Component Diagnostic Charts - Throttle Body Fuel Injection

Fig. 097 - Wiring Diagram for Chart C-3 Canister Purge Valve. VIN P:

CHART C-3, CANISTER PURGE CHECK

Canister purge is controlled by a solenoid that allows manifold vacuum to purge the canister when de-energized. The ECM supplies a ground to energize the solenoid (purge off).
If the diagnostic test terminal is grounded with the engine stopped or the following is met with the engine running the purge solenoid is de-energized (purge on).
a. Engine run time after start more than 1 min.
b. Coolant temperate above 80°C
c. Vehicle speed above 5 mph.
d. Throttle off idle. TPS signal about .75 volt.

Fig. 096 Chart C-3 Canister Purge Valve:

1. Checks to see if the solenoid is opened or closed. The solenoid is normally energized in this step; so, it should be closed.
2. Checks for a complete circuit. Normally there is battery voltage on CKT 39 and the CKT 39 and the ECM provides a ground on CKT 428. A shorted solenoid could cause an open circuit in the ECM.
3. Completes functional check by grounding test terminal. This should normally de-energize the solenoid and allow the vacuum to drop (purge on).
4. Solenoids or relays turned "ON" of "OFF" by the ECM internal electronic switches called "drivers". Each driver is part of a group of four called "Quad-Drivers". Failure of one can damage any other driver within the set.
Solenoid coil resistance must measure more than 20 ohms. Less resistance will cause early failure of the ECM "DRIVER". Using an ohmmeter, check the solenoid coil resistance of the following before installing a replacement ECM.
a. Canister Purge.
b. EGR Solenoid
c. A/C Control Relay Coil - opposite harness connector terminals "B and C"