MAF Connector Wiring

[1990Q45'r]

To clarify......When they want you to check continuity, they are wanting to verify the wire from the MAF connector to the ECU connector is not broken or damaged somewhere along the length of the wire between the connectors. That needs to be done with both MAF and ECU connectors both removed. With both connectors removed, check W (white) wire of MAF connector to ECU connector #27. There should be continuity. Check (B) Black wire of MAF connector to ECU Connector #26, There should be continuity.With connections back together and ignition key on, check B/W (Black and White) (A in manual) wire of MAF connector to ground, should be battery voltage. To check the ECCS relay..... (remove relay to test) when battery voltage is applied to W/R and GY/R pins (outside pins) the relay will click/operate. With voltage applied, the relay is energized and there should be continuity between the other two terminals W/R and B/W (inside pins.)Hope this helps!

Modified by 1990Q45'r at 10:20 AM 7/28/2006

Modified by 1990Q45'r at 10:21 AM 7/28/2006
Modified by 1990Q45'r at 10:23 AM 7/28/2006

[Amybirds]

Ok, I just checked the wires again on my lunch break and verified that my white wire has continuity with 27, black with 26 and b/w has battery voltage. This is as it should be, correct?

Three questions:

1) Reading the MAF diagram, if the MAF connector is hooked up and I'm standing a the front bumper looking down into the engine compartment, the white wire should be going in on the left (the passenger side) and the b/w wire should be going in on the right (driver's side)? If not, that could be the source of my problem because that's how I did it...

2) If I do have my wiring correct going into the connector (white on pass side, b/w on driver's side), then if I unhook the MAF connector and lift it up about 1" and crouch down and look into the terminal side of the connector where it plugs into the MAF, should the passenger side terminal (which has the white wire going it to it) be A or C? Because it looks to me like it would be A, but then it says A should have battery voltage and we've already determined that b/w should have voltage, not white... So am I lettering ABC wrong or did the FSM do it wrong? (or none of the above if I wired my connector wrong in the first place -- see #1)...

3) How do I physically check the relay with a 12v charge? (spell it out for me- I'm learning this electrical stuff as I go...) Wild guess: do I take a wire, fold it in half, attach the middle to my red battery terminal and hook it up to the ends to w/r and b/w pins? Or is there a smarter way to do this? If I've already tried replacing the relay with no effect do I still need to test it?

Thanks!!!

[elwesso]

it says in the FSM you dont want to check for battery voltage on #1 with the MAF connector plugged in, but the ECU needs to be pluggged in and the key on! You should never have to probe the MAF connector plugged in!!!!!

the MAF connector reads left to right ABC as it is in the diagram... FACING THE TERMINAL SIDE OF THE MAF CONNECTOR, NOT THE HARNESS SIDE!! It should be wired, going left ot right... W, B, BW.. on the terminal side.

I really dont see the need to test the relay... but if you wanted to test the relay, hers an attachment how to do that... The relay at the bottom is the blue relay that is for the ECU (at least i think its that one, regardless its a simple normally open relay)..

Basically you follow the diagram on the top of the relay..... Youll see the normally open and normally closed ones... So if you take your meter and check for continuity, it will be there depending on what happens... To make sure the relay works, lets assume we're working with the normally open relay, you test for continuity between the 2 pins, and applying no voltage, you should have no continuity.. When you apply voltage, the relay should click and then you should ahve continuity...

so on the relay i outlined below, between pins 3 and 5 you should have no continuity.. Apply voltage between pins 1 and 2 and you should have continuity between 3 and 5.....

[Amybirds]

Ok, so if A is white then it should have battery voltage per the FSM and my b/w one (C?) has voltage instead (which is what 1990Q45'r says it should be, and looks to me should be from the wiring diagram)...

Any chance someone can check their car and tell me which should have continuity (W or B/W) and which should have battery voltage? I don't want to assume the manual has it backwards when it's more likely I do instead...

About relays -- thanks for the info/diagram! I'll put testing those off for now as I'm sure there are other things to try.

[elwesso]

A has battery voltage to ground, the far left pinon the MAF connector... I just checked it.....

[Amybirds]

You are wonderful for checking!

So this lack of battery voltage could be a source of my problems then.

Would you mind checking to see if your C terminal has battery voltage? (mine does) Just to see if that's something else that's going wrong?

[elwesso]

I checked B and C to ground wiht the ignition on and i had like .02 volts, something miniscule....

[Amybirds]

Ok, so my tests lead me to believe that I have my white and my B/W wires mixed up, but I know that I have white in A (toward the passenger side of the car) and b/w in C so that should be correct. The only thing I see that they both have in common are in the ECU...

Here are my thoughts -- please correct me if I'm wrong.

How does the b/w wire have continuity with pin 27? (or should it? the FSM says so, but it doesn't make sense from the wiring diagram...)

