Correct me if I am wrong. The signal return wire only is grounded when the ke is "on"? With Key "off", should I be able to get an Ohm reading from say TPS ground back to the battery? And if it is only grounded with the Key "on", how can I check the quality of the ground of this SGNRTN wire since it will have return voltage on it with the key "on". I would like to check the SGNRTN wire to insure its integrity since so many sensors use this wire.
SGNRTN Wire question:
- Thread starter FoMoCo17
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Three50won
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- Jul 11, 2010
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FoMoCo17...on the TPS (if that's what you're talking about) the key has to be on. One wire gets the positive and the other gets the negative...or you can put the negative wire (on the voltmeter) to a good ground source. And make sure you have the correct setting on your meter.
The signal ground is connected to battery ground all the time. Pin 46 connects to pins 40 & 60 inside the computer. Pins 40 & 60 connect to two black wires that connect to one black wire with a quick disconnect. The other part of the quick disconnect is wired to the negative battery cable and grounds to a bolt near the windshield washer filler.
Computer internal circuitry:
You may want to copy the diagram to your PC and view it with windows Picture & Fax viewer. That way you can enlarge it to see the fine detail.
The battery common ground is a 10 gauge pigtail with the computer ground attached to it.
Picture courtesy timewarped1972
Correct negative battery ground cable.
3.) The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to its proximity to the battery, it may become corroded by acid fumes from the battery.
In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
You'll find it up next to the starter solenoid where the wire goes into the wiring harness.
Computer internal circuitry:
You may want to copy the diagram to your PC and view it with windows Picture & Fax viewer. That way you can enlarge it to see the fine detail.
The battery common ground is a 10 gauge pigtail with the computer ground attached to it.
Picture courtesy timewarped1972
Correct negative battery ground cable.
3.) The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to its proximity to the battery, it may become corroded by acid fumes from the battery.
In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
You'll find it up next to the starter solenoid where the wire goes into the wiring harness.
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I shall have to check again ... but I am sure that when I put my ohmeter on the SIGRTN wire and the battery "Negative" terminal I was showing no continuity between the two. So, your saying they are grounded internally all of the time and I should show low resistence while measuring???
I was under the impression the computer was just monitoring the SIGRTN wire but that it was not actually being grounded. Possibly, I need to look very close at this again tomorrow. Not sure I am gointo be able to interpret everyhting on this schematic but I'll have a look-see ...
I was under the impression the computer was just monitoring the SIGRTN wire but that it was not actually being grounded. Possibly, I need to look very close at this again tomorrow. Not sure I am gointo be able to interpret everyhting on this schematic but I'll have a look-see ...
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