I hate to state the obvious, but was the voltmeter hooked up correctly to the O2 sensor, i.e. correct polarity?

 

I hate to state the obvious, but was the voltmeter hooked up correctly to the O2 sensor, i.e. correct polarity?

I hooked it up the same way as the bank 1 sensor, i used the connector that just crimps on 2 wires one being the blue wire to O2 sensor the other wire i ran to my volt meter with another connecter.
its a ghetto way to test it seems to work the other side worked fine. and it went from -.10 to like -.90 pretty quick when i cranked the engine one.

 

I hooked it up the same way as the bank 1 sensor, i used the connector that just crimps on 2 wires one being the blue wire to O2 sensor the other wire i ran to my volt meter with another connecter.
its a ghetto way to test it seems to work the other side worked fine. and it went from -.10 to like -.90 pretty quick when i cranked the engine one.

The best way to measure a voltage is directly across the O2 sensor, both power and ground. It might have been that you did not have the ground connection hooked close to the actual O2 sensor ground, but rather a ground some distance away from the O2 sensor. You mention taking this measurement while cranking (starting) the engine. When turning the engine over, lots of current flows. It might have been that a small portion of this current was using that same ground as partial return path to the battery, thus causing a voltage drop that added to the actual O2 sensor voltage that you were tying to measure. This may have caused the erroneous voltage you measured.

Firstly it is best to measure voltages as much as possible directly across the sensor you are trying to read. Secondly, do not take the reading while turning the engine over...wait until the engine is running and the O2 sensor gets a good heat soak.

 

Firstly it is best to measure voltages as much as possible directly across the sensor you are trying to read. Secondly, do not take the reading while turning the engine over...wait until the engine is running and the O2 sensor gets a good heat soak.

sorry i ment while engine running is when i watched the reading go from -10 to -90volts. what do you mean directly across the sensor? the ground was far way so ill try closer, but my engine light is on again same P0125 code. so i want to diagnosis a bad O2 sensor instead of just replacing it, know what i mean haha.

 

Anybody know what P0125 means?

 

Per Toyota Service Manual
P0125
Page: (DI-233)
Description: Insufficient Coolant Temperature for Closed Loop Fuel Control
Affected System(s): Cooling system, Engine coolant temp. sensor

Ignore the description. It is a bad heater element in the sensor unit. Replace. Don't bother with spending effort to "diagnose" with voltmeters.

See this thread for more posts on the problem and remedy: http://www.tundrasolutions.com/forums/1gen-tundra/105048-code-po125/

 

Anybody know what P0125 means?

Insuffient coolant temp for closed loop operation fuel control, something like that, its the O2 sensor not reading at least .45v under 4 conditions blah blah basically it needs to reach .45 v after 180 secs. Bank 1 does bank 2 -.90v, my thermostat and temp gauges are working fine, this is an ongoing issue, theres a long story but ive read alot on it.
i just need to know what does -Volts reading mean?
thankyou for your replies.:ts:

 

I just use the old pc version of the Scangauge to display the live voltages on the sensors. If the computer says its bad, I just replace it regardless is I can see the fault.

Just how loud are those valves?

Some say, "happy valves are tappy valves".

Ive had luck putting synthetic in my sportbike and synthetic blend in my Tundra to quiet those pesky valves.

 

I just use the old pc version of the Scangauge to display the live voltages on the sensors. If the computer says its bad, I just replace it regardless is I can see the fault.

Just how loud are those valves?

Some say, "happy valves are tappy valves".

Ive had luck putting synthetic in my sportbike and synthetic blend in my Tundra to quiet those pesky valves.

they are noticable, i have a 99 accord and its pretty much the same way, i didnt know toyota practices the same motto.

 

1)i was wondering if there is a valve adjustment on the engine?
I havent bought a manual yet, the valves are ticking pretty loud on acceleration. oil pressure seems fine.

there is an adjustment, but you will need shims. there are "buckets" that sits on top of the valve. and on top of that "bucket" there is a place where you can remove the shim and put another one on there. it's pretty time consuming. when you check and see that it's too tight, lets just say specs are .006"-.008", and it measures .004" (with feeler gauges), you will have to remove that shim, measure how think that shim it and get another shim that is smaller. you will then need a shim that is smaller than the old one by at least .002" .004" minus .002" equals .002". so when you go back and install the .002" shim on the bucket, it will now be within specs. the smaller the shim you put in there, the wider the gap. don't know if i make any sense now.