WARNING: ERROR IN WD21 FSM

[Tungsten]

After looking at some diagrams and testing procedures for the Mass Air Flow Sensor I have found an error in the FSM for the WD21.

 

Here is the sensor:

 

 

From the MAF sensor side, the layout is as follows:

 

A pin = Reference voltage circuit, +12v or battery voltage to power the sensor (B/W wire on factory harness, goes to ECCS relay)

B pin = Reference ground circuit (B wire on factory harness, goes to pin 17 on ECU)

C pin = Input signal circuit (W wire on factory harness, goes to pin 16 on ECU)

 

If you compare EC-84 with EC-133 the information does not match because C is the signal pin and not A.

 

 

 

Note that they have not swapped the letters but flipped the view of the connector! The connector is in the correct orientation but the letters do not correspond to the other diagram. While the view of the connector is still correct, the wrong/new labels are very misleading.

 

 

Now if you look at the shape of the connector and how it plugs in this makes more sense:

 

 

Here is what they mean by each graphic (note, I fixed the second one to match):

 

 

 

You can also see how the 2 important pin terminals that go to the ECU are gold plated.

Edited September 24, 2011 by Tungsten

[5523Pathfinder]

I think you may be interperting the manual incorrectly. This is one of the times Nissan manuals are a bit tricky. Because they use a, b, c to identify the pins, they dont always switch it depending on how you are performing the test. In the first diagram, you are testing the continuity of the harness between the MAF and the ECM. Both are disconnected and you are testing it looking at the pins of the connector(know as Terminal side), not the wires.

 

In the MAF test, you are testing the output(input to ECM) of the MAF. The connector is plugged in and you are testing at the wires, or the Harness side. Basicly, you have flipped the connector and now a is where c was. It usually is always stated a, b, c, d, for testing purposes(though, I think I have seen it backwards at some point).

Edited September 23, 2011 by 5523Pathfinder

[Tungsten]

They are labeled as A B C on the sensor.

Edited September 23, 2011 by Tungsten

[Tungsten]

I think you may be interperting the manual incorrectly. This is one of the times Nissan manuals are a bit tricky. Because they use a, b, c to identify the pins, they dont always switch it depending on how you are performing the test. In the first diagram, you are testing the continuity of the harness between the MAF and the ECM. Both are disconnected and you are testing it looking at the pins of the connector(know as Terminal side), not the wires.

 

In the MAF test, you are testing the output(input to ECM) of the MAF. The connector is plugged in and you are testing at the wires, or the Harness side. Basicly, you have flipped the connector and now a is where c was. It usually is always stated a, b, c, d, for testing purposes(though, I think I have seen it backwards at some point).

 

Possibly but that's just a layer of confusion then. At least they could have said c b a instead of a b c in the second diagram. Labeling both as a b c makes no sense what so ever. Also, you are testing for voltage in part A in the first diagram and THEN continuity in the following parts.

Edited September 24, 2011 by Tungsten

[5523Pathfinder]

no manual is perfect. It helps knowing what you are testing, and are used to the manuals.

[Tungsten]

Yes but this manual will lead people to testing the wrong thing. It's psychologically misleading because how do you know what's A and what's C?

 

Now if you look at the shape of the connector and how it plugs in this makes more sense:

 

 

Here is what they mean by each graphic (note, I fixed the second one to match):

 

 

Edited September 23, 2011 by Tungsten

[sewebster]

I believe the HS means harness side. I think there is something at the very start of the FSM to explain the symbols.

[Tungsten]

It's retarded, they clearly ask you to unplug and test the harness at the connector. Then they ask you to pull the boot and probe with the connector plugged into the MAF sensor. That's ok though, old Toyota manuals are even worse than this.

Edited September 23, 2011 by Tungsten

[adamzan]

so there really isn't an error lol

[Tungsten]

it's kind of an error because they didn't flip the terminal label around but you can see why they could get away with it

[adamzan]

mods delete plz

[Tungsten]

nice trolling

[silverton]

It's a ginormous tecnical book, there are going to be some typo's/innaccuracies. WD21's are old though, so it doesn't really matter, you're just getting your feathers ruffled for no reason. This post may end up helping something in the future, kudos.

 

There is a typo in my 1988 200SX FSM as well. They indicate the constant front spring rate for the VG model is 116 lb/in. Converting the other two figures they provide, brings it out to 166 lb/in. I cried for a minute, and moved on. BFD! Srsly.

[Tungsten]

If it was something like that then I don't mind but getting a confusing bit of info on a very critical ECU component is worth posting about.

Like you said, I hope this helps everyone else trying to figure out what's going on. The letters are MELTED into the sensor so there should be no reason why those connections should not match. It was definitely a typo on their part.

 

Whoever -1ed this can go die in a hole.

Edited September 24, 2011 by Tungsten