ECU swap question

Hello all!

I've recently been inundated in maintenance for my truck. Long story short I trouble shot down to a bad ECU. I've been trying to swap mine using flagship one. The stock part number that was on my truck was 89661-OCM72. Flagship one has sent me 89661-OCM71. Are there's interchangeable? Has anyone else used this company? The first ECU they sent me with this part number didn't work.

Back story:
Truck was power lagging up hills. I checked my injectors, replaced spark plugs, ohm'd coils, cleaned throttle body, installed catch can, fixed a major vacuum leak, and ohm'd the fuel pump & sending unit and wiring. I've also ran ats chemicals cro/crf 505 for cleaning. I also verified fuel pressures. The give away to me it was the ECU was the fuel pump was not turning off when key was switched to "on" and my long term fuel trims after fixing the vacuum leak went from -20 to positive 20.

 

Could it be the dreaded secondary air injection pump which dropped you into limp mode?
ECUs can be interchanged as long as they're for the correct engine. For ECUs I'd bite the bullet and acquire one from Toyota, or Toyota Parts Deal where you can get the correct ECU with a year's long warranty with it. Looking up both numbers they both appear to be correct, the 71 is just a year, and the 72 appears to cover 4 years. Additionally, could your vin number fall under a TSB to correct fuel issues and fuel pump? I would look into those issues first, reinstall the original ECU if you fall under the TSB and have Toyota correct your issues for free99.

 

I never had any codes for a secondary air injection pump. I'll look into the tab! Thanks for looking up that ECU information for me. I appreciate it!
So it's running fine until I get on a hill. Then it'll throttle back and pick back up, no lights on dash.

I also noticed the fuel pump turn off after 30 seconds on new ECU (that was programmed bad) whereas the original the fuel pump stays on. That's why I'm leaning towards ECU. It's pushed out a few miscommunication fault codes that I cleared and haven't come back and it's also commanding alot of fuel hence why I'm running rich.

 

I also cleaned my EGR valves. My entire truck had a ton of carbon in it. Even looking into the intake valves with the manifold off there was a ton of carbon which is why I installed an oil catch can.

 

For the Flex Fuels Toyota had issues with a lot of those and has replaced those pumps, that may or may not be your issue, you will probably require a reflash on your ECU which comes with the TSB.

 

You do know this is an ECU that controls just the fuel pump only right? They fail pretty often it seems. The Engine ECU I have never seen a single occurrence of it failing

 

I pulled the connectors off and checked wiring with a multimeter. It was good. Do you know any good tricks to testing the sending unit itself? I saw a post on here where someone bypassed their unit to keep the fuel pump on but other than that I have no idea how else. I've also hooked up a gauge to the fuel lines and the pressure was fine.

 

Update: ECU fixed it! The second ECU flagship one sent worked perfect. The ATS cleaner for fuel and oil lowered the idle and improved performance too. Anyone who sees this is say look at the myriad of symptoms your having if you're stuck between fuel pump control module and ECU. My truck wasn't stalling except in winter and I kept having codes pop for transmission PCM miscommunication and a bunch of others. I also had a misfire that woukdnt go away swapping coil packs/plugs/and wires were good.

 

I am having very similar issues with my 2012 5.7l 4x4 limited non flex. I bought a used ecu 89661-OCM32 but my original is 89661-OCM30. These codes were on the new ecu and then I put my old one back in and they transferred and now my truck will not start.

 

Your key isn't linked to your security system. You'll have to remap it to the old ECU IF the chip hasn't locked. See the picture. You can use a paper clip for this btw

 

Also ECU's have to be tuned to your vehicle and that needs to be done a by a pro. The only company I'm aware of that does "plug and play" is flagship one. The first one they send might not work but it'll log all the codes and they'll tune it so it matches and the second should be Gucci.

 

Very valid responses however, if you notice I have V18 techstream. I can remap my security, immobilizer, ect .. from TIS in a matter of minutes compared to the 30 minutes with a paper clip. But, just in case something didn't jive, I did that too! I also reinstall the original ecu and mapped everything back but the codes from the replacement ecu now are stuck on my original ecu because TIS cant clear the DTC's unless the truck starts and verifies the repairs have been made. Flagship 1 is not turning the ecu's. They are simply sending remanufactured ecu's that correlate to your specific vin and then they are deleting the original vin from the ecu and rewriting it to your specific vin before they send it out. As well as. Updating the ecu calibration (if needed) through TIS. It is a simple plug n play at that point. Different trim levels, years, and motors can use different wiring harnesses or tunes as you stated for flex or non, 4L, 5.7L ect...

