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4 o2 sensors
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jerryo Offline
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Post: #1
Question 4 o2 sensors
Mike I have a 97 silverado that I will be attaching a hydro booster to. I am in the process of connecting the Dual EFIE. My problem is this, The pre and post cat sensors have the same color wires. Can I disconnect the 2 post cat O2 sensors to determine the correct wires for the pre cat sensors without causing a check engine light. I have no way of correcting a check engine light. If not is there another way?? Thanks Jerry
(This post was last modified: 04-28-2008 01:51 PM by jerryo.)
04-28-2008 12:59 PM
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colchiro Offline
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Post: #2
RE: 4 o2 sensors
Disconnecting any of them will cause a CEL, each one a different code.

Rick

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04-28-2008 03:43 PM
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mike Offline
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RE: 4 o2 sensors
Disconnect one of the sensors, and then put a known voltage on the wires that you can read at the other end.

Also, if you have your wiring diagram, you can determine which terminal number on the big ECU wiring harness each one has, and find the correct wires that way (you have to disconnect the wiring harness to do this).

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04-28-2008 04:43 PM
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jerryo Offline
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Post: #4
RE: 4 o2 sensors
jerryo Wrote:Thanks for the response. I do have the wiring diagram but am not familiar with how to determine the numbers of the posts. 19 & 21 are the posts but I don't know how to determine where they are on the plug.??? That would be easier can you help???... Jerry
mike Wrote:Disconnect one of the sensors, and then put a known voltage on the wires that you can read at the other end.

Also, if you have your wiring diagram, you can determine which terminal number on the big ECU wiring harness each one has, and find the correct wires that way (you have to disconnect the wiring harness to do this).
(This post was last modified: 04-28-2008 05:26 PM by jerryo.)
04-28-2008 05:25 PM
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mike Offline
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RE: 4 o2 sensors
Unplug it. You can usually see the wire numbers imprinted on the plug and/or the receptacle. You usually have to unscrew something to get the wiring harness unplugged from the ECU.

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04-28-2008 06:03 PM
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jerryo Offline
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RE: 4 o2 sensors
I had the plug off today but didn't see any markings. I'll work on it more tomorrow, see if I can't figure it out. I'll keep in touch... Thanks
mike Wrote:Unplug it. You can usually see the wire numbers imprinted on the plug and/or the receptacle. You usually have to unscrew something to get the wiring harness unplugged from the ECU.
04-28-2008 06:29 PM
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jerryo Offline
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Post: #7
RE: 4 o2 sensors
I have isolated the 2 O2 sensors before the cat and wired the EFIE to them. I have not powered the EFIE yet but I did start the truck with no CEL. will hook up the booster next and power them all together.. I'll let you know. Jerry
jerryo Wrote:I had the plug off today but didn't see any markings. I'll work on it more tomorrow, see if I can't figure it out. I'll keep in touch... Thanks
mike Wrote:Unplug it. You can usually see the wire numbers imprinted on the plug and/or the receptacle. You usually have to unscrew something to get the wiring harness unplugged from the ECU.
04-29-2008 07:06 AM
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mike Offline
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RE: 4 o2 sensors
When the EFIE is un-powered, or the switch is off, it re-makes the connection between sensor and computer (ie the white and green wires are connected). It is only when the unit is powered up and the switch is on, that the EFIE will modify the signal.

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04-29-2008 08:16 AM
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jerryo Offline
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Post: #9
RE: 4 o2 sensors
I know and thats why no CEL's is a good thing, it appears that the hook up was correct. I will power it up when I have powered the booster but that will be a few days, I am on the road for the next 4 days. I'll tackle it when I get back. I believe the EFIE was the hard part. Thanks again for the feedback it helped alot. Jerry
mike Wrote:When the EFIE is un-powered, or the switch is off, it re-makes the connection between sensor and computer (ie the white and green wires are connected). It is only when the unit is powered up and the switch is on, that the EFIE will modify the signal.
04-29-2008 08:40 AM
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mike Offline
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Post: #10
RE: 4 o2 sensors
Smile

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04-29-2008 08:44 AM
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