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how do i fix error code p0449 on my 2005 chevy tahoe

Resolved Question:

how do i fix error code p0449 on my 2005 chevy tahoe
Submitted: 8 years ago.
Category: Chevy
Expert:  Tim's Auto Repair replied 8 years ago.
this may help you

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Diagnostic Chart (Part 1 Of 3)   

Diagnostic Chart (Part 2 Of 3)   

Diagnostic Chart (Part 3 Of 3)   

A voltage is supplied directly to the Evaporative Emission (EVAP) vent valve solenoid. The Powertrain Control Module (PCM) controls the solenoid by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. Each driver has a fault line which the PCM monitors. The voltage of the control circuit should be low, near 0 volts , when the PCM commands a component ON. The voltage potential of the circuit should be high, near the battery voltage, when the PCM commands the control circuit to a component OFF. If the fault detection circuit senses a voltage other than what the PCM expects, the fault line status changes causing the DTC to set.


•The engine speed is more than 400 RPM .
•The ignition voltage is between 6-18 volts .

•The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
•The conditions are present for a minimum of 5 seconds .

•The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
•The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

•The PCM turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
•A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
•A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
•Use a scan tool in order to clear the MIL and the DTC.

IMPORTANT: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

Using Freeze Frame and Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid in determining how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that you observed. This will isolate when the DTC failed.

For an intermittent, refer to Symptoms. See: Symptom Related Diagnostic Procedures

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

2.Listen for an audible click when the solenoid operates. Be sure that both the ON and the OFF states are commanded. Repeat the commands as necessary.
3.This test can detect a partially shorted coil which would cause excessive current flow. Leaving the circuit energized for 2 minutes allows the coil to warm up. When warm the coil may open (amps drop to 0) or short (goes above 0.75 amp ).
7.Momentarily probe the solenoid control circuit to ground. Listen for an audible click when the solenoid operates.
18.If no trouble is found in the control circuit or the connection at the PCM, the PCM may be faulty, however, this is an extremely unlikely failure.
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