level of heat, say from a torch/welder, welding nearby. A/C delco O2 sensors can be very fragile.

Here is GM'* write up on it;
Quote:
DTC P0420
Circuit Description
To control emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx), a 3-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, converting the HC and CO into harmless water vapor and carbon dioxide. The catalyst also reduces NOx by converting the NOx to nitrogen. The converter also has the ability to store excess oxygen and release the stored oxygen to promote these reactions. This oxygen storage capacity (OSC) is a measurement of the catalysts ability to control emissions. The powertrain control module (PCM) monitors this process using a heated oxygen sensor (HO2S) located in the exhaust stream past the 3-way converter. When the catalyst is functioning properly, the HO2S 2 is slow to respond to a large change in the HO2S 1 signal. When the HO2S 2 responds quickly to a large change in the HO2S 1 signal, the OSC and efficiency of the catalyst are considered to be degraded and the MIL will be illuminated if subsequent tests also indicate a failure.

Conditions for Running the DTC
1) Meet conditions for engine warm up. Use the scan tool catalyst data list in order to verify the following.
- DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0171, P0172, P0201-206, P0300, P0336, P0341, P0401, P0403, P0404, P0405, P0410, P0412, P0418, P0440, P0442, P0443, P0446, P0449, P0502, P0503, P0506, P0507, P1133, P1134, P1336, P1351, P1352, P1361, P1374, or P1441 are not set.
- The engine has been running more than 10 minutes.
- The engine coolant temperature (ECT) is 70C-124C (158F-255F).
- The barometer (BARO) is above 75 kPa (10.8 psi).
- The vehicle is in closed loop.
- The intake air temperature (IAT) is above -20C to 100C (-4F to 212F).
- The battery voltage is above 10.7 volts
2) Warm up the catalyst.
- Fully open the hood.
- Set the transmission is in park (automatic) or in neutral (manual).
- Set the parking brake.
- Press and hold the service brake.
- Each time the engine is started the diagnostic can run up to 18 times. After the 10-minute run time and before the diagnostic runs the first time, the engine must run an additional 5 minutes between 1500-2500 RPM. Any additional tests on the same key cycle, the engine speed must be between 1500-2500 RPM for 1 minute.
In order to activate the diagnostic, return the engine to idle and put the vehicle in drive, or depress the clutch for a manual transmission.
3) Test the catalyst.
- Transmission is in drive (automatic) or in neutral (for manuals with clutch depress).
- VIN K California Emissions-- Within 60 seconds the air fuel ratio will go rich below 14.1 for up to 6 seconds. Then the air-fuel ratio may go lean above 15.3 for up to 8 seconds.
- VIN K FED Emissions--Within 60 seconds the air fuel ratio will go lean above 15.3 for up to 6 seconds, then may go rich below 14.1 for up to 7 seconds.
- VIN 1 -- Within 60 seconds, the air fuel ratio will go rich below 14.1 for up to 7 seconds. Then the air-fuel ratio may go lean above 15.3 for up to 9 seconds.
- Use the scan tool in order to check if DTC P0420 has passed or failed this key cycle.

Conditions for Setting the DTC
The PCM determines that the catalysts oxygen storage capacity is below an acceptable threshold.

Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

Conditions for Clearing the MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
Check for the following conditions:

The PCM will not enable the catalyst test until the following conditions are met:
- The engine idle speed is within 100 RPM of the desired idle.
- The throttle position (TP) is 1 percent or less.
- The short term integrator is between -20 percent and +20 percent .
The catalyst test will abort if the vehicle conditions fall outside the conditions listed below while the test is running:
- The engine idle speed is within 125 RPM of the desired idle.
- The throttle position (TP) is 1 percent or less.
- The short term integrator is between -20 percent and +20 percent .

Important
When using the scan tool to force the cooling fans on, use the Next List and the Previous List soft keys in order to enter the catalyst data list. If the catalyst data list is not entered this way, the cooling fan control will be canceled.


The catalyst test may abort due to a change in engine load (i.e., A/C, coolant fan). If this problem occurs, use the scan tool in order to force the cooling fans on, then return to step 2 in the table.
- The number of attempted tests is limited to 18 per key cycle.
- More than 6 tests may have to be attempted in order to get 6 completed tests. An aborted test counts as an attempted test.
- If 18 tests have been attempted, and a decision has not been made this key cycle, turn the key OFF for 30 seconds. Start the vehicle and perform the Conditions for Running the DTC, including the 10 minute engine run time.
- After returning to an idle the HO2S 1 signal may stay rich or lean for several seconds, causing the test to be delayed.
- Inspect the PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly-formed or damaged terminals, and faulty terminal-to-wire connections. Use a corresponding mating terminal in order to test for proper terminal tension.
- Inspect the wiring harness for damage. If the harness appears to be OK, observe the display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.

