Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . Turn ignition off. Disconnect ECM connector B136 (30-pin connector) and front HO2S connector. Using an ohmmeter, measure resistance of harness between specified ECM terminals and front HO2S harness terminals. See Figure and Figure
. See ECM-TO-FRONT HO2S CONNECTOR TEST TERMINALS - FORESTER, IMPREZA 2.5L & LEGACY & OUTBACK 2.5L A/T table. If resistance is less than one ohm at all points, go to next step. If resistance is not less than one ohm at all points, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and front HO2S. See WIRING DIAGRAMS article.ECM-TO-FRONT HO2S CONNECTOR TEST TERMINALS - FORESTER, IMPREZA 2.5L & LEGACY & OUTBACK 2.5L A/T
| ECM Connector B136 Terminal No. |
Front Oxygen Sensor Connector Terminal No. |
| 6 |
1 |
| 7 |
6 |
| 19 |
3 |
| 20 |
4 |