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Code P0496 04 Avalanche

RickCos

By RickCos
in Ask A GM Technician

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RickCos Enthusiast

RickCos

Posted
Posted

My CEL went on and I had the code read (P0496)and reset. My mechanic checked the evap lines to make sure they were Ok and I replaced the gas cap. I don't want to just throw parts at the problem.

 

Both times the light came on occured during starting. it started right up but it was for lack of a better word, a violent start. It kicked over hard. Another sympton is right after top off the gas tank, the engine just spins and does not start. On the second try it kicks right over. Lastly, I was idling in a driveway on a steep grade and the engine started losing rpms and almost shut down but didn't.

 

A poster on another board has the same issue and symptoms. He had the solenoid replaced on the evap canister but after 2 weeks the CEL came back on.

 

Any input to track down this problem.

 

Thanks!!

ryank1 Enthusiast

ryank1

Posted
Posted

Hope this helps

DTC P0496

System Description

This DTC tests for undesired intake manifold vacuum flow to the evaporative emission (EVAP) system. The control module seals the EVAP system by commanding the EVAP canister purge solenoid valve Closed and the EVAP canister vent solenoid valve Closed. The control module monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is more than a predetermined value within a predetermined time, 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 solenoid valves.

 

Control Module Command

EVAP Canister Purge Solenoid Valve

EVAP Canister Vent Solenoid Valve

 

ON

Open

Closed

 

OFF

Closed

Open

 

 

Conditions for Running the DTC

DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0156, P0157, P0158, P0160, P0161, P0220, P0442, P0443, P0449, P0452, P0453, P0455, P0502, P0503, P1111, P1112, P1114, P1115, P1121, P1122, P1125, P2135 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 4-30°C (39-86°F).

The intake air temperature (IAT) is between 4-30°C (39-86°F).

The start up ECT and IAT are within 9°C (16°F) of each other.

Conditions for Setting the DTC

A continuous open purge flow condition is detected during the diagnostic test.

The fuel tank pressure decreases to less than -11 inches H2O.

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 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.

 

Step

Action

Values

Yes

No

 

Schematic Reference: Emission Hose Routing Diagram

 

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

 

2

Start the engine.

Seal the evaporative emission (EVAP) system using the Purge/Seal function with a scan tool.

Increase the engine idle to 1,200-1,500 RPM.

Observe the fuel tank pressure sensor in H2O with a scan tool.

Is the fuel tank pressure sensor parameter within the specified value?

-1 to +1 in H2O

Go to Intermittent Conditions

Go to Step 3

 

3

Turn OFF the ignition.

Disconnect the EVAP purge pipe from the EVAP purge solenoid valve.

Turn ON the ignition, with the engine OFF.

Observe the fuel tank pressure sensor in H2O with a scan tool.

Is the fuel tank pressure sensor parameter within the specified range?

-1 to +1 in H2O

Go to Step 4

Go to Step 5

 

4

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

 

Did you complete the replacement?

--

Go to Step 6

--

 

5

Replace the fuel tank pressure (FTP) sensor. Refer to Fuel Tank Pressure Sensor Replacement .

 

Did you complete the replacement?

--

Go to Step 6

--

 

6

Connect all EVAP hardware that was previously disconnected.

Seal the EVAP system using the Purge/Seal function with a scan tool.

Start the engine and idle at 1,200-1,500 RPM.

Observe the fuel tank pressure sensor parameter with a scan tool.

Is the fuel tank pressure sensor parameter within the specified range?

-1 to +1 in H2O

Go to Step 7

Go to Step 2

 

7

Observe the Capture Info with a scan tool.

 

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK

 

 

 

--------------------------------------------------------------------------------

Document ID# 1251054

2004 Chevrolet Avalanche - 4WD

RickCos Enthusiast

RickCos

Posted
  • Author
Posted

Thanks for the response Ryan but I do not have the capability to perform those tests. What I did do was order the the vent valve and solenoid from AC Delco and will install them myself. My mechanic checked the lines for leaks but did not see anything.

 

The "tighten the gas cap" light came on this morning. This is 3 weeks after i replaced the factory cap with a stant cap thinking this could have led to the P0496 code.

 

Any input on the gas cap issue?

 

Thanks

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