Test Description
The numbers below refer to the step numbers on the diagnostic table.

1) The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and to store the Freeze Frame/Failure Records data on the scan tool if applicable.

2) If any component DTCs are set, diagnose those DTCs first. A fault in a component can cause the converter to appear degraded or may cause converter failure.

3) Clearing the DTCs allows the catalyst test to be run up to 18 times and completed up to 6 times this ignition cycle. If the A/C is not turned off the diagnostic may not run. The engine must be warm. The converter needs to be warmed by raising the engine speed above idle for the specified time prior to each attempted test. Check if the DTC passed or failed this ignition cycle. If the DTC does not pass or fail look, for a possible reason that would cause the test to abort.

4) This step includes checks for conditions that can cause the 3-way converter to appear degraded. Repair any problems found before proceeding with this table.

5) If the 3-way converter needs to be replaced, ensure another condition is not present which could damage the converter. Such conditions may include misfire, leaking or plugged fuel injectors, high engine oil or coolant consumption, retarded spark timing, or weak spark. Correct any possible cause of converter damage before replacing the converter.


Step 1
Did you perform the Diagnostic System Check-Engine Controls?
Yes: Go to Step 2
No: Go to Diagnostic System Check - Engine Controls

Step 2
If any DTCs are stored, save the Freeze Frame and Fail Records information using the scan tool.

Are any other DTCs set?
Yes: Go to Diagnostic Trouble Code (DTC) List
No: Go to Step 3

Step 3

Important
If the A/C is left on the diagnostic may not run.

1) Turn the A/C OFF.
2) Clear the DTCs.
3) Start the engine and wait until the vehicle is fully warmed up for at least 10 minutes.
4) Run the engine above 1500 RPM for an additional 5 minutes. (One minute for each additional attempt at 1500 RPM on the same key cycle). The vehicle may be driven for the 5 minute run time.
5) Fully open the hood.
6) Operate the vehicle within the Conditions for Running the DTC.

Important
If more than 6 tests have been attempted and the DTC has not passed or failed this ignition cycle the test may be aborted. Refer to Diagnostic Aids.

7) The test may need to be completed up to 6 times in order to pass or fail.

Does the scan tool indicate the DTC ran and passed this ignition cycle?
Yes: System OK
No: Go to Step 4

Step 4
1) Visually and physically inspect the 3-way catalytic converter for damage.
2) Check for the following:
- Dents
- Severe discoloration caused by excessive temperatures
- Holes
- Internal rattles caused by damaged catalyst substrate
3) Also, ensure that the 3-way catalytic converter is the correct original equipment part.

Did your inspection reveal a problem?
Yes: Go to Step 9
No: Go to Step 5

Step 5
1) Visually and physically inspect the exhaust system for leaks, restrictions, or damage.
2) If a problem is found, repair as necessary.

Did your inspection reveal a problem?
Yes: Go to Step 7
No: Go to Step 6

Step 6
Visually check for the following:

- Damaged oxygen sensors
- Damage to the HO2S wiring harness

Was a problem found?
Yes: Go to Step 8
No: Go to Step 9

Step 7
Repair the exhaust system as necessary. Refer to Restricted Exhaust in Engine Exhaust.

Did you complete the repair?
Yes: Go to Step 10
--

Step 8
Repair the HO2S sensor and wiring as necessary. Refer to Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems.

Did you complete the repair?
Yes: Go to Step 10
--

Step 9

Notice
In order to avoid damaging the replacement three-way catalytic converter, correct the engine misfire or mechanical fault before replacing the three-way catalytic converter.

Replace the 3-way catalytic converter. Refer to Exhaust System Replacement in Engine Exhaust.

Did you complete the repair?
Yes: Go to Step 10
--

Step 10
1) Clear the DTCs using the scan tool.

Important
If the A/C is left on, the following diagnostic may not run.

2) Turn OFF the A/C.
3) Start the engine and wait until the vehicle is fully warmed up for at least 10 minutes.
4) Run the engine above 1500 RPM for an additional 5 minutes. (One minute for each additional attempt at 1500 RPM on same key cycle). The vehicle may be driven for the 5 minute run time.
5) Fully open the hood.
6) Operate the vehicle within the Conditions for Running the DTC.

important
If more than 6 tests have been attempted and the DTC has not passed or failed this ignition cycle, the test may be aborted. Refer to Diagnostic Aids.

7) The test may need to be completed up to 6 times in order to pass or fail.

