Pretty much everything I know that relates to wiring comes essentially from reading posts written by HAILERS2 and Icemark, etc. When people asked them something related to an electrical issue, which they excelled at, I would copy the necessary wiring diagram and then reread their responses until I understood what in the rats nest they were talking about. Over time, what they said made more and more sense. And in the whole schematic of things, the wiring for these cars is fairly basic as compared to what goes into today's cars.

 

Not very likely at all, but make sure the alternator is locked into place for if it loosened up some it sagging could cause the alternator to snap off the rear of the Thermosensor and also possibly cause the fuse to blow in the first place.

 

You electrical gurus amaze me. It took me 2 days just to sit down, deloom, and label a t2 harness. Probably doesn't help that I can't differentiate between colors too well haha

 

OK Satch, got the new Thermosensor in and the reading dropped at pin 2I to 6.5 volts. This is still higher than the 2 to 3 volts you said I should see.

Here are all the readings now and they are pretty much the same as before except 2I:

2A = 4.9 v
2I = 6.5 v **

3A = 0 v
3C = 11.5 v
3E = 10.5 v
3G = 0 v

So it seems something else is going on. What do I do now?

Thanks again.

 

Make sure the plug to the Thermosensor doesn't have one of its wires pulled back within the plug for starters. If this is absolutely not happening then unplug the Thermosensor and remeasure the voltage at pin 2I w/key to on and see if it changes from the current 6.5 volt reading.

 

Hi Satch, could you clarify this a bit. I'm not quite understanding what you mean by "pulled back within the plug"

Thanks.

 

There are two wires that feed into the plug. Inside the plug the wires make contact w/the Thermosensor. If the wire(s) are pulled back then it doesn't make proper contact w/the Thermosensor. Try pushing on the wires from the back of the plug when it is disconnected and you'll see if they slide or not inside of the plug.

 

Wires seem secure in plug however, the situation reverted to the same reading that I had before putting in the new sensor.

w/key on:

Connector unplugged from sensor: 2I = 0 volts.

Connector plugged into sensor: 2I = 10 to 11 volts. **

 

Satch, it seems like something is shorting in that circuit or I got a bum new sensor. What's the best way to proceed at this point?

 

There's something very fishy going on here. What you should try to do is removing the wire from the ECU plug which is called depinning. You unplug the plug from the ECU and place a very small tool inside the plug from the front of the plug and make it so the wire pulls out from the back of the plug. After you do this place the ECU plug back into the ECU followed by placing a paper clip into the place where the pin 2I wire was and take a voltage reading from the paper clip w.key to on. It should read no higher than the voltage at pin 2A which is 5 volts.

Another thing you can do is unplug the plug from the ECU housing pin 2I and unplug the plug from the Thermosensor. Then turn the meter to ohms and place one end of the meter on the Thermosensor end of the Green/White wire and the other meter lead to the G/W wire at the ECU plug and take an ohm reading w/no key, again, no key in the ignition. It should be low. You're trying to find out what is causing the very irregular voltage reading.

Another thing to do is w/everything hooked up jiggle the wires that are part of the harness that connects to the Thermosensor w/key to on and see if the voltage at pin 2I changes any. You should probably do this first.

Last thing to do is probably a waste of time but it should only take seconds to do and that is place the red meter lead on the water pump housing by the Thermosensor and the black meter lead on the battery negative post and w/key to on take a voltage reading and it should read very close to zero volts.

 

It's the Engine harness.

Noticed smoke and sparks at the point where it bends back towards the rear on the drives side. Unwound that region, there is a broken wire and others have burned off insulation. Parts people at local Mazda don't carry that harness anymore so I'll try re-insulating with electrical tape and fixing breaks.

Problem is at that point there isn't much slack in the harness so it's tough to work on. Is there some connector on that side so I can free that end. I can't see all the places it goes on that side.

 

The two wires for the Thermosensor are part of the Emission harness so not sure if you misidentified the harness you have problems with or what. Also, what is the color of the broken wire and also the other wire colors that have burned off insulation?

 

It's the harness where those two wires connect to the back of the alternator.

After separating the wires apart, 3 are completely broken and 4 have insulation burned off but not broken. The colors as far as I can tell are:

BROKEN: Green/White, Green, Black/White (thick).

LOST INSULATION: Black/White (thin), Medium Brown (thick), White/Black, White.

 

On a non turbo (your type I hope) the two wire plug that feeds into the back of the alternator is part of the Emission harness (on a turbo it is the Engine harness).