 

Are you sure the codes transferred? They should be stored in the ecu it’s self. For it to trigger than many it’s almost like some part of the wiring harness isn’t fully plugged in

 

It's fully plugged in, I have run the ecu marrying process multiple times. I've read that the codes can also be stored in the throttle control module. So they appeared to transfer from the new ecu back over to the original ecu. Either that or by me putting in the new wrong calibration ecu it has in some way forced the original ecu to finally show that it was bad. I should back up some, I purchased the new ecu because I was having some fuel delivery issues with extended crank times. I bypassed the FCM and the truck was running better. I ordered the ecu before the fcm. I installed the new ecu with the fcm bypassed and it ran like shit. I reinstalled the original ecu with fcm bypassed and it ran great. I received the new fcm and thought maybe if I installed it and the new ecu and remarried everything that maybe it would clear up the poor running conditions and it didn't. I reinstalled the old ecu with the new fcm and remarried and now the truck will not start and all those codes are stuck there. It's almost like the ecu is locking out fuel injection completely. I have 30 something psi in the fuel rail. Truck will fire with starting fluid through the intake but will only turn over until that is burned up, nothing being injected. I'm at a loss, brand new plugs, coils, fpr, f.pump, maf, fcm. Everything has been multimeter checked. Only thing I can come up with is bad ecu and new ecu has the wrong calibration file for my model. And I have triple checked all fuses and relays. As well all of this is being done while on a good battery maintainer.

Like old vehicles, do I have to pull all these sensors and clean them or reset them??? Check and clean plugs, o2 sensors, I already did the camshaft sensors. My oil reeks of fuel now, do I have to do a full oil and filter change? One would think that the truck would still hold an idle and clean some of that up if it would just inject fuel into the cylinders.

I am going to login to tis through techstream and recalibrate the new ecu with my Vins most recent calibration and see what happens otherwise I do have an exact number for number ecu coming in a few days too so we'll see

 

The fact you mention the truck will run for 30 seconds on starting fluid would make me look at the fuel pump control module. Did you try removing the new one and going back to it jumped with the old ecu? Will the truck start and you be able to clear the codes.

If somthing is backwards in the new fcm I could see it throwing the engine ecu into all kinds of craziness.

 

UPDATE:
I am partial stupid and confused but, I do have the truck running! I was swapping ecu's around and noticed that you were correct, the ecu's were not seating properly. I corrected that issue.

The fcm's are still not communicating but if I eliminate them the truck runs really well with the jumpers. But only after I noticed a strange sound coming from the fuel tank. I could hear fuel pumping hard all over the inside of the tank. I pulled the fuel pump to find the hose was torn at both connecting points of the fuel pump housing. So it was a fuel delivery issues but that still leaves me stumped as to why the fcm's don't work. The way I have it bypassed is with pin 1 to pin 6 for 12v positive and pin 2 to pin 3 for negative. That is controlled by the key on position relay. I think I'm going to install a relay to a switch and just control the fpump that way moving forward and eliminate the fcm altogether. The truck is running much better this way.

 

What a s*** show haha do you have obd screen shots of before and after? My new ECU didn't fix my power lag problem after all. I got the launch cr919e to relearn the alcohol density and already the truck started up beautifully. I'll be able to test it on an upcoming road trip. I'm curious as to the similarities in problems we've had. It seems to me the fcm doesn't have any fault codes it throws and it would make someone's life alot easier if we had obd data to prove when it goes bad and how to prove it isn't.
I saw another post where a fellas throttle body wiring harness had a wire break internally at the bend at the back left of the engine block and that was causing his problems.

 

I will upload some data shots as soon as I can, I also found the bank 2 sensor 1 wires had coating breaks on all of them. I cut the wiring harness and put heatshrink over every wire and then re soldered them back together. As far as my fcm, I eliminated it completely. All it is, is a voltage reducer.it can reduce 12v to whatever volts for different fuel pump duty cycles. I can say this, I have 35" tires and ever since I bought the truck, the best fuel mileage I have had is 9mpg but mostly on average 7.1mpg, now after eliminating the fcm. I am averaging 15-20mpg. So screw that thing. I installed a quick connector to jump wire 1 and 6 and 2 and 3 together. Then put the ecu signal wire and the diode wire into a dead end connector. See you buy! I will post the data at some point over the next few days. Power lag could be maf, exhaust manifold leak at the secondary air injection pipe connection, O2 sensors, or the throttle body sensor which means replacing the entire throttle body. I did that 2 years ago. Those are the fixes I have needed every time I had poor performance but most of the time it has usually been my maf sensor. I have needed to replace my 3 times since 2019. You have to install a hitachi or a direct oem toyota hitachi maf or the ecu will reject it within a few months or weeks or days lol.