On another note, according to the wiring diagrams, the only way I can see termnal A getting voltage is if the ECU gives it voltage since the white wire doesn't seem connected to the battery anywhere. And the b/w wire seems to connect all the relays that are clicking on my car. If I damaged the ecu when we cut the MAF wires, could it have caused the ecu to send the 12V power to the b/w wire instead of the white wire, and would that cause all the relays to constantly click on and off (by having 12v power when it should have little to none)?

[1990Q45'r]

White wire (A) ( outside towards fender) at the MAF and ECU harness pin#27 should show continuity. Make sure to check at the ECU harness connector not the ECU!Black wire (B) (center) and ECU harness pin#26 should show continuity.Black and White wire (C) (inside closest to engine) at the MAF should be battery voltage with everthing hooked up key on.MAF does use battery voltage, I am guesssing to heat sensor wire.Black and white wire gets power from (M90) ECCS relay. The relay gets power using W/R wire to 25A fuse located in relay box. The 25A fuse gets power using B/Y wire to 100A fuse link.Shorting out something else (what ever smoked) may be the cause of the relays clicking.

Edit: Proper location of wires in MAF harness.
Modified by 1990Q45'r at 9:44 AM 7/30/2006

[Amybirds]

Thanks 1990Q45'r. The thing is that the FSM says "a" should have battery voltage and "c" should have continuity not the other way around as you suggest. The abc that I'm talking about is not the ABC in the wiring diagram of Elwesso's earlier post, (which actually is just referring to diagrams labeled A, B & C on the next page) but an "abc" IN the diagrams on page EG&EC-87 of the FSM.

---

I'll try to attach a picture of my harness freshly pulled off and labeled with how I have it wired... First thing to establish is: is it wired right? If so, is the left (white wired) terminal "a" or is the right (B/w wired) terminal "a" with the harness in this orientation?

Elwesso, is your A (the one with power) the terminal that your white wire or the B/W comes out from on the other side?

If I have it wired correctly, and labeled abc correctly, then I can rule that out as a possible issue.

[Amybirds]

Maybe I'm crazy, but it looks to me like my MAF connector attaches on upside down from how all the diagrams show it should. Here's an illustration from page EG&EC217 along with pics of mine. Should the orientation pins be on the bottom when connected or on the top?
Modified by Amybirds at 9:35 PM 8/28/2006

[1990Q45'r]

I just had to replace the connector to my MAF. Undid the shrink wrap to verify wire locations.White is on the outside. towards fender.Black in midde.Black and White on inside closest to engine.

[Amybirds]

1990Q45'r -- thank you for the clarification. :-) A is the white wire and goes towards the fender. C is the b/w wire and goes towards the engine.

Also, when your MAF is connected, the two alignment pins on your connectors are facing down, correct? If so, it sounds like I have the MAF connector wired backwards, which is good to know.

Now if I can just figure out what we damaged when we connected the three wires with the wire cutters and caused sparks and arcing... then I'd know why the relays are all clicking...

[1990Q45'r]

Amybirds,The connector goes in the way you have it but, it appears the White and the Blk/W are reversed.Is the relay clicking with the MAF connector disconnected and key on ?

[Amybirds]

From what 1990q45r says, I'm pretty sure I have my W & B/W wires mixed up on the terminals so I'll fix that. Perhaps I'll update the pic too to reveal the correct colored wires with the correctly lettered terminals (thanks Wes!).

In the meantime, I've played more with the relays clicking, checking voltage on the wires going to them with the key out and turned to on and here is what I found:

ECCS relay: both W/R wires have battery voltage (ignition on or off)B/W wire has around .7volts withe the ignition off and battery voltage with the key turned to "on".GY/R has battery voltage wiht ignition off and then goes down to 1.2 with the key turned to "on".

Ignition Coil Relay: B/W and BR/Y have no voltage with ignition off and go to battery voltage with key turned to "on"W/B has battery voltage with ignition off or onGY/R has battery voltage with ignition off and 1.2 with key turned to "on".

Haven't yet figured out what all this means, if anything, but any insights or thoughts or new directions to try would be great. Thanks!


Modified by Amybirds at 5:10 PM 7/31/2006

[Amybirds]

I've been spending a lot of time reading the FSM hoping to stumble across some information to help me know why my car is not starting and why my relays are all clicking... I thought maybe something was shorted out or damaged in the wiring or harnesses somewhere, but the only thing all the mis-working components seem to have related is the ECU (from poring over the wiring digrams and hanging on every word in the FSM)...

Here's what's going wrong:

-MAF -- this is what started it all -- we had the harness disconnected and clipped all three wires at the same time with the key turned to ON, which caused sparks to fly and arcing to occur where we cut the wires, along with rapid clicking from the ECRC solenoid valve, the ECCS relay & ignition coil relay and a blown fuse for the ENGINE CONT.

-fuel pump: the fuel pump sounds to come on and pump fuel and keep pumping fuel until you turn the key off. I don't think this is normal: (per EC-25 in the FSM) its supposed to be activated by the ECU for 5 seconds after turning key to on and then go off if car is not started. (note: The fuel pump relay is not clicking like the other relays though.)Along these lines, the voltage on pins 6 & 19 (fuel pump voltage control)on the ECU are supposed to go from 1.9 to zero after 5 seconds of having the ignition on and they stay 1.9. And pin 18 (fuel pump relay) is supposed to go from .8 to battery voltage after 5 seconds and its stays 0.8. So the ECU is clearly not doing something right there...