Now the G/W wire is "probably" the wire for the Thermosensor. Take your meter and set it continuity and place one meter terminal on the G/W wire at pin 2I while it is unplugged at the ECU and the other meter terminal to the G/W wire you found broken and see if it rings out. If it does then you have proof that the wire is for the Thermosensor. Since the wire is broken you will choose one part to place the meter on and see if it rings out. If it doesn't then move the meter terminal to the other side of the broken wire. Stuff one terminal into the back of the unplugged plug at the ECU that has the G/W wire so you can leave it and take the other meter lead to the engine bay to find which is the other end of the G/W wire that runs to the ECU plug.

 

Yup, the G/W wire shows continuity with pin 2I.

Thanks and will update if still not working after fixing all those wires.

 

Yes, the ohm meter shows continuity with one side of one of the broken G/W wires.

The problem now is that since I have two broken G/W wires, how do I check which of these two other sides goes to the thermosensor wire I found above?

Thanks.

 

Do the same thing previously but do the continuity test by placing one meter terminal on the G/W wire at the Thermosensor and then go through the possibilities at the other end and when you find continuity you'll have it properly narrowed down.

 

What is the path of that G/W wire in the emission harness? I a bit unsure about how it's related to the Thermosensor and the course it takes in this circuit.

 

The wire basically runs straight from the ECU to the sensor w/o any intermediate connectors. The exact path that it takes to get from one end to the other is beyond me.

 

It depends on how your reading the voltage on 2I.

IF the connectors are on the ECU and the connector is on the water thermo sensor, then you back probe the green/white wrie (2I) with a paper clip or such backprobing the green/white wire at the ECU's middle plug.

IF the green/white wire is somehow not not connected to the water thermo sensors two wire plug, then you might very well read 11 or so volts at the green white wire when backprobing the ECU's middle plug.

IF the two wire plug at the water thermos sensor has a pushed back pin that would explain things. Push back pin meand the green/white wire terminal in the water thermos sensor is not mating with the contact in the sensor itself. IF you pull that two wire plug off the water themosensor and look in the harness plug, both terminals should be even with each other. IF one is pushed back the that means the green/white wire (or the other wire) is shoved back in the plug where it can't possibly make contact with the terminal in the sensor itself. Usually that meas a gentle tug on the green/white wire will cause it to come out of the plug. Means that sucker isn't locked in the two wire plug.

If the two wire circuit isn't being made...................then the ECU defaults to a temp reading of 178* F and that in turn means during START the amount of fuel delivered by the injecotors won't be enough to fire up the car on a cold day. IF the air temp is in the 80's or 90's the car would start a little easier than a 50*F day.

A quick shot of starter fluid in the air cleaner would prove something if your having start problems. If you know you have spark and spraying starter fluid (only a one second spray into the air filter works, no more seconds) makes the car start up for a moment...........then dies, that means to me the injectors are not getting fuel from the fuel rail (usually, not always is the case).

 

^Thanks for replying on this foreign board. The original poster found that there were several wires severed within the Emission harness, w/the G/W wire related to the Thermosensor being one of them, so he's in the process of finding and repairing the damage. This all started w/his 40 amp EGI INJ fuse blowing repeatedly.

 

OK, I fixed what I saw in terms of broken wires and burn insulation.

w/key on 2I (plugged) is about 2.6 V and unplugged is 0 V.

There were some changes but no self-sustained start.

I do not need starter fluid to get ignition. However, it's short lived.
Basically, the engine fires up for a second or two then stops and this repeats as long as I keep turning the starter over. It's like something is shutting the engine off after I get it started.

Other pin readings that I took previously w/key on are the same as before and apparently normal.

2A = 4.9
3A = 0
3C = 11.8
3E = 11.5
3G = 0

 

Go to the Circuit Opening Relay which is Yellow and Black. It's located under the dash and just to the right of the steering wheel column. It has two rows of wires, five in total. On the bottom row there are two wires. One is solid Black and the other is Brown. Jumper these two wires together. This is the same thing as jumpering the fuel check connector but it is more direct. It is possible that the fuel switch in your AFM is not acting properly. If this were the case the car would start up but die rather quickly. Doing this jumper will test this possibility. The other possibility is a vacuum leak of substantial size.

 

Hi Satch.

Before I saw this post, I checked one thing I forgot about and that was the B/W and W/B wires to the back of the alternator.

Plugged I'm getting B/W = 11.5, W/B = 1.75
Unplugged I'm getting B/W = 11.5, W/B = 0

Haven't done anything yet on any of this but this is different than before.

I'll do what you suggest next but wanted to check in about this first.

Thanks.

 

W/key to on do your idiots lights generally light light up as they are supposed to when the plug is connected to the alternator. If they don't then check the 7.5 amp Meter fuse.