85 - Remains in "open loop".
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From: Crestwood Mo
85 - Remains in "open loop".
Have been here before. Engine will not go into closed loop. Had similiar problem before and found it to be a defunct knock sensor. This time I again am getting voltage from the ECM , .379 volts.Manual indicates the possibility of a bad ECM. Changed the ECM with a rebuilt, same results. Scanned the O2 sensor and found it to be functioning but the O2 voltage is blocked by the current from the ECM. Naturally the engine is running rich since it remains in open loop. I'm checking the voltage with the key on and the engine off. I could really use some help here, I'm stumped........
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From: SE NY
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If you are using a scanner to check for closed loop mode you should be able to monitor O2 sensor voltage; in which case it must swing bewteen .9-.3 Vdc.
If it's not moving your O2 sensor may not be getting to operating temp. The ECM supplies a steady .45Vdc to the O2 sensor; the sensor will modulate that voltage once it is at operating temp. So the engine must be running and warmed up before you test O2 sensor voltage.
If it's not moving your O2 sensor may not be getting to operating temp. The ECM supplies a steady .45Vdc to the O2 sensor; the sensor will modulate that voltage once it is at operating temp. So the engine must be running and warmed up before you test O2 sensor voltage.
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From: Crestwood Mo
Originally Posted by 65Z01
If you are using a scanner to check for closed loop mode you should be able to monitor O2 sensor voltage; in which case it must swing bewteen .9-.3 Vdc.
If it's not moving your O2 sensor may not be getting to operating temp. The ECM supplies a steady .45Vdc to the O2 sensor; the sensor will modulate that voltage once it is at operating temp. So the engine must be running and warmed up before you test O2 sensor voltage.
If it's not moving your O2 sensor may not be getting to operating temp. The ECM supplies a steady .45Vdc to the O2 sensor; the sensor will modulate that voltage once it is at operating temp. So the engine must be running and warmed up before you test O2 sensor voltage.
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From: SE NY
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Yes indeed the ECM applies .45 Vdc to the O2 sensor; if measured with a high impedence I've read that you will see around .32 Vdc. So your readings on the cold O2 sensor indicate that the ECM is supplying the proper voltage.
Since you have an Auto Xray scanner just put into Monitor Mode and repeat monitor scans for a few minutes after startup. If after several minutes coolant temp is over 155 deg F and the O2 sensor values are swinging over the normal range the ECM will go into Closed Loop mode.
You can watch the coolant sensor value to see if it matches the dash reading and is comming up to 160deg F. You can also see if the O2 sensor readings eventually begin to swing between say .9-.3 Vdc.
Let us know your observations.
Since you have an Auto Xray scanner just put into Monitor Mode and repeat monitor scans for a few minutes after startup. If after several minutes coolant temp is over 155 deg F and the O2 sensor values are swinging over the normal range the ECM will go into Closed Loop mode.
You can watch the coolant sensor value to see if it matches the dash reading and is comming up to 160deg F. You can also see if the O2 sensor readings eventually begin to swing between say .9-.3 Vdc.
Let us know your observations.
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From: Crestwood Mo
Originally Posted by bradvette
i'll add that "warming up" should be at least 7 mins.
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From: Crestwood Mo
Originally Posted by 65Z01
Yes indeed the ECM applies .45 Vdc to the O2 sensor; if measured with a high impedence I've read that you will see around .32 Vdc. So your readings on the cold O2 sensor indicate that the ECM is supplying the proper voltage.
Since you have an Auto Xray scanner just put into Monitor Mode and repeat monitor scans for a few minutes after startup. If after several minutes coolant temp is over 155 deg F and the O2 sensor values are swinging over the normal range the ECM will go into Closed Loop mode.
You can watch the coolant sensor value to see if it matches the dash reading and is comming up to 160deg F. You can also see if the O2 sensor readings eventually begin to swing between say .9-.3 Vdc.
Let us know your observations.
Since you have an Auto Xray scanner just put into Monitor Mode and repeat monitor scans for a few minutes after startup. If after several minutes coolant temp is over 155 deg F and the O2 sensor values are swinging over the normal range the ECM will go into Closed Loop mode.
You can watch the coolant sensor value to see if it matches the dash reading and is comming up to 160deg F. You can also see if the O2 sensor readings eventually begin to swing between say .9-.3 Vdc.
Let us know your observations.
Racer
Joined: Feb 2002
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From: St. Louis MO
Whew - looks like you're well on the way to victory with this problem. Guess I'm not going to see you standing in the drive with a can of gas and a lighter? What a great bunch of people on this forum - hope to see your Vette back on the street - real soon.
Melting Slicks
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From: OREGON
Originally Posted by 62k
No, but I'll do so this afternoon....Thanks
how did the test go?
at cold it should be at 1K ohms, and when hot it sould be at about 50-70 ohms
if it didn't move off of 1K then theres your problem
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From: OBAMA IS HITLER
Originally Posted by 62k
Even longer....Finally, after about ten minutes or maybe more...I noticed you have a superram intake. Have you had any problems with lean mixtures??????
a different chip tuner completely screwed up my build last year though, didn't touch the main fuel table because he doesn't have a clue......and it ran so lean, hot and detonated with destruction to 2 piston lands.....this tuner's name is jesse azzato (ski_dwn_it)
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From: Crestwood Mo
Originally Posted by bradvette
no, not at all......the tuner made sure of that. its now running great. this tuner is the owner of www.pcmforless.com (see sig).
a different chip tuner completely screwed up my build last year though, didn't touch the main fuel table because he doesn't have a clue......and it ran so lean, hot and detonated with destruction to 2 piston lands.....this tuner's name is jesse azzato (ski_dwn_it)
a different chip tuner completely screwed up my build last year though, didn't touch the main fuel table because he doesn't have a clue......and it ran so lean, hot and detonated with destruction to 2 piston lands.....this tuner's name is jesse azzato (ski_dwn_it)
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From: Crestwood Mo
[QUOTE=crossfire84]how did the test go?
at cold it should be at 1K ohms, and when hot it sould be at about 50-70 ohms
if it didn't move off of 1K then theres your problem[/QUOT
Coolant temperature checked out OK but will keep the info for future ailments. Thanks again for everyone's help...Need to find the vacuum leak and I'll be on my way to the emissions policestation and the keystone testers.....
at cold it should be at 1K ohms, and when hot it sould be at about 50-70 ohms
if it didn't move off of 1K then theres your problem[/QUOT
Coolant temperature checked out OK but will keep the info for future ailments. Thanks again for everyone's help...Need to find the vacuum leak and I'll be on my way to the emissions policestation and the keystone testers.....
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From: Crestwood Mo
Originally Posted by Topload
Whew - looks like you're well on the way to victory with this problem. Guess I'm not going to see you standing in the drive with a can of gas and a lighter? What a great bunch of people on this forum - hope to see your Vette back on the street - real soon.
I agree, great people....Thanks again....