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My 99 Camry appear to have weird ST data stream. I understand bank 1 sensor 1 (B1S1) voltage fluctuate very often, while (B1S2) should remain fairly steady for proper fuel trim operation in closed loop mode. However, this care appear to have reversed the sensors as the (B1S1) remains fairly steady at 0.66V while B1S2 fluctuate instead. Could a bad cat. Be responsible.
See attachment for data stream graphs
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The third graph, labeled “trim”, looks like a healthy upper O2 sensor’s voltage. I have misgivings about what these graphs actually represent versus what they’re labeled, but first – what symptoms of the car’s performance have led you to this research?
@relative4, the graphs are live data from obd scan tool. First graph is up stream O2 sensor voltage, second is down stream O2 sensor voltage, while the third is the up stream sensor short term fuel trim (STFT). No STFT data is produced for down stream O2 sensor. I may be wrong, but I expect down stream sensor voltage to remain fairly steady, while the up stream should fluctuate instead. However, it seems both sensors have reversed role instead. The one to fluctuate is steady, and vise versa. Is this normal. By the way, the car’s MIL is ON with DTC P0401 pending & P1133 store ( I replace the up stream O2 sensor part no ending with 33011 with another end with 33040 when the heater failed). It use to have P0446 as well but it went away after I replace the vent solenoid. The engine run steady but kind of trembles badly when idling. I’ve tried doing a rough calculation of the gas millage and it drinks about 5.5gal for 130 mile on the highway (I.e about 24 mpg).
I want the engine to idle steadily and the DTC codes issue to be addressed. When I kick down on the gas pedal, I don’t get power as it used to be; and its usually accompanied with a buzzing like sound from underneath.
Help will be appreciated.
ThanksSecond and third chart looks normal as relative4 said. They are proportionate to each other in voltage which, if the engine is to temp is indicative of a CAT that is not working properly. This means that the cat is not doing its job and the S2 sensor is saying the same thing as the S1 sensor. That however should cause a P0420 if driven far enough….
The issue with the P1133 should not have anything to do with the above. Have you checked your fuses and Relays for the O2 sensors? While it appears they are getting voltage, there may be an issue with it heating up…
Also, is this a California emissions vehicle?
Good luck
-Karl
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