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Jerry
Jerry, Master Mechanic
Category: Dodge
Satisfied Customers: 1740
Experience:  ASE Master tech, 30 years exp. troubleshooter, driveability tech
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I have 2002 dodge ram 1500 4.7 I change spark plugs coils

Customer Question

I have 2002 dodge ram 1500 4.7 I change spark plugs coils injectors and new rebuilt
ecu and still missing injector num2 well injector lose pulsation and the other still working
Submitted: 1 year ago.
Category: Dodge
Expert:  camerontech replied 1 year ago.

Hi there,

Im cam and ill try my best to help you out.

HAve you checked the injector wiring for that cylinder? what is cutting out?

1. is it the 12v feed that is cutting out or is the ground from the pcm driver that is cutting out.

IF its the 12v injector feed that is cutting out on that cyclnder than you will have to chase that wire to where the masster splice is and see if it is coming lose.

2. If it is the ground pulse from the driver that is cutting out than a resistance test is needed from the injecttor connector to the pcm.

There could be a chaffed wire somwhere or even at the pcm terminal itself.

There should be "0" ohms of resistance.

You can even run a jumper wire right ffrom the back of the pcm to the injector and see if the pulse restores, if it does than we know its wiring on that side.

Please let me know if you need a wiring diagram for the injector circuit and id be happy to upload it for you!

cam

Customer: replied 1 year ago.
I jump the cable behind the ecu and still do the same
Customer: replied 1 year ago.
I not check the ecu plug yet but is rare only work like 20 second and shut offthe power how check the 12 v and he injector
Customer: replied 1 year ago.
plz sent me the wiring diagram I will work and the truck tomorrow when back from my job
Customer: replied 1 year ago.
i don't know how check the 12 volts
Expert:  camerontech replied 1 year ago.

im going to send you the wiring diagram for the circuit.

you will still need to see which part of the circuit is cutting out, the 12v or the ground pulse.

to do this , you can just use a test light.

start with checking the power feed first.

attach a test light how you normally would and either backprobe the injector or give a little slice in the wire sheithing before the connector (just remember to seal it up with tape after) at the power side.

start the truck... the light should stay lit all the time, if it starts missing and the light is still lit than the 12v feed is ok.

to do the ground pulse check,

test light connector at the 12v batter this time instead of ground and backprobe the negative side.

start the truck.... it should flash.

when it starts missing, see if the flash is cutting out too.

this is the big part, whether or not its the ground pusle or the 12 v

i will upload the wiring diagram in a couple mins,

let me pull it up for you

Expert:  camerontech replied 1 year ago.

here is the circuit.

let me know what you find!

cam

Customer: replied 1 year ago.
the ecu send 12v o is only ground
Expert:  camerontech replied 1 year ago.

oops im sorry, there is more diagrams. it only sent one . give me a sec

thanks

Expert:  camerontech replied 1 year ago.

no the asd (auto shutdown relay) powers the injectors. there will be a couple of splices along the harness.

but you only need to check this if it is losing the power.

it is best to print off the diagrams

Expert:  camerontech replied 1 year ago.

only the pcm give individual ground pulse from internal pcm driver, power is from relay

Customer: replied 1 year ago.
what do you think about cutting the wire behind the ecu and running it straight to the injector and
check the pulsation bcz i always loose the ground pulse
Expert:  camerontech replied 1 year ago.

as long as you can reatach the wire without damaging the connector it is ok.

this will eliminate a wiring issue,

IF you have a low amp probe with a scope you can scope the injector pattern as well. a typical injector draw is 1 amp.

make sure that the pin connector to the ecm is good too, no loose connector or connecton or corrosion

Customer: replied 1 year ago.
thats why the driver ecu shut down right?
bcz the wire maybe have issues
Customer: replied 1 year ago.
I will check tomorrow I let you know
Expert:  camerontech replied 1 year ago.

generally the ecu driver will shut down if overheated by either bad injector or wiring or bad ecu

Customer: replied 1 year ago.
well I replace the ecu twice I believe the ecu is not the problem right
Expert:  camerontech replied 1 year ago.

ok, i though you did that too.

wiring will be the next to verify

Customer: replied 1 year ago.
ok boss I will check the wiring tomorrow
I let you know
Expert:  camerontech replied 1 year ago.

k