Test TC-155A - Upstream O2 Sensor Shorted To Ground
NOTE:
For connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS
article.
- This Diagnostic Trouble Code (DTC) may be stored in Powertrain Control Module (PCM) if upstream oxygen sensor signal voltage is less than .078 volt prior to upstream oxygen sensor heater test, and upstream oxygen sensor signal voltage is less than .078 volt after ignition is turned on in subsequent start. Possible causes are: dirt/moisture or grease on connector causing voltage tracking, sensor signal wire shorted to another circuit, defective upstream oxygen sensor, defective connector terminals or wiring, defective PCM. Upstream oxygen sensor is mounted on the exhaust manifold. Go to next step.
- Turn ignition on with engine off. Using scan tool, monitor upstream oxygen sensor voltage for a few minutes. Wait 3 minutes or until upstream oxygen sensor voltage stabilizes, and then note upstream oxygen sensor voltage.
- If upstream oxygen sensor voltage is less than .078 volt, go to next step. If upstream oxygen sensor voltage is .078 volt or more, conditions required to set DTC are not present at this time. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES .
- Turn ignition off. Disconnect connector at upstream oxygen sensor. Turn ignition on. Using scan tool, monitor upstream oxygen sensor voltage.
- If upstream oxygen sensor voltage is less than .078 volt, go to next step. If upstream oxygen sensor voltage is .078 volt or more, replace upstream oxygen sensor. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES .
- Turn ignition off. Disconnect connectors from PCM. The PCM is located between driver's side front fender and power distribution center, near battery.
- Using ohmmeter, check resistance between terminals No. 3 (Black/Light Blue wire) and No. 4 (Black/Dark Green wire) at wiring harness side of connector for upstream oxygen sensor. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short between Black/Dark Green wire and Black/Light Blue wire from PCM to upstream oxygen sensor. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES .
- Using ohmmeter, check resistance between ground and terminal No. 4 (Black/Dark Green wire) at wiring harness side of connector for upstream oxygen sensor. If resistance is 5 ohms or more, replace PCM. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES . If resistance is less than 5 ohms, repair short to ground on Black/Dark Green wire between PCM and upstream oxygen sensor. Perform TEST VER-5A - ROAD TEST FOR OBD-II TROUBLE CODES .