1999 Toyota Avalon Calf. w/Check Engine Light - Codes P0125 and P1133

edge

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#1
The car above car has 19K miles with no drivability problems. MIL is on, a scan shows the following codes P0125 Insufficient Temp for closed Loop and Pending Code P1133 A/F sensor Circuit response Bank 1/Sensor 1 . I am told that is a common code for a bad A/F sensor at Bank 1/ Sensor 1 and the A/F sensor should be replaced. Would like some input on this. Is there a way to check the A/F sensor like an O2 sensor with a DVOM? I checked the Heater voltage from the ECM with the A/F sensor unplugged, ignition on and engine off and read 9. 6 V, while V Batt was 12. 0. If a check on the sensor can't be done, it is a good bet the sensor is bad?
 

csaxon

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#2
The a/f sensor on your car was replaced with a newer design in Feb 2000 after complaints of erroneous P1133's showed up. Your's may be valid though. The P0125 can also be caused by running out of fuel, but I suspect it's related to the P1133.
 

edge

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Thanks for the test spec. Is there any spec to measure A/F signal that goes to the ECM? Do you know if the replacement of the new sensor was listed on a TSB ? I would guess the warranty has run out by now unless written in the TSB.
 

csaxon

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#5
The warranty ran out long ago. You'll need an obdii 2 scan tool that can display active a/f sensor output with the engine running to get output voltage readings. It can't be done from the terminals because the ecm + is fixed at 3.3v and the - is fixed at 3.0v.
If you run the heater resistance inspection I gave above and it fails, then replace the sensor.