Hello to all,
I appreciate your help in advance here.
I currently have this vehicle and it cranks just fine, but won't start.
I used to be able to see the codes on the side of the ECM, but am not getting any codes now.
What pins should I check on this ECM to confirm that it's gettting power?

I currently get no spark to the plugs.
I have already replaced the starter solenoid, distributor (including camshaft position sensor inside, new spark plug wires).
HELP.
thanks again,
Howard

 

There are 2 pins that should have 12 volts on them - pins 49 and 59. The power comes from the fusible links located under the hood.

 

Dennis,
thanks for the info. in addition to pins 49 and 59, I found pin 43 to be powered via ignition switch with 12vdc per my EC.pdf.

do you have a pinout of the ecu harness?
I don't know which pins to test on the harness for 12vdc.
thx
Howard

 

If you have the EC.pdf file, you have the pinout. It is on the bottom of page 142.

Pin 45 is 12 volts when the ignition switch is on.

Pin 43 is not a power source for the ECU, it is a signal to the ECU saying the ignition switch is in the START position.

12 volts can be found at various times on various other pins when the ignition switch is on or the car is running and certain conditions are met. Other pins in this category that are signals and not power are pins 9, 16, 19, 25, 44, 101, 102, 103, 105, 110, 112 and 114.

But here is a blow up of the ECU connector drawing -

 

Dennis,
Nice pict of the connector.
Ok I tested pin 45 and it's giving me 12vdc when I turn on the ignition.

I get nothing on pin pins 49 and 59.
According to a circuit diagram, it looks like the they are fed by a leg/terminal from the ECCS relay and it is fed from a fusible Link.
Where are those located? (under the hood)
Do you have a diagram or picture of those for this 1991?

I saw a youtube where fusible Links are like wired thermistor...they will blow like a fuse.
should we replace fusible links with a real fuse?
I am not sure what amperage those would be.
Thanks again for your help.
Howard

 

Dennis,
I located the ECM relay. it's a 4 terminal relay.
Mine is green with these numbers on it: 2523-c9965 12V, 7g411m

In the picture above it's the green relay on the right.
I located that relay on RockAuto. goes for about $12.00.
any good way to test this relay?

I also tested the terminals that this relay sits in. two of them on one-side are showing 12vdc. So I think the fusible links are good.

thx
Howard

 

Yeah, the fusible links are probably good. A fusible link is a fuse. They are higher amperage than the plug in fuses and have larger connection surfaces because of the higher amperage. Sometimes the connection legs are screwed in to make sure the connection is tight.

Yes, the relay socket will have 2 pins with 12 volts on them. One pin is for the electromagnetic coil that operates the relay and the other is for the power that will be switch on when the relay is energized. Pins 1 & 2 are for the electromagnetic coil and pins 3 & 5 (yes, the 5 is not a mistake) are for the power that will flow through the relay.

You can test a relay but it is easier to just pull another blue (or green) relay from another spot and try it in the ECCS spot. These relays are general purpose and used in a lot of applications.

To test a relay, it is a 2 part process - test the electromagnetic coil and test the power transferring contacts. Remove the relay from the socket - do not try to test it while plugged in. To test the electromagnet coil, use an ohmmeter and check the continuity across pins 1 & 2. I don't know what the actual ohm reading is, but if you really want to know, check another blue relay. Or you can jumper 12 volts to pins 1 & 2. You should hear a faint click when this happens. If not, the electromagnetic coil may be burned out, maybe not and you would want to check the continuity with an ohmmeter.

To check the transfer contacts, you will have to jumper 12 volts to the electromagnetic coil (pins 1 & 2) so that the transfer contacts are closed. Then use and ohmmeter to check continuity across pins 3 & 5. A good relay will indicate a short or maybe 2 - 3 ohms.

 

As for the location of the ECCS relay, it is under the hood in the box next to the battery.

See page 166 in the link below:

http://boredmder.com/FSMs/Nissan/Maxima/1994/EL.pdf

 

props to you DennisMik ! you are very helpful to this community

 

Amen to that.
Thanks for your continued help to all here.
Howard

 

Ok Dennis,
I ordered and received a new relay. it was only $12.00.
I installed it, but did not hear the "click" as if there was no power running through the inductor to close the circuit between pins 3 and 5.
I also tested pins 49 and 59 on the wire harness connector to the ECM and still does not show 12vdc.

NEXT:
I do show pins 2 and 3 to have 12vdc on them.
So I ran the socket-2 with 12vdc to the pin 2 on the relay and then pin 1 directly to the ground side of the battery and heard it click.
I did the same test to the old relay and it "clicked" too.

NEXT:
With the old relay (green), I opened and closed the circuit on the inductor to hear for the click.
AT the same time I ran a continuity check with my 2nd multimeter and get a positive beep for continuity when after I hear the click.
I am deducing that my old relay is good.

NEXT:
On the FUSE BOX under the hood, I jumped the socket pins of 3 and 5 together so that should close the circuit to pins 59 and 49 on the ECM connector.
I am now showing that I am getting power through those pins now.
This whole time I do get power on pin 45 when I engage the ignition switch with the key to the on position and it shows 12vdc as well.

Now I am left with why the circuit for the relay on the fuse block isn't working.
When I test pin 2 to negative terminal to battery it gives me 12vdc.
I am thinking I should get the same when touching pin2 and pin1, but do not.
Do I have an open ground to pin 1?
What's my next step here?

thanks again.
Howard

 

Dennis,
Ok with much reservation, I disassembled the fusible link box 1 and saw that the LEAD 1 of the ECM relay was broken.
All of the other wires are at least 18 gauge, but this wire is about 20-22 gauge and after 30 years of service became brittle and broke in half.

i replaced it with 18 gauge and now it activates the relay to the ECM.

After testing the 12vdc on ECM connector pins 59 and 49, they show good at 12vdc.
I reassembled the connector and the car fired right up.

Unfortunately, I replaced the old distributor and needs an idle adjustment/tune-up.
As long as I give it gas it stays running.

Dennis do you have any instructions on giving this distributor/engine a tune-up and idle adjustment.
I read somewhere that it should idle at 700rpm.
Let me know if you find anything there.

Thanks for your help and Happy New Year!.
Howard

 

When doing a tune up, all adjustments are made when the engine is at operating temperature.
The ignition timing is 15º BTDC with the transmission in neutral.
The idle speed is 750 rpm, +/- 50 rpm.

Here is a checklist for doing all the adjustments. Starts on page 29.
http://boredmder.com/FSMs/Nissan/Maxima/1994/EC.pdf

 

thanks for your help on this vehicle. It's fairly tuned and running smoothly.
thanks,
Howard