I believe it to be a bad bank one oxygen sensor question is,is it upstream or downstream and is the downstream sensor the one behind the engine.P1135 tells me its a fuel sensor heating circuit malfunction
Lexus Q&AAsk Your Question
1999 Lexus ES300 Question: I have error codes on a es300 of PO300,PO301,PO303,PO305 and P1135
Answer #1Kool Tool November 10, 2013, 09:54Rookie
Replace both unless you had one changed recently, they function as a unit. Clear codes after installation one fault code will set other codes when it becomes a fuel and air issue. (which it does.) If you don't have a scan tool, stop by any Auto Zone, Advance Auto Parts etc. and they should do it free of charge. Good Luck, Kool Tool. Downstream is the lower one.
Answer #2ziptie12 November 10, 2013, 19:21Master
Find and fix the cause of the misfire first , maybe???? And replace the O2 sensor with the faulty heater.
lightsaber November 12, 2013, 15:39Technician
Upstream between the engine and firewall. P0300 - P0305 = misfires on cylinders 1, 3, & 5. Along with replacing the O2 sensors, you might clean or replace the Variable Valve Timing oil control valve filters.