5.7 Vortec O2 sensors reporting accurately?
09-05-2019, 03:08 PM
#1
TECH Apprentice
Thread Starter
5.7 Vortec O2 sensors reporting accurately? Hi guys, I'm hoping someone can help me with this one. I've got a 2000 5.7 Vortec on a K3500. I hardly drive it, and has given me P0174 Lean Code Bank 2 and also (sometimes) P0157 HO2S circuit low voltage bank 2 sensor 2 for the last year.
It seems to idle just fine and acceleration seems fine also. Basically, seems to drive fine. I've checked fuel pressure and was about 62 psi and didn't drop after 15 minutes.
A few months ago I tried to check for vacuum leaks at the intake by using a homemade smoke machine hooked up to the air inlet hose. Just had a small leak on the EGR valve, but swapped to another valve and it did the same. Was hoping to find the common intake manifold gasket leak, but didn't leak.
Last night I checked with a multimeter the O2 sensors and got the following:
Bank 2
Sensor 1 (upstream)
At idle: Min. 0.228V
Max. 0.810V, more or less alternating between 0.3V and 0.7V
If I give it a short burst of gas voltage changes to 0.10V
After gas let-go the voltage goes to 0.90V
Sensor 2 (downstream)
0.500V, pretty steady.
Basically, what I'm asking is the O2 sensors seem to be reporting low and high voltages, so I don't think they are the culprit, but don't give the 0.1V to 0.9V they should. Just wanted to check with someone that know more about this than me, before buying new ones.
It seems to idle just fine and acceleration seems fine also. Basically, seems to drive fine. I've checked fuel pressure and was about 62 psi and didn't drop after 15 minutes.
A few months ago I tried to check for vacuum leaks at the intake by using a homemade smoke machine hooked up to the air inlet hose. Just had a small leak on the EGR valve, but swapped to another valve and it did the same. Was hoping to find the common intake manifold gasket leak, but didn't leak.
Last night I checked with a multimeter the O2 sensors and got the following:
Bank 2
Sensor 1 (upstream)
At idle: Min. 0.228V
Max. 0.810V, more or less alternating between 0.3V and 0.7V
If I give it a short burst of gas voltage changes to 0.10V
After gas let-go the voltage goes to 0.90V
Sensor 2 (downstream)
0.500V, pretty steady.
Basically, what I'm asking is the O2 sensors seem to be reporting low and high voltages, so I don't think they are the culprit, but don't give the 0.1V to 0.9V they should. Just wanted to check with someone that know more about this than me, before buying new ones.
