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Roy, import/domestic specialest
Category: Car
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Experience:  ASE master tech for 40 years
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Suzuki Grand Vitara: 2004 Suzuki Grand Vitara 2.5 V6 4X4..

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2004 Suzuki Grand Vitara 2.5 V6 4X4.. fuel pump not working, replaced, no power to fuel pump. sent ecm for rebuild...still no spark, scan tool will not connect to computer ?
Question: Where exactly does the ecm receive power color/ wire connector location... Is it fused outside of fuses boxes.?

good morning my name is XXXXX XXXXX I will assist you today


How did you determine the pcm was bad????


there is a main relay that feeds the fuel pump relay which supplies power to the pump. there are 2 fuses for this feed to the relay. I will attach a wiring diagram for you to review. 1 fuse is underhood and 1 is inside the car. Check all fuses with a test light for power. I would start here before assuming a bad pcm which is unlikely.


does the check engine light work???





Customer: replied 3 years ago.

Determined the pcm was faulty after tqking to dealer and them telling me that all wiring harness's would need to be relpaced at about 7000 bucks.


They could not get a connection from their scan either. So I sent the pcm to Autotec, they said it had water damage and they would rebuild it.


All fuses were checked by dealer and myself, and my Son.


I was a small dealer and Father was a dealer, grew up in a shop and owned one for several years. Two sons now have shops.


Engine check lights as normal when key is turned on..


No spark power..


My question was and is..


what is the color of wire supplying power to pcm, and where is the power coming from. First I believe that the scan tool needs to be able to communicate.. It will not connect, nether will the dealers. ?


(Scan tool's will not connect...neither the dealer or ours, it previously did on the same car. )


Check engine light does not come on, all other lights seem to function normally.




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ok, thats good information.


the power comes from the main fuse box. that where all the powers come from. I will get a wiring diagram for you.


as far as the communication, the dealer may be right with the wiring harness issue. the other thing is one of the other computers may be pulling down the network line. the others need to be disconnected and then try to communicate till you cannot, then you know which computer is having this issue.


why did they say the harness needed to be replaced???



Customer: replied 3 years ago.

OK Thanks


What other computers are we talking about ? Where are they, how do we disconnect ?


The dealer tech was following the line from the pump to the computer, saying He could not get power through, however, He did not check with scan tool until I was there to pick up car. Believe He should have done that first.. as I requested as I could not get a reading from scan tool.. and suspected an pcm failure, and I had no way of checking pcm. (Neither did the dealer) He did say He was receiving negative impulses from the pcm, however I am doubtful that He did. A young sharp fellow that I believe started at the wrong end, and when I asked if He checked the pcm, He said that they normally do not start there ? Perhaps He was right, however, the fuel pump was not the problem, it was replaced, then power ran directly to it... no start... no spark..

ok, there is a body control module, transmission control module and instrument cluster module. they all talk to each other on the same network line. if one goes bad then none will communicate.


a scan tool will not tell you if there is power to the fuel pump. it needs to be checked with a voltmeter and test light.


negative impulses are ground signals which mean it may have power but no ground, that is if he is correct.


the bcm is under the dash, the cluster module is the cluster itself and the tcm can be under the dash or under the hood by the battery



Customer: replied 3 years ago.

So how do we test those ?

How do we identify ?

Will a disconnect tell anything. ?

Will the wiring diagram You are providing show location of each.?

Fuel pump power was not at pump...(test light and multi tester confirmed)


How could it send negative impulses if it has no ground ? He said that the fuel pump relay is power by negative impulses... However... even with power to pump.. no spark.. no run..


How long will You be there today.. I am in Hawaii and it is 740 am now..





I will be here for another 9 hours.


positive voltage is sent to the pump not negative. if there is voltage on the return line or ground, then there is no ground or an incomplete circuit.


you will need a full blown scan tool to check the other modules. a code reader cannot give the needed information


did you check the fuses as I suggested a couple of posts ago??


you can try dis connect but even if it works, nothing is fixed as the issue is still there



Customer: replied 3 years ago.

