Test TC-32A - Upstream O2 Sensor Stays At Center

NOTE: For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS article.

Start engine and warm engine to normal operating temperature. With scan tool in ACTUATOR TESTS mode, set engine speed at 1500 RPM. With scan tool in SENSORS mode, read upstream oxygen sensor state.
If upstream oxygen sensor state switches, go to next step. If upstream oxygen sensor state does not switch, go to step 7.
Wiggle wiring harness and connector at upstream oxygen sensor while monitoring upstream oxygen sensor state on scan tool. Upstream oxygen sensor is mounted on exhaust manifold.
If upstream oxygen sensor state does not become locked at center while wiggling wiring harness, go to next step. If upstream oxygen sensor state becomes locked at the center while wiggling wiring harness, repair open circuit in wiring harness or connector as necessary. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES .
Conditions required to set DTC are not present at this time. DTC may be stored in Powertrain Control Module (PCM) if upstream oxygen sensor voltage is between .35 volt and .55 volt for 1.5 minutes. Possible causes are: sensor signal circuit open, defective upstream oxygen sensor, defective PCM, dirt/moisture or grease causing voltage tracking in connector, defective connector terminals or wiring. Go to next step.
Check for defective wiring or connections at upstream oxygen sensor and PCM. The PCM is located between driver's side front fender and power distribution center, near battery. If defective wiring or connections exist, repair as necessary. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES . If no defective wiring or connections exist, see INACTIVE TROUBLE CODE CONDITION . Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES .
Turn ignition on with engine off. Disconnect connector at upstream oxygen sensor. Upstream oxygen sensor is mounted on exhaust manifold. Using ohmmeter, check resistance between ground and terminal No. 3 (Black/Light Blue wire) on wiring harness side of connector for upstream oxygen sensor.
If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open circuit in Black/Light Blue wire between upstream oxygen sensor and Powertrain Control Module (PCM). Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES . The PCM is located between driver's side front fender and power distribution center, near battery.
Connect jumper wire between terminal No. 4 (Black/Dark Green wire) on wiring harness side of connector for upstream oxygen sensor and positive battery terminal. Using scan tool, read upstream oxygen sensor voltage.
If upstream oxygen sensor voltage is one volt or less, go to next step. If upstream oxygen sensor voltage is more than one volt, replace upstream oxygen sensor. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES .
Turn ignition off. Disconnect connectors from Powertrain Control Module (PCM). The PCM is located between driver's side front fender and power distribution center, near battery.
Disconnect jumper wire from wiring harness side of connector for upstream oxygen sensor and positive battery terminal. Using ohmmeter, check resistance between terminal No. 4 (Black/Dark Green wire) on wiring harness side of connector for upstream oxygen sensor and PCM connector terminal No. 30 (Black/Dark Green wire).
If resistance is less than 5 ohms, replace PCM. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is 5 ohms or more, repair open circuit in Black/Dark Green wire between PCM and connector for upstream oxygen sensor. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES .