DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected. GMC Truck Sonoma Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 Sonoma Pickup - 4WD 🢒 DTC 🢒 DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected

Engine Controls Components
Cell 20: Fuel Level and Fuel Tank Pressure Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The evaporative system includes the following components:

•	The fuel tank

•	The EVAP vent solenoid

•	The fuel tank pressure sensor

•	The fuel pipes and hoses

•	The fuel vapor lines

•	The fuel cap

•	The EVAP canister

•	The purge lines

•	The EVAP canister purge solenoid valve

•	The EVAP service port

The evaporative emission (EVAP) system is checked by applying vacuum to the EVAP system and by monitoring for a vacuum decay. The Powertrain Control Module (PCM) monitors the vacuum level through the fuel tank pressure sensor signal. At an appropriate time, the EVAP canister purge solenoid valve and the EVAP vent solenoid are turned ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. Once the desired vacuum level has been achieved, the EVAP canister purge solenoid valve turns OFF, sealing the system. A small leak in the system will cause DTC P0442 to set.

Conditions for Running the DTC

•	No active MAP DTC's

•	No active IAT DTC's

•	No active ECT DTC's

•	No active TP DTC's

•	No active Oxygen Sensor DTC's

•	No active Fuel Tank Pressure DTC's

•	No active VSS DTC's

•	No active PCM Memory DTC's

•	The BARO is more than 75 kPa.

•	The Start-up ECT and IAT are between 4°C and 30°C (39°F and 86°F).

•	The Start-up ECT is less than 8°C (14°F) above Start-up IAT.

The Start-up IAT is less than 1.5°C (3°F) above Start-up ECT.

•	The fuel level is between 15 percent and 85 percent.

•	The TP sensor is between 7 percent and 35 percent.

•	The Vehicle Speed is less than 70MPH (113KPH).

•	The engine is running.

Conditions for Setting the DTC

The EVAP system is unable to hold vacuum during the diagnostic test.

Action Taken When the DTC Sets

•	The malfunction indicator lamp (MIL) will illuminate.

•	The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.

•	A history DTC stores.

Conditions for Clearing the MIL/DTC

•	The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs a pass.

•	A history DTC will clear after 40 consecutive warm up cycles without a malfunction.

•	A scan tool can clear the DTCs.

Diagnostic Aids

•	A loose, missing, or damaged fuel cap.

•	Missing or damaged O-rings at the fuel vapor fittings and the EVAP purge line canister fittings.

•	Cracked EVAP canister

•	Damaged source vacuum line, EVAP purge line, EVAP vent hose or fuel tank vapor line

•	Poor connection at PCM: Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

•	Damaged harness: Inspect the wiring harness to the EVAP vent solenoid, the EVAP purge solenoid, and the fuel tank pressure sensor for an intermittent open or intermittent short circuit.

Check for charcoal particles. Refer to Evaporative Emission System Cleaning before starting repairs.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that causes the DTC to set occurs. This may assist in diagnosing the condition.

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.

If a vent solenoid or an EVAP canister purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction will very likely correct the condition that set DTC P0442.

This step checks the fuel tank pressure sensor at the ambient pressure.

This step verifies that the fuel tank pressure sensor accurately reacts to the EVAP system pressure changes.

This step insures proper system integrity.

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Turn ON the ignition leaving the engine OFF.
Install a scan tool.

Is DTC P0452, P0453, P0460, P0462 or P0463 also set?

Go to applicable DTC table

Go to Step 3

Command the EVAP canister purge valve ON and OFF with the scan tool.
Command the vent solenoid ON and OFF with the scan tool.

Does the purge valve and vent solenoid click ON and OFF?

Go to Step 4

Go to Powertrain Control Module Outputs Diagnosis

Remove the fuel cap.
Observe the fuel tank pressure value on the scan tool.

Is the fuel tank pressure at the specified value?

-2.4 to 2.4 mmHg

(-1.28 to 1.28 in. H2O)

Go to Step 5

Go to

DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

Important: : Before continuing with this diagnosis, zero the EVAP Pressure and Vacuum gauges on the EVAP pressure/purge cart J 41413 . Then, read the temperature variation instructions. Refer to the tool operating instructions.

