1999 SAAB 9-3 repair Question Heater circuit malfunction on

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Start by checking fuse #38 in dashboard fuse box ?

DTC P0135: FRONT HEATED OXYGEN SENSOR (HO2S-1) PREHEATING
With ignition off, connect TECH 2 scan tool to DLC. Turn ignition on. Contact TRIONIC 5 OBD II. Check for stored DTCs. If DTC P0141 has not been set, go to step 3 . If DTC P0141 has been set, check fuse No. 38 in dashboard fuse block. See Fig. 6 . If fuse is defective, replace fuse and go to step 5 . If fuse is okay, connect SST 86 11 857 test light (or equivalent) between upper terminal of fuse No. 38 and ground. Go to next step.
Use scan tool to select ACTIVATE: MAIN RELAY. If test light does not flash, repair faulty circuit between fuse No. 38 and crimped connector J76 (Grey/Red wire). See appropriate wiring diagram in WIRING DIAGRAMS article. If test light does flash, turn ignition off for at least 5 minutes. Unplug HO2S-1 and HO2S-2 connectors. Use DVOM to measure resistance between HO2S connector terminals No. 1 and 2 (both White wires) on each sensor. See Fig. 5 . Both readings should indicate 1.8-4.0 ohms. If either sensor value is not as specified, replace faulty HO2S sensor. See HO2S SENSORS under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION article. If both sensor values are as specified, check for faulty circuit between fuse No. 38 and HO2S harness connector terminals No. 1 of each sensor (Grey/White wire). Repair as necessary. Go to step 5 .
Unplug HO2S-1 electrical connector. Connect SST 86 11 857 test light (or equivalent) between HO2S-1 harness connector terminal No. 1 (Grey/White wire) and ground. Use scan tool to select ACTIVATE: MAIN RELAY. If test light does not flash, repair faulty circuit between HO2S-1 harness connector terminal No. 1 and fuse No. 38 (Grey/White wire) in dashboard fuse block. If test light does flash, go to next step.
Connect test light between HO2S-1 harness connector terminal No. 2 (Black/White wire) and battery positive terminal. Use scan tool to select ACTIVATE: O2S 1. If test light does not light, repair faulty circuit between HO2S-1 harness connector terminal No. 2 and ECM harness connector terminal No. 50 (Black/White wire). If test light does light, replace HO2S-1. Go to next step.
Use scan tool to clear DTCs. Drive vehicle for 5 minutes under varying loads and engine RPM. Recheck for any stored DTCs. If DTC P0135 is present, substitute known good ECM and retest system. See ENGINE CONTROL MODULE (ECM) under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article.

hope this helps

Any auto parts store will be able to provide you with the correct type and brand replacement O2 sensor for you saab. Thank you for your donation and we look forward to helping you in the future.