Well i spent all day going through the pins on the ecu. The problem i ran into is that every single pin that was supposed to show voltage showed around 12V, and also the right side of the ecu were that screw goes into the little resistor or whatever that is on the side was getting hot. Anyone have any ideas of why. I was thinking that something was wired wrong and none of the power wires were going through a resistor like they should therefore none of the components were seing the right voltage, please help me. Thanks.

 

bump for the midnight shift

 

Was/were all the plugs connected to the ECU when you were doing this?

 

There are quite a few circuits that run on 5 volts in the ECU, but all the outputs are 12volts. What exactly are you asking?

 

say i check pin 2e the afm pin, instead of being 4v like the fsm says it has 12v.

 

what ECU?? Year and model???

 

87 TII n332 i believe. BUT....its in a 89 N/A. I should also state that the car started and ran fine. Then i shut it off pulled it in the garage unplugged the battery and the next day i came out and went to start it and no spark or injectors.

 

All right, are you reading voltage TO GROUND, or are you shoving both probes into the ECU pins?

 

no im reading voltage to both a ground source and then the ground on the ecu.

 

Use the chassis ground, any of the studs sticking up around the ECU will work...Hold on, be back in a bit...

 

Have you checked your EGI fuse in the engine compartment fuse box? Take a good look at it with a flashlight...

Since I'm not actually there to watch you, I'd have to say you're reading the meter wrong, because the ECU is sending 5 volts to some of the sensors (including the AFM), so there ain't no way you're getting back 12v...If you really are, figure out what you did, I think we can solve all the world's energy problems now

 

i know the fuses are good because i went out and bought all new engine and interior fuses. Another thing i noticed is that on the side of the ecu where that resistor or whatever it is is screwed into the chassis of the ecu is getting really hot. That is what brought me to the thought of the ecu getting to many volts to certain pins. So from what i understand the only power being sent TO the ecu is the main and the battery. Every other voltage is being sent out from the ecu. If this is correct then something is wrong because i also took the plugs from the ecu and checked them and was getting a current in the wires without them being plugged into the ecu. Please tell me if my thought is wrong.

 

There are inputs and outputs. Outputs are things that are controlled like Fuel Injectors, ignition coils, or solenoids, while inputs are signals like from the temp sensors, or power steering computer.

 

on the injectors for example. doesnt the ecu send a grounding signal which makes them pulse or does it send a short power signal.

 

The ECU sends a ground to the injectors, yes.

 

so lets keep it simple should i just buy a new ecu or from what i have told you, would it be something else

 

From what you have told us, I'd say you're doing something wrong...But, what the heck, see if you can find a "known good" used ECU & swap it in...If all else fails, you'll have a spare for future troubleshooting

 

It is rare for an ECU to fail unless it has been tampered with or the incorrect tools (cough, Testlight, cough) were used to test things like the BAC while they were still hooked up to the ECU.

I would not buy an ECU without exhausting all other possibilities. Just replacing it is something a Mazda dealer mechanic would do.

What is the issue that you are trying to fix, that you are even messing with the ECU (well alone testing its inputs and outputs incorrectly)?

 

i get not spark or injector pulse at all. Starter works, fuel pump is temporarly hardwired. Also how exactly was i testing the ecu pins incorrectly. I was told to use a MM and test them while plugs were still attached. If this is not correct please let me know so i can go about this the right way.

 

Depending on what you wanted to test, the plugs would need to be disconnected and just power and ground hooked up.

 

If you put your meter on DC VOLTS.......and put the meters negative lead to a good ground like the studs that mount the ECU.........and turn the key to ON.......and leave all the plugs connected to the ECU......and then backprobe the wires by inserting the positive probe in the back of the plug at each wire......one at a time......you should read different voltages.

On the small plug you should see 12v on each injector plug plus two other wires. On the second biggest plug you should read just what the FSM says in the section that deals with the outputs/inputs of the ECU. Some will be approx 5volts, some 12, some a ground. It's in the section called CONTROL UNIT.

I also think somehow you are doing something wrong with the meter. If not.......something other than the ECU is ....weird. Since the car ran successfully several times.....I say your doing something not quite right.

I also think your ENGINE FUSE is kaput. Change it out.

 

went out today and checked over some stuff. (For wayne88....the connector was the solenoid resistor). Anyway the resistor was only showing about 1 ohm and its supposed to show 4 i believe, also i removed the engine fuse and looked at the connectors and one was popped out, so i took the fuse box out and looked for the wire to put back in and there wasnt one. There was just a big black and red wire going to the bottom prong, but no wire going to the top. I couldnt find any loose wires, so is there supposed to be a wire, i would think there would be to complete the circuit, and if anyone knows what color that wire should be that would be great. Thanks.

 

A resistor only having 1 ohm? That's called a wire...Do you mean 1 K-ohm?

I don't quite understand what you're saying- you pulled the cabin fuse box, and the back wiring for the 15A "engine" fuse was missing? Did I get that right?

 

yea but disregard that i just looked up the cover diagram and i was looking at the fuse right below the engine fuse. But could that soleniod resistor not showing the right ohms be a reason for no spark and no pulse

 

If you're talking about reading 1 KILO-ohm (1,000 ohms)when you should be reading 4 KILO-ohms, yeh, that might be it, but if you're talking reading 1 ohm instead of 4 ohms, that ain't gonna do it...