No Self-Test Output
1) Ensure jumper wire is disconnected from Self-Test Trigger in self-test connector. Disconnect harness connector at MCU. Connect a voltmeter between pins No. 14 and 20 in harness connector. See Fig 1 . With ignition on, 10.5 volts or more should be present. If so, go to step 3. If not, go to next step.
2) Connect voltmeter between pin No. 20 and ground. If voltage reading is more than 10.5 volts, repair circuit from pin No. 14 to ground, and retest. If voltage reading is not 10.5 volts, repair circuit from pin No. 20 to battery and retest.
3) With ignition off, check continuity of circuit from self-test connector (Black/Light Green wire) to ground. If resistance is less than 1 k/ohm, go to next step. If resistance is greater than 1 k/ohm, repair circuit.
4) Check continuity between MCU harness connector Pin No. 19 and Self-Test Trigger terminal (Tan/Red wire). See Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair circuit, and retest.
5) Check continuity between harness connector Pin No. 8 and "Tach Test" terminal at coil "horseshoe" connector (connector removed). See Fig 1 . If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair circuit and retest.
6) Disconnect harness connector at canister purge solenoid. Check continuity between MCU connector Pin No. 9 and Gray/Yellow wire at canister purge connector. Check resistance between Pin No. 20 and Gray/Yellow wire. If resistance of each circuit is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair circuit and retest.
7) Connect ohmmeter across canister purge solenoid. Resistance should be 50-100 ohms. If not, replace solenoid. Retest. If no service code is present, replace MCU. If resistance is within specifications, go to next step.
8) Connect ohmmeter between engine ground and Gray/Yellow harness wire at canister purge solenoid. If resistance is less than 1 k/ohm, go to next step. If resistance is greater than 1 k/ohm, repair short circuit to ground, and retest.
9) 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, and retest. If not, replace solenoid and retest.