-ECCS relay: clicks repeatedly when the key is turned to on. I've checked the voltage & continuity between it and the ECU and they are fine so it doesn't seem to be a wiring issue, and the power wire going to it has continuity as well.

-Ignition Control relay: clicks repeatedly when the key is turned to on. I've checked the voltage & continuity between it and the ECU and they are fine so it doesn't seem to be a wiring issue, and the power wire going to it has continuity as well.

-EGRC solonoid valve: clicks repeatedly when the key is turned to on. I have not tested any of these connections because I can't figure out how to get the plastic housing/cover off without disconnecting a zillion things, but from what I read in the FSM, the valve shouldn't be activated unless the engine is on...

Does anyone else know of anything these things have in common that I could be missing?

[1990Q45'r]

If you can't get the ECU to flash codes and with all the other problems, you may need to try a different ECU.

[96Qowner]

A 1994 ECU just became available from a car being parted out.

zerothread/189572

Might have fried yours.

[Amybirds]

Thanks for the suggestions & link. I'm working on getting an ECU.

[Amybirds]

96OWNER:

I saw your post on the other thread and I thought I have a standard 94 Q45, not a Q45t, but how do I know? And how do I know if it's CA or Fed? I tried searching for this info without much luck.

Thanks!

[Gerardjg]

I have this ECU

Part Number A18-B11 P73

Nissan Part Number 23710-71U02

I know it is from a Q 1994 or 95 not sure, If Wes or some one can look up the part number to see if it will work for you, if so Pay the shipping and you can try it for troubleshooting purposes.

[email protected]

[96Qowner]

Yeah, we could use Wes's help on this one. The simplest thing to do is to get the numbers off your own ECU and post them here.

[Amybirds]

Thanks everyone!

Mine is A18 B20 P94 and has a big 4J label on it. I tried searching posts about the ECU part #s and all the lists that I've found only go up to 1993 models, and don't list mine...

Also, it looks like mine would be a CA emissions vehicle as there's a label under the hood that says it meets CA emissions standards. Does that mean I need a CA ECU?

I'm going to search some more to see if I can find out what ECUs I can use and I very well may take you up on your troubleshooting offer Gerardjg (thank you!).

-Amy


Modified by Amybirds at 12:28 PM 8/4/2006

[Gerardjg]

Here is a PDF I found with 14 pages of Nissan ECUs pn model + yearsThe one I have is a 93

NISSAN / INFINITI ECU CORE IDENTIFICATION LISThttp://www.jimwolftechnology.c...D.PDF

I did not see yours on the list

[Q45tech]

All this shows what untrained owners, shadetrees, and ill trained mechanics can accomplish with some effort.

The important fact members should take away it this is not unusal and happens with all makes and models...........we see a tremendous amount of self inflicted damage.

It is getting worse with new G35 young owners [frequently given the car] trash them with mods installed improperly.

[96Qowner]

Bump for ECU info from Wes or Robert.

[elwesso]

Thanks for bumping this 96Q...

Anyway, you dont need a CA ECU.. the car will run fine! Only thing you need to worry about is tcs/non TCS... if you have TCS you need TCS ECU, if you dont have TCS then it doesnt matter.....

[Amybirds]

Thanks 96QOwner for the bump and Wes for the reply. I've ordered an ECU (thanks PopPop!) and am keeping my fingers crossed this will miraculously solve all my problems. I'll keep you posted.

[Amybirds]

Good news & not so good...

The new ECU fixed my weird electrical issues -- no more clicking relays, no more ever-pumping fuel pump! BUT, the car still won't start...

The ECU gives me the following codes: 11 (Camshaft Position Sensor, aka "Crank Angle Sensor")46 (Secondary Throttle Position Sensor, aka Secondary Throttle Sensor)54 (A/T Control Unit, aka "signal circuit from A/T control unit to ECU")

I'll do the Crank Angle Sensor FSM diagnosis hopefully tomorrow, but what is the A/T control unit? I've searched the forum with no luck. The diagram in the FSM puts it about where I'd guess the TCU to be, but I don't have a TCS car, so I shouldn't have one, right? I don't want to pull the car apart looking for a part I shouldn't have...Same with the Secondary Throttle Sensor -- I can't seem to find one per the diagram in the FSM, and I don't have a TCS car, so can I safely ignore this code??

Thanks,Amy

[Q45tech]

YOU HAVE INSTALLED THE WRONG ECU ON YOUR CAR!!!!!!!!!!!!!!!!!!!!!

The ecu expects certain different signals associated with a TCS car...........

GET THE CORRECT ECU BEFORE DOING ANYTHING ELSE!!!!!!!!!!!!!!!!!!!!!!!!

OTHERWISE YOU MAY DESTROY some other subsystem looking for some imaginary fault