No Self-Test Output
Disconnect jumper wire from Self-Test Trigger in Self-Test connector.
- Disconnect harness connector at MCU. Connect a voltmeter between pins 14 and 20 in MCU connector. With ignition on, 10.5 volts or more should be present. If so, go to step 3). If not, go to next step.
- Connect voltmeter between pin 20 and ground. If voltage is now more than 10.5 volts, repair circuit from pin 14 to ground. If not, repair circuit from pin 20 to battery.
- With ignition off, check continuity of circuit from Self Test Connector (Blk/Lt Grn) to ground. If resistance is less than 1,000 ohms, go to next step. If not, repair circuits.
- Check for continuity between MCU connector pin 19 and Self-Test Trigger socket (Tan/Red). If resistance is less than 5 ohms, go to next step. If not, repair circuit.
- Check continuity between MCU connector pin 8 and "Tach Test" lead at coil "horseshoe" connector (remove connector from coil). If resistance is 5 ohms or less, go to next step. If not, repair circuit.
- Disconnect canister purge connector. Check continuity between MCU connector pin 9 and Gry/Yel Hash wire at canister purge connector. Also check between pin 20 and Gry/Yel Stripe wire. If resistance of each circuit is less than 5 ohms, go to next step. If not, repair circuits.
- Connect ohmmeter across canister purge solenoid. Resistance should be 50-100 ohms. If not, replace solenoid. If so, go to next step.
- Connect ohmmeter between engine ground and Gry/Yel Hash wire at canister purge solenoid. If resistance is greater than 1000 ohms, go to next step. If less, repair short circuit to ground.
- Check to ensure canister purge solenoid passes vacuum when energized with 12 volts, and blocks vacuum when de-energized. Check housing for leaks. If solenoid is okay, replace MCU module. If not, replace solenoid and retest.