Allpar Forums banner

1 - 3 of 3 Posts

·
Registered
Joined
·
122 Posts
Discussion Starter #1
Shooting wires for No Bus condition, tested O2 sensors.No cross wire shorts. Grounds are ground, sensor grounds only ground when connected to PCM, wires test fine. No Codes.


Manual says should read 0.1V for 2 min during open loop, then fluctuates between 0.1-0.9V once warmed up for closed loop.

Mine both read 0.01V-0V when cold.
Once warmed up:
Upstream (grey) fluctuates between 0.15V-0.96V
Downstream (black) fluctuates between 0.24V-1.04V


Are these values within tolerance? Calling out the sensors as bad? A sign of too lean/rich fuel?
Warmed up, upstream seems close to correct, downstream seems swayed just a bit.
0.01V to no volts for the first two minutes doesn't seem right at all though.
 

·
Super Moderator
Joined
·
21,351 Posts
Has it ever set O2 sensor fault codes? The PCM is a better tester of the O2 sensors than any manual test, which is more of a general test.
The downstream may straighten out after a long drive. See what its range is after it's hot and working for awhile. The downsteam O2 will change voltage up/down at about half the rate of speed than the upstream O2 sensor.
The O2's are inactive while cold, so I can't say whether 0 volts is bad or not. The PCM doesn't use the O2 sensor and the O2 heater should be on full until closed loop (~600°F/316°C) anyways, so I don't see the element cold test being a validation.
 

·
Registered
Joined
·
122 Posts
Discussion Starter #3
I just re-read it, its meant for scan tool voltage testing, not backprobing, so I couldn't test it right anyways.
I did also check the heater circuits. both were at 5.5ohms (5-7 good), so mostly alright.

There's no codes for them, they just share some voltages with other sensors that may be knocking out the bus, so anything that's not playing a long will have to go. These the first parts to stand out as iffy, so wanted to ask
 
1 - 3 of 3 Posts
Top