Short story of what happened. Tire rubbed through wiring harness on drivers side. As far as I can see " I pulled the harness there apart" the black with yellow stripe wire got damaged and shorted itself out against the shielding wire that is there too. Commander showed -250 with key on. I pulled it all apart and thought I seperated everything. I bought a new 3 bar from the dealer $140 and plug it in, zap. Tested it and it was toast. I did the wiring one more time and hooked up a stock map, key on was getting -20/+10 (good). Okay, thinking I fixed it this time. I bought another one today and, mother f'er ZAP! There go's another one.

How can I go about checking the wiring for the map sensor? I'm trying to look at the wiring diagram in the manual but you know how that gos. Can anyone shed some light on doing a wiring rundown. I guess I just need to do a continuity test on the three wires, right?

Thanks....hopefuly someone can help.

 

... and make sure they don't have continuity with other wires that they shouldn't, or with ground.

What ECU do you have? Perhaps you can just get a GM 3-bar sensor (~$60), since they are almost certainly cheaper than the stock one (>$100?). The stock sensor (if you got yours from a Mazda dealer) is a 2.2-bar sensor, not 3-bar.

-Max

 

I've got a gm 3 bar sensor and pfc. I bought my recent ones from the dealer because I get them so swift.

How do I check to see if they have continuity with other wires? Should any of those 3 wires have continuity with each other?

Thanks for replying mx.

 

^

 

You've pretty much got it figured out. Your tire rubbed through the wiring and shorted the wires, that is where the problem is. Go back and wrap each individual wire= problem solved.

I don't know if the GM sensor has the same plug, if not double check your splices too.

Keep checking...

 

I saw that it happened to you too. I split the loom open and only saw two wires that were rubbed through. When you fixed yours, what did you do about all that shielding? Also, do you still happen to have pictures?

Thanks.

 

I have pictures somewhere but I can't find them right now.

IIRC there were only 2-3 wires with the insulation rubbed through. The shield wire touched the conductor and that was where the short was. It was very subtle, just one strand of shield wire was touching the conductor. I separated the shield wire from the insulation for about an inch and then wrapped the wired individually.

 

What do you mean conductor?

 

Just making sure that your connections are OK

on the GM 3 bar the connections are listed as A,B and C

"A" is Ground and is connected to the GM adapter connector which is connected to the OEM RX7 Black/Grey wire. "A" should show continuity with any ground.

"B" is the Map sensor Volt Out and is connected to the GM adapter connector which is connected to the OEM RX7 Green/Yellow wire.

"C" is 5 Volts in and is connected to the GM adapter connector which is connected to the OEM RX7 Brown/White wire.


I am sure you have it correct, but it never hurts to double check.

 

I'll check again but which of those wires should have power running to it when the key is on?

Should any of those have continuity with each other?

 

With the Map sensor disconnected

No continuity between any combination (A&B, A&C or B&C)

Turn the key to the ON position:

With the COM (ground -) probe of the DVM (set to Volts DC) connected to a good ground,

Touch the + probe to:

"A" Blue/Grey should be a ground only--- 0 volts

"B" Green/Yellow should show 0 volts with the sensor disconnected.

"C" Brown/White should show 5 volts

 

Here is what I found.

This was done with the key on the ON Position.

A has continuity with C and chassis ground.
B has no continuity with anything.
C has continuity with chassis ground.

A shows .03 volt
B shows 4.15 volt
C shows 5.04 volt

When doing continuity tests, does it matter which probe I use?

 

I cut the green/yellow stripe wire from the ecu. Tested with the key off and it was pulling 4 volts. Why would the power fc be throwing out voltage through there? I thought there is supposed to be no voltage from the green/ yellow stripe wire?

I'm confused........

 

Was the MAP sensor connected?

I think some of the circuits actually get constant positive voltage and it is the ground side that gets switched/sensed by the ECU. That might explain why there is positive voltage even with the key off.

-Max

 

Map sensor was no connected. I was testing the map sensor plug. I tested the voltage from the green/ yellow stripe wire right from the ecu with the sensor umplugged.


So, you're saying there is nothing wrong?

 

Took at look at my commander. Looked at my settings and somehow my pfc reset itself. All of my settings are back to stock.

This would cause the bad reading on my commander/ boost screen huh?

 

^

 

^

 

The tests that you did seem incorrect. The PFC simply accepts and interprets the 0-5 Volts from the "B" connection from the MAP. With the sensor removed there should be No voltage at "B". In other words, the only voltage at 'B' should be that which would be generated by the sensor.

 

B is the signal wire (green w/yellow stripe) right? Well, it had voltage coming out from the connector itself and it had voltage coming from the computer side too so I don't see how a short would cause this. Not sure how I could have tested it wrong. The map sensor was disconnected when I did this.

 

not s short technicaly. but the signal wiring must be getting voltage from another hot wire in the harness somewhere. what was the voltage reading? and yea with a 3 bar in there and the pfc not adjusted for it, it will give an odd reading.

 

I cut the signal wire right off the ecu so it wasn't connected to the big harness anymore. I tested the signal wire right from the ecu and it was pulling like 2 volts.

What do think........... I fixed all the damaged wiring so I dunno.

???

 

^

 

OK. Since we seem to be getting nowhere with the 3 bar sensor disconnected.......

Test the output this way but you will need to reinstall and connect the 2 bar stock sensor to test this.



Blue/Light Green should be a ground only--- 0 volts in all conditions at ECU pin "4""D" regardless of key position.

Green/Yellow should show ~2.6 volts with the key in the ON or RUN positions or ~1.5 volts with sensor connector and ~1.5 volts at idle and at ECU pin "1""O"

Brown/White should show 5 volts at the "F" connector of the ECU at pin "3""I" with key in ON or RUN position.


If that is not OK you are going to have the recheck the "Shield Wire" package for a break at either B/LG or G/Y.

 

I'll give her a go.......