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david craig
david craig, ASE Certified Technician
Category: Nissan
Satisfied Customers: 1834
Experience:  owner/mechanic at 3D Automotive
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2004 Nissan Frontier 2.4L, manual trans. Fuel pump relay

Customer Question

2004 Nissan Frontier 2.4L, manual trans. Fuel pump relay does not get ground from ECU when the ign key is turned to ON (5 secs prime) or to the START position. I have continuity on the wire that runs from the fuel pump relay to ECU.
When the ign key is first turned to the ON position, does the ECU require input from any sensor or component before the ECU initiates the 5 second fuel pump ground?
Submitted: 3 months ago.
Category: Nissan
Customer: replied 3 months ago.
If the ECU does require an input from a sensor or component in order to initiate the 5 second ground to the fuel pump relay. What sensor or component does the input come from and which pin or pins on the ECU does the input enter the ECU?
Expert:  Jay replied 3 months ago.

Hello my name is ***** ***** thank you for your question.

When you turn the key to the ON position, the fuel pump only comes on for 3 seconds. You would need to turn the engine over to properly check it's voltages

The ground is not Ecm controlled, you are correct on that. You should have a constant ground at the Fuel pump.

Expert:  Jay replied 3 months ago.

I take it the truck turns over and doesn't start? Do you know if you have any codes?

Customer: replied 3 months ago.
Jay please read my question again, I am asking about the ground for the fuel pump RELAY not the fuel pump.
Expert:  Jay replied 3 months ago.

The Ground for the fuel pump relay is ECM controlled. That is the White wire with the Red Stripe

Expert:  Jay replied 3 months ago.

But in order to check that, the engine needs to be turning over to see if that signal is being grounded. Turning the key ON it will only ground for like 3 seconds

Customer: replied 3 months ago.
Ok I understand the 3 seconds, my question is, does the ECM require an input from a sensor or component before it initiates the 3 second ground?
Customer: replied 3 months ago.
I have already done the troubleshooting, I KNOW the ECM is not supplying a ground to the fuel pump relay when the key is turned to ON (few seconds prime) or in START. I DO have continuity on the wh/red wire that runs between ECM and fuel pump relay.
I just need a simple answer to my original 2 part question. Thanks.
Expert:  david craig replied 3 months ago.

Hi Im David, If the ECU doesn't respond with a ground, and it is also missing on ECU then perhaps it is not getting the IGN ON signal to the ECU . If the ECU is getting the IGN ON but doesn't respond with a ground for the fuel pump relay then it could only be either a bad ECU ground or the ECU itself. there is no other sensor input it depends on.

Customer: replied 3 months ago.
Perfect you understood my question, thankyou David.
Expert:  david craig replied 3 months ago.

please accept the answer and leave me a 5 star rating if you were satisfied with my assistance. its the only way i get credit for my help. thanks and have a great week.

Expert:  david craig replied 3 months ago.

.