o2 sensor open loop
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New User
Joined: Sep 2012
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o2 sensor open loop
Hi guys.
New o2s, new ex manifold/ gasket, no codes?, and i built a homemade smoke machine . Found nothing.
I get no voltage reading on scan tool. Old sensor gave reading only with throttle down. New sensor no reading at all.
No codes. Seems like its in open loop. Or maybe wiring was messed with.
Anyone know where to start trouble shooting?
Did all this work and still ****ty gas mileage.
1999 e150 4.2
Thanks
Any help is appreciated!
New o2s, new ex manifold/ gasket, no codes?, and i built a homemade smoke machine . Found nothing.
I get no voltage reading on scan tool. Old sensor gave reading only with throttle down. New sensor no reading at all.
No codes. Seems like its in open loop. Or maybe wiring was messed with.
Anyone know where to start trouble shooting?
Did all this work and still ****ty gas mileage.
1999 e150 4.2
Thanks
Any help is appreciated!
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
All I can do at this point is tell you what is supposed to be!
There is a harness down the passenger side of the motor and back to the trasmission, OX sensors and EVAP system.
There is a single fuse #23 that feeds all these points.
The OX sensors have a 12 volt feed to their heaters.
The sensor outputs are dedicated back to the PCM.
.
If your sure you have no codes set and the CEL is not on, there is no trouble or the PCM would pick it up in a short time of driving.
The PCM looks at the heater circuit, the outputs of the sensors and all the other poins the harness feeds.
Each of these have there own codes.
.
Maybe the scanner is not telling you the truth.
Normally a scanner can see the outputs of the OX sensors swinging, the short term fuel table values and the long term table values so you have a lot of data to see an issue not just the sensor outputs.
Take a new look at the situation and decide what you have.
Once you reboot the PCM with a power down it take a number of drive cycles to get back to tour driving style as detected by the PCM
Good luck.
There is a harness down the passenger side of the motor and back to the trasmission, OX sensors and EVAP system.
There is a single fuse #23 that feeds all these points.
The OX sensors have a 12 volt feed to their heaters.
The sensor outputs are dedicated back to the PCM.
.
If your sure you have no codes set and the CEL is not on, there is no trouble or the PCM would pick it up in a short time of driving.
The PCM looks at the heater circuit, the outputs of the sensors and all the other poins the harness feeds.
Each of these have there own codes.
.
Maybe the scanner is not telling you the truth.
Normally a scanner can see the outputs of the OX sensors swinging, the short term fuel table values and the long term table values so you have a lot of data to see an issue not just the sensor outputs.
Take a new look at the situation and decide what you have.
Once you reboot the PCM with a power down it take a number of drive cycles to get back to tour driving style as detected by the PCM
Good luck.
Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
I don't know why you're not reading the O2 sensor, but I'm pretty sure that it's working.
If it wasn't you'd be getting a code. O2 sensors switch between high and low constantly, and the pcm checks to see if the switch count is high enough.
You MIGHT have an issue with a temp sensor. If the pcm thought that the engine was staying cold, it would stay in open loop. Newer ones will complain if ithey never get a normal temp, but I'm not sure when that started.
Does your scanner show Engine Coolant Temp(ECT) ?
Just a thought,
hj
If it wasn't you'd be getting a code. O2 sensors switch between high and low constantly, and the pcm checks to see if the switch count is high enough.
You MIGHT have an issue with a temp sensor. If the pcm thought that the engine was staying cold, it would stay in open loop. Newer ones will complain if ithey never get a normal temp, but I'm not sure when that started.
Does your scanner show Engine Coolant Temp(ECT) ?
Just a thought,
hj
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