No fuel pump relay activation

Doug Owner/Technician California Posted   Latest  
Resolved
Electrical
2003 Toyota Tundra SR5 4.7L (2UZ-FE) 5-spd (R150)
Crack No Start

Greetings Techs. Forgive me if I have a hard time explaining this correctly, it took me a while to understand what the electrical fault possibly might be…

This Toyota has no fuel pump operation while cranking. I verified that the fuel pump does work by manually activating the C/Open Relay with the AES Wave Uactivate tool. The relay itself is okay but it's not being activated properly, I assume by the computer's fuel control, (FC) connection through the H5 circuit Yellow wire to pin 1 of the relay. Therefore not activating the fuel pump relay. 

Has anyone come across a similar issue to help lead me in a direction on what to test next. When I get back to the vehicle I'm going to test at the ECU circuit E3 pin 10, that should be grounding the relay on the yellow wire.

One thing I did find which was odd is when turning the ignition switch on or cranking the control circuit of the relay wasn't being activated. Only when I switched the ignition off, for half a second did it show power through the control. Not when I turned it on but when I turned it off, from on. This showed up through the connection of the Uactivate tool. I hope that made some sense! 

Once again I apologize for any confusion but it's taking me hours just to research the wiring diagram and try to figure out what is actually happening at the vehicle, and then another hour or so to write this up. :-)

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Michael Technician
Indiana
Michael
   

Doug, I had one similar to this one time. Mine turned out to be a bad under hood fuse box. I used a couple add a circuthe pump issue also​.​it fuse leads to re-establish power to the offending circuit. It was either the connection where the fuse plugged in or a break on the circuit under the plastic, can't remember. I believe mine had the issue with the “EFI 1” 15 amp fuse, in turn causing no…

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Greg Instructor
Ireland
Greg
 

I have come across a case before where there was a botched wiring repair. The tech tried to replace the wire to terminal 86 (coil positiive) of the fuel pump relay by joining into a 12v supply to another circuit. The other circuit, by design, only supplied 12v during ignition and cranking….not running. The car started and then stalled, continuously. You might have a bad repair, or a wire may be…

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Doug Owner/Technician
California
Doug
   

Yes that's exactly what it's doing it starts for a few seconds and then cuts out. But that I assume was being caused by the temporary activation of the pump that I heard and saw through the switch activation. Thanks Greg.

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Jordan Apprentice
Ontario
Jordan
 

Hi there. Not sure if it applies. But we had a tacoma that would start then die. It was the fuel pump resistor.. would allow current then heat up and open... I don’t remember where it was another techs job. But just throwing it out there.

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Grant Technician
Illinois
Grant
   

The DTC chart for P0230 Fuel Pump Primary circuit …has a good wiring diagram. The C/O relay will be grounded by the ECM briefly when initially turning key to crank. However, that is very brief. As the CKP generates voltage, the ECM will simultaneously release that C/O Relay ground and provide ground for the Fuel Pump Relay.

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Doug Owner/Technician
California
Doug
 

Hi Grant thank you. Yeah that's what's odd about the instantaneous activation that I see while turning the ignition switch off, not on. And I'm hoping but I have a feeling that it's going to be difficult to find the culprit. Hoping it's just the ignition switch….

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Tony Owner/Technician
Missouri
Tony
 

That is not how it works. The C/O relay stays on as long as the PCM a sees RPM signal by grounding that relay's coil using the FC circuit. The FP relay switches between full and reduced power modes.

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Grant Technician
Illinois
Grant
 

I stand corrected.

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Glenn Owner/Technician
Texas
Glenn
 

Hello Doug, I have chased a few different makes and models for this issue and usually ends up being the most common part that sees the most use and that would be the ignition switch. Verify the powers in and out of the ignition switch during cranking.

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Brian Technician
New Jersey
Brian
 

I am off from work today so I can’t look up the info for that year but see if there is a fuel pump resistor under the hood mounted near passenger fender area - small silver box with ribs. i know the 2006 has one and there are wires going to it. If there check resistance but sometime things will read normal and then fail when powered up. Good luck.

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Doug Owner/Technician
California
Doug
 

Thank you Brian I will check that when I get back. As well as the ignition switch and computer connection.

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Tony Owner/Technician
Missouri
Tony
 

Driver's side fender.

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Jon Owner/Technician
California
Jon
 

I would look at the ignition switch

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Timothy Owner/Technician
Wisconsin
Timothy
 

I could never really understand why Toyo always had this weird set-up, with essentially two fuel pump relays: a relay to supply power to the relay that runs the pump?! If there's no ground being supplied to the circuit as you state, then the PCM has failed, or it's not seeing crank or it's in theft. Theft disable, usually means a no crank, but not always. If you've only got this issue, and all…

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Doug Owner/Technician
California
Doug Update
 

Thank you gentlemen for your responses. When I get back to the vehicle I have some work to do and I hope I don't spend another half a day chasing my tail. But that's the way it is, one step at a time starting with the simplest. I will reply with what I find. Thank you, doug!

