nsghtbrwry

Sometimes the Bosch is a rebranded/reboxed NGK - those are OK. Avoid the actual Bosch sensors, they're garbage. The Denso is an exact match for the OEM sensor (which is made for Toyota by Denso). As listed before, you actually have three: two before the cats (one on each bank, same sensors) and one after the cats. Keep in mind that Bank 1 is the rear bank.

JCC511

I really appreciate the help. I also need to determine if I need to change out the other sensors that seem to be throwing codes(air fuel sensor, engine coolant temperature sensor and shift solenoid E).

nsghtbrwry

Maybe a larger electrical problem as has been stated.

You can test the engine coolant temp sensor with a multimeter. The two upstream O2 sensors are A/F sensors, and the downstream one is a plain-jane heated O2 (HO2S).

JCC511

When testing the engine coolant sensor, what value am I looking for? I would prefer not to have to replace all three O2 sensors and the engine coolant sensor. I will do what I need to.

nsghtbrwry

See attached. Remember that the ECT sender has two terminals; the one-terminal sender is for the temp gauge only.

As for your sensors:

- if your catalyst monitor is not ready, that doesn't necessarily mean that the rear O2 sensor is bad. Wait until it throws a P0420 (catalyst below efficiency threshold) or similar before addressing that
- check your codes again. 90% of the time, there will be a code pointing to the sensor that needs replacing. If they're very old, they will be lazy and should be replaced anyway
- if the shift solenoid codes come back after clearing, I would address those. The A541E transmission is pretty bulletproof, but that doesn't mean stuff doesn't break or it doesn't need maintenance. When was the fluid last drained and refilled?

JCC511

Transmission fluid? Possibly has not been done. I have not done it and I have had the car for almost two years. I was thinking of disconnecting the O2 sensors to see if those codes clear. I need to get the inspection/registration done before I get a ticket.

nsghtbrwry

? Disconnecting the O2 sensors will make sure codes set for sure!

JCC511

Disconnecting them will throw codes?

anniverse

I have Lexus GS300 Gen2 1999.
I took the ECT sensor out and found some oxidation and
electrolysis powder stuff on it but I had to check it anyway.
I measured with a Fluke Multimeter and had a reading of
around 830 to 860 and not sure. after heating it boiling it
it started to drop to almost zero.
I have 127,000 miles so went ahead and changed it.
The original had Part # 89422-30030 and I paid $1118.00 at
Toyota. It was done last week and the first thing I noticed
was the smooth idling at around 600 rpm and around 300 rpm
when shifted to Drive

SoCalSC4

This needs to be smogged. But still runs great. Took it for a quick spin about two weeks ago.