Lexus C/OPN Relay issue.

Lexus4321 · 10-03-2020, 02:11 PM

2006 Lexus GX470.
Looking for advice here. I had to remove my intake to do work under the intake, also installed new injectors and plugs. Had the batt disco'd for days. Put everything back and the ECU will not ground the C/OPN relay coil so the C/OPN relay can supply +V to fuel pump relay. Everything else seems ok (voltage is there at C/OPN relay, pump works, no DTC's, all fuses are good, etc etc). The ECU pin that controls the C/OPN relay coil is the "FC" pin on ECU (common collector transistor most likely). From the wiring diagrams the "FC" wire between ECU and C/OPN relay appears to be a homerun wire, which makes sense from a safety perspective.

I found this post in this forum. Dealer told him "some connectors". What connectors could it be? Could it also be the immobilizer? Not much info about what the immobilizer does. Does it serve as a security feature and safety feature if say an airbag is deployed, cutting off the C/OPN relay?

Mechanics, need help understanding Toyota fuel pump problem

Lexus4321 · 10:27 AM

Well, after a bunch of testing it seems my fuel pump went south. The ECM, relays, fuses, sensors, all seem to be ok.

I suspect, when the fuel rails and lines there went empty and was just air after install, when the pump cam on it has no liquid resistance and probably took a dump. I can run the pump manually and some fuel come out of the fuel line, but it's not 50psi. It also sound funny when the pump is running. I am now in a project to replace the pump. But get this, there's a access panel under rear carpet BUT NOT BIG ENOUGH TO REMOVE PUMP THROUGH! Yeah, I am not dropping the tank, just gonna cut open what's needed and TIG it back into place.

With Toyota, the ECM code will not engage C/OPN relay until the ECM gets the START (starting) signal AND signal from crank sensor. Once the engine is running (I assume a rpm threshold) the ECM will keep C/OPN relay energized, which feeds the pump selector relay, etc.

And just to note, I am not mechanic by trade, I just a DIY'er with a lot of tools

GH85Carrera · GH85Carrera's Garage

So you are going to TIG weld right above the gas tank and the fuel pump. I would suggest you do that outside and have a fire extinguisher close by and an assistant to put you and the car out if it catches on fire.

fastfredracing · 10-06-2020, 01:25 PM

Quote:

Originally Posted by Lexus4321

Well, after a bunch of testing it seems my fuel pump went south. The ECM, relays, fuses, sensors, all seem to be ok.

I suspect, when the fuel rails and lines there went empty and was just air after install, when the pump cam on it has no liquid resistance and probably took a dump. I can run the pump manually and some fuel come out of the fuel line, but it's not 50psi. It also sound funny when the pump is running. I am now in a project to replace the pump. But get this, there's a access panel under rear carpet BUT NOT BIG ENOUGH TO REMOVE PUMP THROUGH! Yeah, I am not dropping the tank, just gonna cut open what's needed and TIG it back into place.

With Toyota, the ECM code will not engage C/OPN relay until the ECM gets the START (starting) signal AND signal from crank sensor. Once the engine is running (I assume a rpm threshold) the ECM will keep C/OPN relay energized, which feeds the pump selector relay, etc.

And just to note, I am not mechanic by trade, I just a DIY'er with a lot of tools

Ill second the bad idea. You will have residual fuel everywhere, and fumes . Can you loosen, and lower the tank just far enough to wiggle the pump out ?
I have a few buddies who have caught cars on fire. You will have saved no time if you burn your garage down. In this situation, you will be in the car, right smack on top of the fuel tank , with no way to escape when the fireball comes at you . Don't be a crispy critter

Lexus4321 · 05:50 PM

I understand your concerns. There will not be fuel and fumes. Once the pump is replaced it's basically sealed up. I can then do a mild wash down of the area. The top of the tank in that area will get covered with welding blanket. I will probably just opt to do some TIG spots as needed (1 per inch, etc) and then seal up the rest. Or I might flange the cutout piece, butyl rubber under the flange, stick it, then just tack flange to body in a few places to hold it (making it ez for another entrance in the future). The original access panel will remain, etc.

I am a pro TIG'er

No, there is no way to drop the tank just a bit. There a bunch of hoses and connectors that need to be undone, then the tank has to be taken out completely.

Took just 40min to get to the access panel under the carpet (me going slow and took both seats out, etc). Why Toyota did not make a real FP Replacement access panel is beyond words.

Yes, I have fire extinguisher, but I don't think it will be used

Lexus4321 · 03:31 PM

Here's the prep & cut. Used a fine tooth blade, and had to drill out 3 spot welds. I did manage to break a clip that cannot be replaced on it's own, but I will deal with that. Notice how the cut on right is far enough back that it's in the hat channel so I did not need to cut the edge of the hat channel off. This looks like enough room, but if needed I can trim the edge of the hat channel.

I am waiting on some parts and ring tool to finish the pump swap, but going back to TIG'ing it, I think for safety reasons I will TIG the seams 100% and then TIG tack back where the spot welds were. Then will clean/prime the area (underneath I can reach with my hand, so maybe a wipe of some sort to protect the metal) and then just a quick shot of white spray. Like it never happened

1990C4S · 10-07-2020, 01:58 PM

It would not worry me to tig weld that.

Does it even need need to go back in?

Lexus4321 · 10-07-2020, 03:30 PM

Quote:

Originally Posted by 1990C4S

It would not worry me to tig weld that.

Does it even need need to go back in?