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Jesse Owner/Technician
Georgia
Jesse
 

This sounds like an anti theft concern. Have you checked for the theft light with bulb check? See if the customer has another key to try before extensive testing.

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Jordan Apprentice
Ontario
Jordan
   

That’s good info, thank you! The Tacoma we were working on. Had similar symptoms Start then die. But my boss said to check for a “start signal/authorization on the scan tool” I thought it was theft as well! and it was allowing a start. Authorization said OK. I guess in the sense of BMWs for instance looking at the CAS module to see if it recognizes keys.. So we replaced the pump. Still same…

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Doug Owner/Technician
California
Doug
 

Thank you Jordan. I think they do and that's one thing that I missed yesterday that I'm going to check today on my scan tool. And hopefully it's just a resistor. This system is way more complicated than it needs to be! Just like Hondas LOL.

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Michael Technician
Indiana
Michael
 

they all have a pid for that, everyone calls it something else. You always have to scan through looking for security type pids in the immobilizer data. unless you are lucky and only work on one carline.

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Doug Owner/Technician
California
Doug Update
   

And if I have to replace that fuel pump resistor some of my only options are through eBay. Does anybody have a listing otherwise to purchase one if I need to? And if I have to temporarily bypass the resistor I assume that would be okay. It's operation is for different engine loads and higher or lower fuel pump operation, correct? Thank you, Doug

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Tony Owner/Technician
Missouri
Tony
 

Toyota dealers sell Toyota parts. … It is bolted to the left fender ahead of the main relay/fuse box and looks like this: diag​.​net/file/f3chsu987… Note: There's another similar looking resistor assembly near it if you have DRLs.

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Tony Owner/Technician
Missouri
Tony
 

Since it starts and dies, and based on your observations, you have an open FP resistor or circuit. Look carefully at the Fuel Pump Relay in the EWD. It is NORMALLY CLOSED. The FP relay is there to control FP speed by switching between full current to the FP or reduced current through the FP resistor. When you crank the engine the PCM grounds FC which operates the C/O relay and B+ is sent…

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Doug Owner/Technician
California
Doug
   

Thanks Tony I found that the resistor is okay, switched it out with another. I'm finding that the reason why it starts and dies is because while the ignition switch is turned off the fuel pump is being temporarily activated through the c/o relay causing the fuel pump to activate momentarily. And then while cranking it has some pressure and then dies. I did find that it has a P0230 fuel pump…

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Tony Owner/Technician
Missouri
Tony
 

From what you wrote I still say the resistor CIRCUIT is at fault, but maybe I'm not understanding what you tested. Switching a good resistor for another still doesn't prove the circuit. I would load test from the FP relay's B+ output terminal (terminal 5, blue/black wire) to terminal 5 of harness connector IA4 (blue/orange wire, test the half with the female terminals). IA4 is the big white 26…

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Doug Owner/Technician
California
Doug
 

Thanks Tony, yeah I noticed that about the wiring diagrams one had different wire colors and even a wrong ECU connector pinouts. And actually I accidentally fixed it! The C/O Relay pin 1 to the E3 10 FC computer connection was shorted battery power which somehow was causing my errant ignition switch problem! While grounding that PIN at the relay I heard a snap like a fuse blue but it wasn't the…

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Doug Owner/Technician
California
Doug Resolution
   

So somehow I accidentally fixed this thing! On Pin 1 of the C/Opn Relay, the yellow wire to the Fuel Control computer connection was somewhere shorted to battery power which was causing the errant ignition switch problem!! While somewhat haphazardly grounding that terminal 1 of the relay I heard a snap like a fuse blew, but it wasn't a fuse, at least from what I could tell. It was somewhere in…

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Glenn Owner/Technician
Texas
Glenn
 

Hi Doug, Not to jink you but keep these notes in a special “What the Heck File” that you can access later. Also make sure you check for an excess Amp draw that may indicate something is staying on.

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Doug Owner/Technician
California
Doug
 

Good point Glenn thanks! Definitely learned a lot from this one.

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Tony Owner/Technician
Missouri
Tony
 

Good find. I led you down the wrong path by being so sure of a resistor circuit fault. It seems a few one in a billion circumstances combined to simulate that failure mode by affecting the C/O relay dynamically - as you were changing ignition start/run states. The fuse/relay box is made up of hundreds of thin metal conductor strips such that a cutaway would look kind of like the road map of a…

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Doug Owner/Technician
California
Doug
 

Yeah thank you Tony that's what I'm going to do next if it happens again! Even though this area has been really dry in Northern california! Never know it had to be something under there. Hey as far as the transistor no problem there. I bypassed it and then check the ohms and it was okay. And yes it was really strange how the ignition on/off position change was activating and affecting the…

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