Computer problem
1999 Subaru Outback 4 cyl All Wheel Drive Automatic 104000 miles
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Check Engine appears indicating PO 135 Code (Front 02 sensor heater-irregular voltage) only after engine is re-started after initial warm up. When cold and continual usage-No Check Engine Light. Swapped both 02 sensors (Front & rear)(denso brand). Car runs perfect with or without check engine light on.
Some investigations include a potential bad (or shorted) ECM however everything runs just fine. If it was a potential grounding problem, why does check engine light remain off until I shut engine down and immediately re-start while is engine is warm ? Perplexing huh ? Engine is 2.5 litre A/T Would appreciate your thoughts...

Thanks,

Gordon
Venice FL

check the voltage at the main relay (behind left side of dash) red and yellow/red wires.there are basically 2 relays biuilt into 1 inside that and the o2 sensors are fed power off the yellow/red wire,the red is power into the relay, the relay may be faulty and not giving good voltage consistantly