Evaporative Emissions System: Testing and Inspection

Purge Solenoid Circuit Diagram:

CANISTER PURGE VALVE CHECK

CIRCUIT DESCRIPTION:

The canister purge is controlled by a solenoid that allows vacuum to purge the fuel vapor canister when energized. The PCM controls the ground to power the solenoid. If the diagnostic test terminal is grounded with the engine not running, or the following exist with the engine running, the purge solenoid is energized:

1. The engine run time is more than 20 seconds on a warm engine and 2.5 minutes on a cold engine.
2. The coolant temperature is above 60~C (140~F).
3. The outside air temperature is above 9.5~C (49~F).

Purge Solenoid Diagnostic Chart (Chart C-3):

TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. This checks to see if the solenoid is opened or closed. It should be closed (de-energized).
2. This completes a functional check by grounding the test terminal. This should normally energize the solenoid and allow the vacuum to drop.

NOTE: Once the test sequence is completed, clear codes and verify NO "SERVICE ENGINE SOON" light exists.

CAUTION: Not all "SCAN" testers are compatible with every system. A "SCAN" tool that produces faulty readings should NOT be used, and the problem should be reported to the tool manufacturer. Use of a faulty "SCAN" tool can result in improper diagnosis and unnecessary component replacement. Follow the proper instructions, located in the owners manual, for the specific "SCAN" tool being used.


INCORRECT OPERATION MAY CAUSE:

1. Poor idle, stalling and poor driveability. Check for:

a. Inoperative or defective purge valve or solenoid
b. Damaged canister
c. Hoses split, cracked or not connected to the proper tubes
d. Pinched or plugged hose(s).


2. Evidence of fuel loss or fuel vapor odor. Check for:

a. Liquid fuel leaking from fuel lines, fuel pump, or injectors
b. Cracked or damaged canister
c. Inoperative canister control valve
d. Disconnected, misrouted, kinked, deteriorated or damaged vapor hoses, or control hoses
e. If the solenoid is always open, the canister may purge all the time. This can allow extra fuel at idle or during warm-up, which can cause a rough idle or a rich operation
f. If the solenoid is always closed, the canister can become over-loaded, resulting in fuel odor.