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Code 556 & 543

cgbier

Well-Known Member
Joined
September 23, 2013
Messages
226
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City, State
Saipan
Year, Model & Trim Level
94 Mazda Navajo
Engine died while driving. Scanner shows following codes: 556 & 543

Relay is tested and works (putting your finger on it while turning on ignition). The spool has about 80 Ohms.
Pump ain't working.

556: fuel pump relay primary circuit failure
543: fuel pump secondary failure battery to control Module.

Is that a cabling issue?

Where do I find the fuel pump fuse? and that stupid dead man switch?

Any help is highly appric..., abbrec..., aprec..., thanks in advance.
 



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Does anyone have a color scheme for the fuel pump circuit?
 












Did the test with grounding the FP port in the diagnosis plug. Pump didn't work.

Did the continuity fest at the fuel pump connector. Got some 4 Ohm (bit of a wriggely testing lying on the ground, flashlight between the the teeth, one hand holding the fest probes, the other holds the connector, the third hand holds the tester). Does that mean the pump is ok?
 






You must disconnect the wires on the "inertia" (dead man switch) for a couple seconds then reinsert the plug, then press the reset button on top of the inertia switch.

Then disconnect both battery cables for 2 min. to clear the codes.

Now start the engine.

If this doesn't get you going then you will at least begin trouble shooting without unknown open circuits. i.e. the inertia switch.

You can test the inertia switch like any other switch.

0 ohms = closed. which is of course what we want.:)

Hope this get's ya running!
 






I'll try that.

Thanks!
 






That inertia thingie is ok. I get 12V to the connector at the pump.

The pump side still reads 4.3 ohm when I measure the resistance between the two wires on the pump side. Is that normal - meaning means a healthy pump.

What I don't get though, is contunity between terminal ground and body ground. Where the is the ground of the fuel pump connected to the body?

When I connected everything together, I gave it a try. On turning ignition on, there was no sound from the pump. I let the engine crank for a second or two. There was a cough, but it didn't start.

So:
- ground problem?
- pump is ok, but doesn't prime? Why?
- pump dead? Continuity should be 0, but is constant 4.3 Ohm.

Relais, fuse, inertia switch are ok. Haven't tested the PCM yet.
 






oh, and while the engine was cranking, there was a fuel smell from around the tank. Wasn't there before.

I have the feeling I'm getting close, but don't know where to.
 






There's two fuel pump relays?

I've only testet the one in position C so far. What is the other for?
(image from Alldata - I hope that is allowed)
 

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First:

Your diagram is incorrect :( B & D are for ABS, one for the ABS controller and one for the ABS servo.

There is only one fuel pump relay. The map is on underside of power dist. cover,,Missing?,,

4.3 ohms across the pump seems good. 12v / 4.3 ohm = 2.7 amps.:thumbsup:

Ok so the ground... fuel pump ground is the black wire.

Black with white strip is ground for the fuel gauge sender.

Pink with black stripe is pump 12v.

Yellow with white stripe is gauge sender 12v.

Test ground:::: insert one lead of ohm meter to Black wire on chassis side, not the pump pig tail, and ground the other lead to the frame, and then the body, You should get continuity on both. (make a clean bare metal spot on each to insure good contact) You will get some resistance here..long wire.. up to 3 ohms. Three ohms would indicate a poor connection but is likely the test equipment....bad contact at the probes.... were just looking for continuity here.

If you get continuity on only one... your ground strap from frame to body is broke or loose.

If you get continuity on body only... the ground strap from engine to frame is broke or loose. ;)Good news here is if you have ground from black to body the wire is good.

The black wire returns all the way back to the power dist block under hood and is attached to the body near the power block. (some variation from model to model on exact placement, usually in front of the power dist. near the starter relay/solenoid. others are near the OBD link.

Sorry if this sounds a little "preachy, teachy" just try'n to be thorough.:D

P.S. You can also run 12v and ground direct from battery to the pig tail and test pump that way. ONLY RUN IT FOR A SECOND THOUGH..NO AUTOMATIC PRESSURE SHUT DOWN. Don't want to be pop'n fuel lines!