Does the scan tool indicate the DTC ran and passed this ignition cycle?
Yes: Go to Step 11
No: Go to Step 4

Step 11
Are any additional DTCs set that have not been diagnosed?
Yes: Go to Diagnostic Trouble Code (DTC) List
No: System OK
As for P0440, as mentioned, it can be either a purge solenoid which in some cases can be easily identified as the purge solenoid can be VERY noisy in the process, and/or a gas cap issue. P0440 is set when the EVAP system'* vacuum level is breached due to a leak by monitoring pressure in the tank. If it is simply a gas cap issue, the PCM will clear the code itself after three consecutive, successful operating cycles. The reason it clears so quickly is because it generally really isn't an issue. Anyway, the code itself is set when the PCM runs a diagnostic test on it and the system is not able to meet the threshold minimum vacuum level. But just don't go replacing parts because a couple people here tell you that'* the problem. If I had a nickel every time a customer came in swearing up and down a problem was caused by part A when after troubleshooting, it was part W.

Here is GM'* write up on it;

Quote:
DTC P0440
System Description
The control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge valve OPEN and the EVAP vent valve CLOSED . This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves.

Control Module Command
EVAP Canister Purge Valve
EVAP Canister Vent Valve

ON
Open
Closed

OFF
Closed
Open


Conditions for Running the DTC
- DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121, or P1122 are not set.
- The ignition voltage is between 10-18 volts.
- The barometric pressure (BARO) is more than 75 kPa.
- The fuel level is between 15-85 percent.
- The engine coolant temperature (ECT) is between 4-30C (39-86F).
- The intake air temperature (IAT) is between 4-30C (39-86F).
- The start-up ECT and IAT are within 9C (16F) of each other.
- The vehicle speed sensor (VSS) is less than 121 km/h (75 mph).

Conditions For Setting the DTC
The EVAP system is not able to achieve or maintain vacuum during the diagnostic test.

Action Taken When the DTC Sets
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. - The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
- The control module will turn the malfunction indicator lamp (MIL) OFF during the first consecutive trip in which the diagnostic has been run and passed.
- A current DTC, Last Test Failed, clears when the control module turns OFF the MIL.
- The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure.
- Use the scan tool in order to clear the DTC.

Diagnostic Aids
- Use the J 41413 EVAP Pressure and Purge Station in order to pressurize the EVAP system to aid in locating intermittent leaks. Move all EVAP components while testing with the J 41416 Ultrasonic Leak Detector.
- A temporary blockage in the EVAP canister purge valve, purge pipe or EVAP canister could cause an intermittent condition. To repair a blockage in the EVAP system, refer to Evaporative Emission (EVAP) System Cleaning .
- Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description
The numbers below refer to the step numbers on the diagnostic table.

4) This step is used to verify if a leak is present.

5) This step verifies proper operation of the FTP sensor.

This step tests the EVAP canister purge valve for a restriction or blockage.


Step 1
Did you perform the Diagnostic System Check-Engine Controls?
--
Yes: Go to Step 2
No: Go to Diagnostic System Check - Engine Controls

Step 2
Does the scan tool indicate DTC P0443 or DTC P0449 are also set?
--
Yes: Go to Diagnostic Trouble Code (DTC) List
No: Go to Step 3

Step 3
1) Inspect the EVAP system for the following conditions:
- Loose, missing, or damaged service port schrader valve
- Loose, incorrect, missing, or damaged fuel fill cap
- A damaged EVAP canister purge valve
2) Raise the vehicle on a hoist. Refer to Lifting and Jacking the Vehicle in General Information.
3) Inspect the EVAP system for the following conditions:
- Disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses
- A damaged EVAP canister vent valve or EVAP canister

Did you find and correct the condition?
--
Yes: Go to Step 18
No: Go to Step 4

Step 4

Important
Always zero the EVAP pressure and vacuum (in H2O) gages on the EVAP pressure and purge station before proceeding with diagnosis.


1) Install the J 41415-40 Fuel Tank Cap Adapter.
2) Connect the J 41413 EVAP Pressure and Purge Station and the vehicle fuel fill cap to the J 41415-40 .
3) Turn ON the ignition, with the engine OFF.
4) With the scan tool, seal the EVAP system.
5) With the J 41413 pressurize the system to the specified value.
6) Rotate the J 41413 rotary switch to the OFF/HOLD position. Monitor the pressure gage for 1 minute.

Did you obtain and hold the specified value?
Specified Value = 5" in H2O

Yes: Go to Step 5
No: Go to Step 7

Step 5
Compare the EVAP pressure and purge station value to the scan tool FTP sensor value.

