Procedure "A"
- Turn ignition off. Loosen and retighten engine ground bolts. See Figure. Disconnect AP sensor harness connector. See Figure. Turn ignition on. Measure voltage between AP sensor harness connector Pink/Black wire and ground. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, repair open or short in Pink/Black wire.
- Turn ignition off. Check continuity between AP sensor harness connector Black wire and ground. If continuity exists, go to next step. If continuity does not exist, repair open in Black wire.
- Disconnect ECM harness connector. See Figure. Check continuity of Green/White wire between ECM harness connector terminal No. 45 and AP sensor harness connector. See Figure. If continuity exists, go to next step. If continuity does not exist, repair open in Green/White wire.
- Reconnect all harness connectors. Remove AP sensor from its bracket and disconnect vacuum hose. Turn ignition on. Measure voltage between ECM harness connector terminal No. 45 and ground by backprobing. Voltage should be 3.2-4.8 volts. Using a hand vacuum pump, apply 7.87 in. Hg of vacuum to AP sensor. Voltage should be 1.0-1.4 volts less than voltage measured with no vacuum applied. Voltage should decrease as vacuum is applied. See Fig 1. If voltage is not as specified, replace AP sensor. If voltage is as specified, go to next step.
- Check shield circuit for continuity to ground. Shield is connected to ground through connector F-21 (Blue, 12-pin joint connector located near ECM). See appropriate wiring diagram in WIRING DIAGRAMS article. If continuity does not exist, repair open circuit. If continuity exists, no problem is currently indicated. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.