Reinstall the fuel cap.
Command the EVAP vent solenoid ON (closed) with the scan tool.
Connect the EVAP pressure/purge cart J 41413 to the EVAP service port.

Important: Do not exceed the pressure in the first specified value.

Pressurize the EVAP system to the first specified value using the EVAP pressure/purge cart J 41413 . Monitor the pressure by using the gauge on the cart with the switch in the HOLD position.
Observe the fuel tank pressure value on the scan tool.

Is the fuel tank pressure at the second specified value?

12 mmHg

(6.42 in. H2O)

7.2 to 16.8 mmHg

(3.85 to 8.99 in. H2O)

Go to Step 6

Go to

DTC P0452 Fuel Tank Pressure Sensor Circuit Low Voltage

DTC P0453 Fuel Tank Pressure Sensor Circuit High Voltage

Important: Review the temperature variation instructions included with the EVAP pressure/purge cart J 41413 before performing this step.

Command the EVAP vent solenoid ON (closed) with the scan tool.

Important: Do not exceed the pressure in the first specified value.

Pressurize the EVAP system to the first specified value by using the EVAP pressure/purge cart J 41413 . Monitor the pressure by using the gauge on the cart.
Switch the rotary switch on the cart to HOLD and observe the EVAP pressure gauge.

Does the pressure decrease to less than the second specified value within 2 minutes?

15 in. H2O

10 in. H2O

Go to Step 7

Go to Diagnostic Aids

Disconnect the fuel tank vapor line and the EVAP purge line from the EVAP canister.
Block the fuel tank vapor line fitting on the canister.
Connect a hand vacuum pump to the EVAP purge line fitting on the canister.
Ensure that the EVAP vent solenoid is still commanded ON (closed).
Attempt to apply vacuum to the canister to the specified value.

Can the specified vacuum be achieved and maintained?

5 in. Hg

Go to Step 10

Go to Step 8

Visually/physically check for the following conditions:

•	A disconnected or damaged vent hose

•	A damaged EVAP canister

If a problem is present, repair the problem as necessary.

Was a repair necessary?

Go to Step 12

Go to Step 9

Replace the EVAP vent solenoid. Refer to Evaporative Emission Vent Valve Replacement .

Is the action complete?

Go to Step 12

Visually/physically check for the following conditions:

•	A malfunctioning fuel cap

•	A leaking fuel tank vapor line

•	A damaged EVAP purge line

•	The quick connect O-rings for the EVAP lines.

If a problem is present, repair the problem as necessary.

Were there any necessary repairs?

Go to Step 12

Go to Step 11

Reconnect all the EVAP hardware that was previously disconnected.
Command the EVAP vent solenoid ON (closed) with the scan tool.
With the EVAP pressure/purge cart J 41413 connected to the EVAP system, leave the cart control knob in the pressurized position.
Using the ultrasonic leak detector J 41416 , locate and repair the leak in the EVAP system. It may be necessary to partially lower the fuel tank in order to examine the top tank connections.

Is the action complete?

Go to Step 12

Important: Review the temperature variation instructions included with the J 41413 EVAP pressure/purge cart before performing this step.

Reconnect all the EVAP hardware that was previously disconnected.
Turn ON the ignition switch leaving the engine OFF.
Command the EVAP vent solenoid ON (closed) with the scan tool.

Important: Do not exceed the pressure in the first specified value.

Pressurize the EVAP system to the first specified value by using the EVAP pressure/purge cart J 41413 . Monitor the pressure by using the gauge on the cart.
Switch the rotary switch on the cart to HOLD and observe the EVAP pressure gauge.

Does the pressure decrease to less than the second specified value within 2 minutes?

15 in. H2O

10 in. H2O

Go to Step 3

Go to Step 13

Clear the DTCs with the scan tool.
Start the engine.
Idle the engine at the normal operating temperature.
Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that the diagnostic ran and passed?

Go to Step 14

Go to Step 2

Check to see if any additional DTC are set.

Does the scan tool display any DTCs that you have not diagnosed?

Go to the applicable DTC table

System OK