Ref. voltage sensors wire check

Hi, if I want to check the reference wire sensor is common to two or tree other sensors, can I test it with a ohm test? What I gonna find? Of course, with ignition off!!!
Thank you

Hi Derek, the best idea would probably be to find a wiring diagram for your vehicle, this way you don’t risk leaving a sensor or module plugged in that may get damaged in the process

A wire diagram would helpful to determine if the 5v ref is shared.
Also, if the wires are the same color on each sensor, it's a good indication that they all share the same source.
I suppose you could use an ohm meter it you disconnected two of the sensors in question and placed one lead on each 5v feed. Like you said, key off of course. I've never tried that, but I imagine you'd want to see very little or no resistance.

OBD Rick wrote: Hi Derek, the best idea would probably be to find a wiring diagram for your vehicle, this way you don’t risk leaving a sensor or module plugged in that may get damaged in the process

Good point!
I hadn't considered that.

Also agree with OBD Rick. Use a wiring diagram...

Good night, ok the "problem" is european digrams are a little bit incomplete...they give you colors, but they don t tell you or show you internal connections. Can you trust on colors 100%? In my opinion, no!!!
Tioretically speaking or not , if you have a car with a 3 or 4 dtcs related with with engine sensors and you don t have the wiring diagram. So if you find out and make shore they are related, you are 1/2way
There are many ways to Rome, if you now same of them is much better
Thanks

Sans diagram I will either use a telecom toner set to ring out wires (fancy high-tech method) or use a jumper wire with a known resistor, say 500 ohm, spliced in ( cheap method).

Toners come in analog and digital and I have used them with great success in electrical, networking, and automotive use.

With the Hoopty-Clip® you simply jumper your reference wire to ground and poke around with an ohm meter looking for similar readings. The idea is to change a bias string to a value that sets it apart from the rest. Each sensor has it's own internal resistance but they are typically higher - the lower jumper resistor will limit current (if you need to work live for some reason) and swing the whole chain low enough to tell the bias lines apart. If you get a near zero ohm reading you need to find the pinched wire or shorted sensor.

If the PCM pulls the bias lines to ground with key-off you'll need to disconnect the PCM as toners can't work with a short to ground. If you do that anyway you can forgo the resistor or toner altogether and just jumper the bias line to ground (after checking for shorts). If you make a few jumpers, each with a different value, you can clip one to each bias line and quickly map them out with a test light going by the intensity using the PCM or an external bias voltage supply.

Grouchy

Thanks a lot for your explanation!

I maybe missing something here or not understood the question but what about checking each sensor with a code's wiring, with a test light?

The 5v ref with test light to batt neg and the return path to bat + that way you load the wiring and I find much more reliable then a continuity testing..... all you need is one strand of copper in a otherwise broken or rotten wire to return a positive result!

(I normally use a beef bulb like a headlight bulb/21W for a bit more load) OBVIOUSLY Making sure not to over load the circuit!

(I've never used a tone tester but I imagine the same would be true?)

So i think what Derek is trying to say, is there a way of identifying which sensors share a 5v (or 12v) circuit without a wiring diagram?
I can't really think of one,I can understand the frustration, looking at mitchell diagrams on Paul's videos then going back to my ancient copy of autodata off a CD sucks...

derekoliveira wrote: Good night, ok the "problem" is european digrams are a little bit incomplete...they give you colors, but they don t tell you or show you internal connections. Can you trust on colors 100%? In my opinion, no!!!
Tioretically speaking or not , if you have a car with a 3 or 4 dtcs related with with engine sensors and you don t have the wiring diagram. So if you find out and make shore they are related, you are 1/2way
There are many ways to Rome, if you now same of them is much better
Thanks

Sorry ignore me, I read the bit about the 3 or 4 dtc's and went on a tangent!! DON'T know what brought that on!!

Now you can understand my frustration!? I will try to test the way you guys saying. Do you think with a test light it will work?! There is internal resistors!!!!? Right now I have a lot of work at home but sone I will try same thing :huh:

You can definitely test sensor reference positive and negative with a test light(as discussed #4799), If you have 3 or 4 sensors and all of the 5v ref or the return paths have a common fault they are almost certainly common.

If you worried about doing damage with a test light don't (i've even shorted the 5v ref circuit to ground :whistle: by accident with no ill effects.....but don't try this at home it could go very bad )

I would start with a normal test light that draws 100ma - 250ma, you can connect the multimeter at the same time to measure to voltage drop while the circuit is loaded!(I wouldn't expect the voltage to drop below 4.5v from 5v at this load....probably less )

You could disconnect the ecm and all sensor and then continuity test between one of the know sensors with a fault code at the ecm plug (you would have to disconnect or there could be a chance (small)of a false read via a component in the ecm or sensor) once you've established 5v ref and return path at the ecm plug for that sensor then check for continuity with the other sensors with fault codes to confirm common references wiring......but in my mind that's hard work....as Paul says it's not the next easiest step!!!

If I didn't have a reliable wiring diagram the test light route is how I would tackle it!

I'll try to explain "my dilemma"...Sometimes cars appear to me with dtcs from EGR, DPF, MAP, and samething else!!! And in the end the problem is only in a sensor, which is shorted. Why so many dtcs? Because they have ref. voltage in common...One is sick, others suffer
Thank you for helping me!

it happens all the time for me. I am tiered of working with out wiring digra. its look like walking on a dark night with out light and you have to touch everything ( test all the wires). please let me know if anyone can help me to manage wiring diagrams.