Thanks Roy


Understand You on the pump power and ground, I was told at the dealer that the fuel pump relay was powered by negative emc impulses ?? Then would send positive to pump which it does not do.


Is this right ?


So let's back up...


Can You provide me with the color and locations of:


1. positive power wire to to operate)


2. negative or grounding wire to ECM ..PMC..Computer(has to have ground..right ? )


3 impulse line to relay and rather it is negative or positive


Back at computer now..


mahalo Roy




ok, I have not found a good picture of the connector for the pcm for power and grounds. thats why I have asked you twice to check the fuses as that is where the power originates for the computer.


there is positive voltage fed to the pump. not negative. I will stand by that as it is a basic principle of electricity for operation of the pump.


there is no impulse line to the relay, just 12 volts that is fed according to the diagram I sent you. one feed is battery or all the time and the other is 12 volts key on.


check the diagram and you will see what I mean



Customer: replied 3 years ago.

Great Roy


So then: How about color and locations of...


1. positive power wire to to operate)




2. negative or grounding wire to ECM ..PMC..Computer(has to have ground..right ? )



Roy I have checked fuses several times.. so have others.





found these 2 diagrams


did you check the fuses yet??????



Customer: replied 3 years ago.

Fuses... yes...several times


Tried moving relays around also..


Nice info however..did not see a power supply for an ecm or pcu ? and are these terminal numbers, how do we relate to wiring from computer ?


Thanks Roy.. I would really like to see a detailed color wiring diagram.


One time I found a fuse between the power supply and the fuse block to the ecm... this was on an older Suzuki. Need to know if ecm is receiving power..?


1. thanks thats new information for the fuses

2. do not move relays as they are different and belong in specific locations

3.powers and grounds are on the diagrams. look closely. look for terminal numbers for the wires and check the colors. I do have a color identifier for this model. looked high and low.

4. if you have a check engine light and a reference voltage to the throttle position sensor then the pcm has the needed powers.

Customer: replied 3 years ago.

OK Roy


So "No" check Engine Light. (It would say .."check Engine" right ?


If the throttle position sensor is the one mounted toward the front of the car .. it gets power when key is on.

Noticed that the ABS light comes on then goes off ..







the check engine light will say that, service engine, a picture of a yellow motor.

tps is on the throttle body by where the big hose from the air filter meets the motor.

abs has no effect. that operation is normal.

if you have no check engine light, you either have a bad fuse or the pcm has in fact failed


Customer: replied 3 years ago.

OK Roy there is no "service engine" or check "engine light" of any color


I am a bit unclear about the tps... there are two electrical connections at the throttle body. Is the TPS the one closest to the intake manifold (that would be the most rear on car.. Or is the TPS the one closest to the airbox.?l





it attach's to the black box on the side of the throttle body.

with no light and you checking all fuses, it is most likely a failed pcm.

Customer: replied 3 years ago.

Roy I will be contacting the rebuilders of the pcm Monday AM as soon as they open.


I still have not been able to locate the power feed to the computer.


The diagrams You provided do not indicate power to pcm that I can see.. Please point it out to me,if I am overlooking it... I can see a ground...But no power point to the pcm ??


Thank You..



second diagram has 3 power sources to the pcm. ignition switch on is the diagram.

Customer: replied 3 years ago.

Thanks Roy


How do I match the diagram up with the plugs ?


I see many numbers on the diagrams, however do not see them on the plugs.?





I will attach a connector diagram Roy

Customer: replied 3 years ago.

OK Roy here is what I did.


checked power on C51-2-3


2-6 & 2-7 fuel injector s 1 & 2

2-18 & 2-19 " 4 &

2-20 & 21 power source

2-27 & 2-28 injectors 6 & 5

E61-8 main relay

All the above read as on diagram.?


all grounds were checked by meter.. all ok


I did not get an "engine trouble light or check engine light at any time.?


You indicated that the diagram You sent me on the wiring would show me the fuel pump... where is it on the diagram..having a bit of trouble spotting it. ?


What now ?





the pcm does not power the pump it only grounds the relay as per the inputs.

the more we look at this the more it looks like a pcm failure

I will look for the ground control

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