Does EVAP pressure and purge station value measure near the scan tool value?
--
Yes: Go to Step 6
No: Go to Step 11

Step 6
1) Monitor the pressure gage on the J 41413 .
2) Disconnect the EVAP purge pipe from the EVAP purge valve.

Does the EVAP system pressure decrease?
--
Yes: Go to Step 8
No: Go to Step 9

Step 7
1) With the J 41413 , continuously pressurize the EVAP system.

Important
The fuel tank may need to be partially lowered to inspect components located in the upper portion of the tank.

2) With the J 41416 Ultrasonic Leak Detector inspect for leaks in the following locations:
- The EVAP system purge pipe Refer to Evaporative Emission (EVAP) Hoses/Pipes Replacement - Engine/Chassis .
- The EVAP vapor pipe Refer to Evaporative Emission (EVAP) Hoses/Pipes Replacement - Canister/Fuel Tank .
- The EVAP vent hose/pipe Refer to Evaporative Emission (EVAP) Canister Vent Valve Replacement .
- The fuel fill pipe/hose and fuel fill cap Refer to Filler Tube Replacement .
- The EVAP canister Refer to Evaporative Emission (EVAP) Canister Replacement .
- The EVAP canister vent valve Refer to Evaporative Emission (EVAP) Canister Vent Valve Replacement .
- The EVAP canister purge valve Refer to Evaporative Emission (EVAP) Canister Purge Valve Replacement .
- The fuel sender assembly and/or seal Refer to Fuel Sender Assembly Replacement .
- The FTP sensor seal Refer to Fuel Tank Pressure Sensor Replacement .
- The fill limiter vent valve, pressure relief valve, rollover valve, or fuel tank Refer to Fuel Tank Replacement .

Did you find and correct the condition?
--
Yes: Go to Step 18
No: Go to Diagnostic Aids

Step 8
1) Attach a vacuum gage to the EVAP purge valve purge pipe port.
2) Start the engine and allow the engine to idle.
3) Command the EVAP purge valve to 50 percent with a scan tool.

Does the vacuum gage show vacuum more than the specified value?
Specified Value = 10" in H2O

Yes: Go to Intermittent Conditions
No: Go to Step 12

Step 9
1) Monitor the pressure gage on the J 41413 .
2) Disconnect the EVAP purge pipe from the EVAP canister.

Does the EVAP system pressure decrease?
--
Yes: Go to Step 14
No: Go to Step 10

Step 10
1) Monitor the pressure gage on the J 41413 .
2) Disconnect the EVAP purge pipe from the EVAP purge valve.

Does the EVAP system pressure decrease?
--
Yes: Go to Step 17
No: Go to Step 13

Step 11
Monitor the FTP sensor voltage with a scan tool.

Is the FTP sensor voltage more than the specified value?
Specified Value = 4.3 V

Yes: Go to DTC P0453
No: Go to Step 15

Step 12
Inspect the vacuum source to the EVAP purge valve for blockage, cuts, or disconnects. Repair as necessary.

Did you find and correct the condition?
--
Yes: Go to Step 18
No: Go to Step 16

Step 13
Repair the pinched or obstructed EVAP vapor pipe.

Did you complete the repair?
--
Yes: Go to Step 18
--

Step 14
Repair the restriction in the EVAP purge pipe. Refer to Evaporative Emission (EVAP) System Cleaning .

Did you complete the repair?
--
Yes: Go to Step 18
--

Step 15
Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement .

Did you complete the replacement?
--
Yes: Go to Step 18
--

Step 16
Replace the EVAP purge valve. Refer to Evaporative Emission (EVAP) Canister Purge Valve Replacement .

Did you complete the replacement?
--
Yes: Go to Step 18
--

Step 17
Replace the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement .

Did you complete the replacement?
--
Yes: Go to Step 18
--

Step 18
1) Turn ON the ignition, with the engine OFF.
2) Command the EVAP canister vent valve ON with a scan tool.

Important
DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.

3) Pressurize the EVAP system to the specified value with the J 41413 .
4) Place the control **** on the J 41413 to the OFF/HOLD position.
5) Monitor the EVAP system pressure on the J 41413 for 5 minutes.

Does the EVAP system pressure remain constant?
Specified Value = 5" in H2O

Yes: Go to Step 19
No: Go to Step 7

Step 19
1) Monitor the pressure gage on the J 41413 .
2) Command the EVAP purge valve to 50 percent with a scan tool.

Does the EVAP system pressure decrease?
--
Yes: Go to Step 20
No: Go to Step 9

Step 20
With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?
--
Yes: Go to Diagnostic Trouble Code (DTC) List
No: System OK
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