I do hwy driving. A at-speed crash or rollover could cause the plastic tank to rupture or lines to rip off, don't want fuel easily spilling inside the vehicle.

So for shear safety reasons I will completely TIG it back like it never happened, etc.

I just did not want to muck around with hoses/clips/connectors of dropping the tank. This is a 14.5yr old vehicle and it's showing signs of dry-rot on plastics and stuff, more so outside than inside. So to avoid that headache I went this route, etc.

And while I have the carpet up, will add some 50mil sound deadening mat to make this boat a tad more quieter inside.

908/930 · 908/930's Garage

You could just weld tabs on the part you cut out and fasten it back with short screws, that way you can remove it easily next time.

Lexus4321 · 10-08-2020, 07:37 AM

Quote:

Originally Posted by 908/930

You could just weld tabs on the part you cut out and fasten it back with short screws, that way you can remove it easily next time.

Well, I thought about it, but then reality sinks in.

The OEM pump/filter went 14.5yrs and 225kmi. The new parts should last as long or longer. I am not likely to have this vehicle another 14yrs and the engine most likely won't make another 225kmi w/o needing major rebuild.

So, I believe this is a 1-time thing, thus I will just close it back up like it never happened, etc.

GH85Carrera · GH85Carrera's Garage

Just be sure to get a OEM pump from Lexus and not some garbage cheap pump made in China.

Lexus4321 · 10-08-2020, 09:28 AM

Quote:

Originally Posted by GH85Carrera

Just be sure to get a OEM pump from Lexus and not some garbage cheap pump made in China.

A lot of the Denso stuff is MIC.
I am installing a URD pump kit (USA Walbro pump with an additional external filter).

Today I prepped the metal edges for TIG work to be done. Just waiting on pump kit and ring tool to arrive.

fastfredracing · 10-08-2020, 01:22 PM

I hate that when they give you an access panel, and the thing does not fit through the hole anyway. What is the point even?
I have run into this with SAAB, Audi, and I think I remember a Toyota getting me before .
Its kind of like :

Be careful either way, you will spill some fuel

john70t · 10-08-2020, 01:30 PM

PDF of the Lexus C/OPN
https://www.clublexus.com/forums/gx-1st-gen-2004-2009/954167-that-tricky-c-opn-relay.html

Prius info on the relay. Not the same thing but a good discussion.
https://priuschat.com/threads/need-to-know-where-the-c-opn-relay-is-with-image-if-possible.153355/#:~:text=C%2FOPN%20relay%20is%20part%20of%20the%20 integrated%20relay,but%20not%20start%20%28Prius%20 cranking%20sound%20like%20running%29.

Lexus4321 · 10-09-2020, 11:04 AM

posts #13 & #14.

TY for that.

Yeah, I read all about the C/OPN relay (that's my thread on Clublexus, etc), I studied vehicle wiring diagrams. What's hard to find is how the ECU uses input data to know how outputs will work. I have it all down now, and all seems ok there.

Yeah, a little fuel might spill, but the interior floor will have plastic over it, and any that gets on the tank will be washed out later. I am not really concerned here.

Lexus4321 · 08:20 PM

Update:
Good news, pump canister made it out w/o additional cutting. My initial guesstimate at the opening size was just enough.

The float sending module looks like toast, so a new one will go in.

The new pump is a Deatschwerks 255 lph unit.

And for those needing to splice wires in the tank, I offset the cuts (so the two wires can't touch each other), do a linear twist if the wires can be soldered (see note below), solder it, and then use Kynar (or the like) PVDF or FEP heat shrink tubing over each joint (slip tubing on 1st, etc, McMaster, I chose PVDF )

Note: some OEM's use wire that have coated strands of copper which cannot be soldered, or just not copper wire at all. In these cases crimp the wire ends into a barrel connection, then fill heat side with solder iron, put some solder into barrel, etc. If you scrape the wire strands carefully with a razor and see copper underneath, then try and scrape some to expose some copper, crimp then solder, etc.

Lexus4321 · 10-16-2020, 08:45 AM

Sadly, new pump did not resolve the issue.
I will run some TechStream diag to see where that takes me.
I am still leaning on fuel delivery issue.

asphaltgambler · 10-16-2020, 11:30 AM

^Whaaaaaa?^^^^^ all that and same problem? Man...…..

Lexus4321 · 03:50 PM

Quote:

Originally Posted by asphaltgambler

^Whaaaaaa?^^^^^ all that and same problem? Man...…..

Yep.

At least it now has a better fuel pump and a new fuel level sending unit

My Techstream finds nothing wrong. I wonder if the 'new' fuel injectors are stuck closed (not very likely, they had just come from being serviced), or maybe a bad cam sensor? The no-start sounds like bad timing by ECU.

Fuel tank was filled up past 3/4. Maybe the return valve on the fuel rail is goofed not allowing pressure to build? Techstream does not seem to have a Fuel PSI monitor.

Frustrated at this point.

mattdavis11 · 04:47 PM

My bet is the immobilizer. You could have lost the program when the battery was out of the car. You will know if it has lost the program if the key illumination on the dash when the key is in the ignition II position is not lit up. Try placing the fob right next to the push button start then press and see if she fires up. The battery in the fob might be dead, and that procedure is a fail safe way of starting the vehicle when that small little battery dies.

You can try this too.

https://forum.ih8mud.com/threads/efi-relay-bypass-kit-immobilizer-fix-for-uzj100-lx470.952811/