Mechanics

CHEVROLET SILVERADO SENSOR PROBLEM

2000 Chevrolet Silverado • 165,000 miles

Cars service engine soon light is on. Had codes read came up p0440-evap small leak/no flow condition, and p0459-evaporative emission purge solenoid control circuit high voltage. No problems when running, just fuel gauge fluctuating/ reading empty when in park. Slowly returns to accurate amount when driving. Any diagnosis/ fixes? (Tightened cap and pulled fuses/reset light.) Thanks
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Guest
March 22, 2013.



Re setting light does nothing as the issue has not been fixed.

440

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) tests the Evaporative Emission (EVAP) system for the following conditions: Large and small leaks
Excess vacuum
Purge flow during non-commanded conditions
Fuel level and fuel pressure sensor faults
EVAP purge and vent valve faults

The PCM monitors the fuel tank pressure sensor in order to determine the level of vacuum or pressure in the EVAP system. The PCM commands both the EVAP purge solenoid and the EVAP vent valve ON when the Conditions for Running the DTC are met in order to apply an engine vacuum to the EVAP system. The PCM commands the EVAP purge solenoid OFF once the system has reached a predetermined level of vacuum. This test confirms if a vacuum can be achieved in the EVAP system. Failure to develop a vacuum may be caused by a large leak or a restriction. This DTC sets after twice failing the above test.

CONDITIONS FOR RUNNING THE DTC

No active Manifold Absolute Pressure (MAP) DTCs
No active Intake Air Temperature (IAT) DTCs
No active Throttle Position (TP) DTCs
No active Heated Oxygen Sensor (HO2S) DTCs
No active Vehicle Speed Sensor (VSS) DTCs
No active system voltage DTCs
The ignition voltage is between 10 volts and 18 volts.
The barometric pressure is more than 75 kpa.
The fuel level is between 15 percent and 85 percent of full capacity.
The Engine Coolant Temperature (ECT) is between 4°C (39°F) and 30°C (86°F).
The Intake Air Temperature (IAT) is between 4°C (39°F) and 30°C (86°F).
The start up ECT and IAT are within 9°C (16°F) of each other.

CONDITIONS FOR SETTING THE DTC
The EVAP system cannot develop a vacuum more than a predetermined value.

IMPORTANT: This DTC does NOT report a first failed test. A first fail of this DTC will have a scan tool status as Not Run. Use the scan tool data display parameter of EVAP test result in order to determine if this DTC has failed or passed for this ignition cycle.

ACTION TAKEN WHEN THE DTC SETS

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.

CONDITIONS FOR CLEARING THE MIL/DTC

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.

DIAGNOSTIC AIDS

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.
An accurate indication of fuel level is required for the PCM to properly pass or fail this DTC. Always diagnose fuel level sensor DTCs before performing this DTCs diagnostic table. Always inspect for fuel level sensor DTCs stored as History.
The Service Bay Test may have to be performed in cold ambient air temperatures when the vehicle is running a winter grade fuel. The scan tool displays a message when the Service Bay Test does not run.
Inspect for charcoal release from the vapor canister. Refer to Evaporative Emission (EVAP) System Cleaning.

CONDITIONS FOR RUNNING THE SERVICE BAY TEST

The battery voltage is between 10.5 volts and 17.5 volts.
The fuel level is between 15 percent and 85 percent of the full capacity.
The engine temperature is between 3.5°C (38°F) and 35°C (95°F).

Perform a physical inspection of the EVAP system.
Inspect for the following conditions: A loose, missing, defective, or incorrect fuel tank cap
Incorrectly routed or defective EVAP system vacuum and vapor lines
A malfunctioning or damaged vapor canister
Charcoal release from the vapor canister-Refer to Evaporative Emission (EVAP) System Cleaning.

The vacuum and pressure in the EVAP system is measured in inches of water (H2O). Most gauges measure vacuum in inches of Mercury (Hg) and pressure in pounds Per Square Inch (psi). The following shows how the values compare: TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.

You may need to partially lower the fuel tank in order to inspect the upper portion of the tank and the EVAP line connections.
An intermittent leak or restriction is indicated if the vehicle passes the Service Bay Test. A fuel tank cap that is loose or off causes this DTC to set. If the Service Bay Test cannot be run, proceed to step 5. If a fault is not currently present, the diagnostic table steps will return you to step 3.

This step tests for a leak at the top of the fuel tank, at the fuel filler hose, and the fuel cap. Place the ultrasonic leak detector in these areas. Refer to the information supplied with the EVAP pressure and purge diagnostic cart on proper setup and adjustment procedures.
Tests for restrictions in EVAP system.

A fuel tank pressure sensor that does not correctly respond to pressure, or vacuum, causes this DTC to set.

© 2013 ALLDATA LLC. All rights reserved. Terms and Conditions

449

CIRCUIT DESCRIPTION
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.

CONDITIONS FOR RUNNING THE DTC

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

CONDITIONS FOR SETTING THE DTC

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.

ACTION TAKEN WHEN THE DTC SETS

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.

CONDITIONS FOR CLEARING THE MIL/DTC

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.

DIAGNOSTIC AIDS

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: Powertrain Management\Computers and Control Systems\Testing and Inspection\Symptom Related Diagnostic Procedures

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

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.
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 ).

Momentarily probe the solenoid control circuit to ground. Listen for an audible click when the solenoid operates.

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.

ASEMaster6371
Mar 22, 2013.