Somerset V6-181 3.0L (1986)
Wiring Diagram for Chart C-3 - Canister Purge Check
CHART C-3 - CANISTER PURGE CHECK
Circuit Description:
Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when energized. The ECM supplies a ground to energize the
solenoid (purge "ON").
If the diagnostic "test" terminal is grounded with the engine stopped or the following is met with the engine running the purge solenoid is energized
(purge "ON").
^
Engine run time after start more than 1 minute
^
Coolant temperature above 80~C (176~F)
^
Vehicle speed above 5 mph (8 km/h)
^
Throttle "OFF" idle. TPS signal above .75 volt
Test Description:
Numbers below refer to circled numbers on the diagnostic chart.
1.
Checks to see if the solenoid is opened or closed. The solenoid is normally de-energized in this step, so it should be closed.
2.
Completes functional check by grounding "test" terminal. This should normally energize the solenoid and allow the vacuum to drop (purge "ON") .
3.
Checks for open or shorted solenoid circuit.
4.
Checks to see if ECM control circuit or solenoid is at fault.
Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM. Using an ohmmeter, check the purge
solenoid, coolant fan relay resistance before installing a replacement ECM, because they could cause failure of the purge circuit.
5.
Checks to see if the short to voltage damaged original ECM.
