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Ram__46

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Hi everyone. I have a doubt. If I have to test a ground pin of a 5V connector (suspect bad ground), to do a continuity test is it necessary to touch with the multimeter probe any point of exposed metal of the chassis? Or do I have to touch exactly and directly the negative pole of the battery?
Is it the same thing?
Thank you for help :)
 
What application is this?
Is the chassis definitely supposed to be connected to 0V?
 
Hi and thanks for your reply, it's a 5V (2 pin) connector of an exhaust gas temp sensor in a car. I suppose I have a bad ground wire, but I can't reach the ground collecting the wires of that sensor (and many other sensors) because it's located under the dashboard (hours of labor to reach it). I read 4.963V between the pins, but the ground pin is at 0.037V with respect to a metallic part in the engine.

Instead, from the other pin of the connector to the same metallic part of the engine I have 5.00V. So the ecu sends perfectly the 5V, but the ground it's not perfectly at zero.

The question is, is the ground wire a bad ground? I'm a novice in electrical repairs :)
For comparing, I checked another EGT sensor connector, and tension at the pins is 4.995V, quite perfectly 5V (I suppose also within the multimeter error sensitivity (it's a cheap multimeter)).
 
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Yes, those very slight differences are to be expected. It may be worth you try to connect a temporary wire from ground to the pin which you know should be grounded.
 
That's what I wanted to do. Create a new ground wire and get it to another ground in the engine bay. If the sensor starts working properly again, I know the answer. But could a bad ground wire give that 0.037V value? I really don't get it :) thank you :)

The other sensor working properly had 4.995V at the connector. So I suppose that at the pins there must be quite exactly 5.00V and not 4.96 or so.
 
Rather than test voltage, what you need to do is a resistance measurement between the ground of the sensor connector, and a known ground. Set your meter to resistance/Ohms.
 
I did it but I don't remember the value. I remember I read around 3.6 kOhm (probably) but it seemed too low to me and strange, I'll repeat the measure. What range of values should I expect?
 
I did it but I don't remember the value. I remember I read around 3.6 kOhm (probably) but it seemed too low to me and strange, I'll repeat the measure. What range of values should I expect?

If the wire should definitely be grounded, then 3.6k is far too high. Depending on meter quality, lead resistance, length of cable etc I would expect around 1 Ohm. Again, don't worry about slight variations.
 
Minutes ago I did the attempt. Cold engine. Diagnosis told 130 °C for that faulty sensor. I grounded it to another ground in the engine bay and I immediately got plausible results: 31°C while other sensors were at 29 °C. I think I found the problem. Now I have to detach wires from the connector but I don't know how to do it properly. Thanks again
 
Minutes ago I did the attempt. Cold engine. Diagnosis told 130 °C for that faulty sensor. I grounded it to another ground in the engine bay and I immediately got plausible results: 31°C while other sensors were at 29 °C. I think I found the problem. Now I have to detach wires from the connector but I don't know how to do it properly. Thanks again

Excellent! Post a photo of the connectors. Maybe we can see how they release.
 
Here are some pics. It seems that the white/yellow part (where wires get into) can be removed pressing that pin. I tried with a screwdriver but even with force it didn't move ?. I have a set of tools to remove wires from connectors, but I never did electrical repairs before :)

If you have ideas I'd be glad and grateful
 

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I think you're right with pressing those side bits in. Maybe something more suitable than a screwdriver though.
 
Perfect. I'll try. But then, how to I detach the wires from that yellow connector?

Mmm, not sure. I think I'd be having a Google search if I were you. Bound to be something on the web.
 
Hi, I'm looking for an eyelet connector to put the new wire to ground. It's scarce in my city (not to be found), especially if I want a quality set. Do you think it's important to put certified connectors or it's enough using cheap chinese ones? I'm no expert about it and I'd like to avoid my car being on fire :) Thank you
 
Hi, I'm looking for an eyelet connector to put the new wire to ground. It's scarce in my city (not to be found), especially if I want a quality set. Do you think it's important to put certified connectors or it's enough using cheap chinese ones? I'm no expert about it and I'd like to avoid my car being on fire :) Thank you

To be honest, as long as it is solid and well crimped I would say you would be fine. Make sure you do a 'tug-test' to make sure the wire is firmly held.

Fire is not an issue in this case as the current is very low, but you don't want a bad connection giving you reliability problems.
 
Thank you a lot. I don't know what a tug-test is but I'll make sure is firmly crimped.

Ah, yes that's a UK term sorry!

Try and pull the wire out of the crimp. It should be virtually impossible.
 

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