NO need to run 20 feet of wire just grab a battery and slide it under the truck.

Take your time run through it all again and you'll get it, your this // close!
 






Oh,

The gas smell was probably the canister purge...no worries...

If non of the above works, there are still other things to check, fusible link and such.
 






Thank you, FR-425, for that very comprehensive write-up.

I tried to measure ground. No continuity (body too rusty?). What I don't get is, if I get 12V on the harness, why don't I have ground to the body then?
I'm close to eliminate the connector in the back and solder that thing together.

Another - very bad - thought: PCM shot?
 






Oh, as you mentioned the Kanister purge: I also have a 565 - canister purge circuit failure.

That wouldn't shut down the whole Truck, would it?
 






Oh, as you mentioned the Kanister purge: I also have a 565 - canister purge circuit failure.

That wouldn't shut down the whole Truck, would it?

I think your ground is busted. You can tap in a ground at the pig tail and screw it to the body somewhere.

Then connect everything back up and give it whirl.

The 565 won't kill the engine..emissions fail though. I believe it is just the total lose of fuel pressure and lots of KOEO cycles got you the 565.

You need to scratch a bare metal spot to double check the ground first though.

If the PCM was wonky you would get unrelated codes. so far they all make sense.

If you do all the necessary tests and still no joy,,, I'm leaning toward a bad Power distribution block.

Don't fight it..... do the direct power test on the fuel pump.

When all logic fails the simplest solution is usually correct..(fuel pump doesn't work = bad fuel pump) ya know?!

Just say'n maybe we are over complicating the issue.
 






FR-425, thank that you let me pick your brain.

It is the pump. When I put direct power onto it, nothing happens. I hear a slight click from within the tank. Just like it is frozen.

Didn't want it to be the pump, as that means I have to wait roughly 3 weeks for it to get shipped in. Dealer quoted me 700 bucks for the assembly.
 












$700.00!!!!!!!!

Is this Trick with the old Sharpie also gonna work with the connectors on the pump?

http://www.youtube.com/watch?v=hkZRSMGqQ0E

Yes, that's genius.

Fuel lines on yours are the same.

I don't know what you have for parts stores in Saipan but you can do much better on price on line.

For example:
http://www.jcwhitney.com/1991-1994-mazda-navajo/fuel-pump-new/p3039837d1452y1991-1994j1.jcwx

Do the fuel filter while you have it out. Might as well.

Jcwhitney is not the only game in town but whoever you buy from, call their 800 number to be sure you get the right part and to confirm that they have the correct shipping info.

Hope you get back on the road soon. :D

It is not necessary to replace the whole unit. just the bits inside.

you will also need the seals for the tank-to-assembly:
http://www.jcwhitney.com/pn/c2062p1782j2s46.jcwx?filterid=d1452y1994g16

Or you can get the whole assembly.. the spectra one is really cheap. but if you where to break the assembly taking it apart it would be best to have the whole unit.

If you go with the cheapy. it would be best to cut an access panel in the floor so in the future you can swap out the pump without removing the tank.

After this mod is complete fuel pump changes take 30 minutes.

Here's a link to show you how its done.

http://www.explorerforum.com/forums/showthread.php?t=182160

$700.00!!!!!! NO WAY
 






$700.00!!!!!! NO WAY
That's living on a remote tropical island for you. :eek:

On the other hand, this would be a special order. The part will be hand picked by a gorgeous, bikini clad model in the warehouse. While on transfer, it will be rubbed and massaged every hour. USPS will keep it in a golden bin. On arrival, the dealer will gold plate all metal parts, screws will be replaced with titanium ones, crowned with a diamond. Contacts are of platinum, so 700 bucks is pretty cheap.

I ordered a Carter brand unit (fuel gauge is also dead since I have the truck) from Rockauto. It's about 110 bucks shipped.

Thanks again for your help.
 






Nice!

Although It will be handled by hairy knuckle dragers!

Merry Christmas,


Hummm tropical wheel'n..........bikinis'............mud..bikinis'...........bikinis',bikinis'
 



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Got it running again. Codes are cleared - well at least the ones related to the fuel pump - fuel gauge is working.

Drinks are on me!
 






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