 

Also can't remember if I mentioned this or not, flagship ecu's are not necessary as well as, part number for number for ecu's what is required; a obd 2 tool capable of vin read and rewrite or a j2534 vci cable and v18 techstream setup for patch use (which I can assist with setting up correctly for use with 64bit OS. A jumper pin for ecu marrying process through obd connector, and a battery maintainer. The scrap yard ecu's vin needs to be searched to verify that the previous trucks motor and trim features match i.e. 4x4, tow package, 5.7l or 4.6l, flex fuel or Gas ect.... Now that I know my wiring harness wasn't fully seating, I have successfully programmed two variants of ecu's to my truck for $100 to $125 a piece.

 

Would you happen to have any advice on the ECU swap from the secondary air injection pump? I entered the limp mode and realized the ECU as no voltage from the fuses / wires on the right side starting where the CIG fuse below. However, only one (1) of the CIG outlets has not voltage and the other do. I am open to hear your input, if possible. I am leaning towards replacing the ECU right now.

 

Replacing the ECU may not solve the issue, I would check fuses and relays first. If you have power to 1 side of the engine, but not the other, look gor those relays and swap them. If you still have an issue trace out the wired and look for damage or rodent presence who dined on your electrical wires. if all these have checked out, maybe look into a by pass for the SAIP. If you're in a state that requires inspection you may need to look at the parts from O'reillys, clean and rebuild them.

 

Perfect! In fact, I’ve began looking into testing those relays. The only concern is the previous owner replaced these fuses with ones of a larger size at least 5amps. Would you happen to know if any other visual differences if the ECU was blown or. Would the only way to see that is opening it up?

Thanks for the response, it’s reassuring to have your input on this. I appreciate it.

 

A good place to start would be looking up tje Electrical wire diagrams here:
https://www.tundras.com/threads/ultimate-tundra-wiring-diagrams-collection.81448/

Figure out why power is not getting to the ECU. It may not be the ECU as it is properly grounded, a surge in electrical power would fry the fuse or relay. More than likely a wire or ground may be damaged. Have you been able to pull codes?

 

That’s the difficult part, the same code pops up after replacement of the Secondary Air Injection Pump bank 1 (P2445). The code comes on and goes off, but the truck enters limp mode. The pump is silent but runs briefly, intermittently, on cold starts. Here is what I performed that led me to the lack of voltage to the ECU.

- Performed resistance testing on SAIS. Seems to run per manual.
-Inspected the hoses on the SAIS, all good.
-Wire harnesses don’t looks bad, and continuity and voltage are present. They are aged, but functional.
-performed voltage test with batteries and fuses, found that I have a short but not inside the engine bay per test.
-Ran voltage on the notorious cigarette outlets, to find one without voltage. Followed the wire diagram to notice the incorrect fuse and not voltage.
-Currently disassembled the ECU and wires (female/male) look intact and good.

My next step is to remove the dash and follow the CIG wires and/or find the ACC relay to test, wherever that is. (Or perform resistance on the connectors for that)

if you have any other lead, that would be helpful. Also, is the short pin suppose to be loosely inside the fuse box? When it’s fixed my truck doesn’t start. Keeping it loose allows my truck to remain somewhat functional.

 

Sounds like you have an electrical issue. You may need to inspect the fuse box wiring. The SAIS will dump you into limp mode, even if you replace the ECU. If there's a short attached to that circuit then your issue should be there, loose bolts in the fuse box is probably a red flag since you're grounding out a circuit if you bolt it all the way in?? You may need to look at where it's making contact and grounding itself out. Intermitent light coming on ... I had an electrical issue when my Tundra was new, it was due to an undisclosed accident, after 2 years of killing batteries stealership resolved the issue, just took 12 batteries on their dime.

 

There's a rebuild method someone posted on the SAIP thread... On the filter portion in the pumps.. I don't rememver the member's username but it was about June, 2021 or before... I remember because I had bookmarked his some before I transferred to SoCal. It was an O'reilly part number.

 

Thank you! I’m currently disassembling my dash to and checking wires today - checking the ground points too.

I will add the search for that post and checking the harnesses from the fuse box. I’m hoping to figure this out today. So, I truly appreciate your help, as I’m trying to save some money. I’ll keep you posted if I find the culprit.

 

I had no luck with Flagship one. The Truck started and ran OK but I kept getting a code for O2 sensors after some POS stole the Catalytic converters the dealership said they burned out the circuit on the pcm where the O2 reports. I tried Flagship one and followed their instructions to sync the new pcm but after 4 times sending it back and getting another it still won't start. Before it would start and drive but just had a code. Now it's AFU. It's just yard art.

 

You may need to trace the wire into the cab and check for a damaged section. Maybe a damaged ground which will still trigget the code.

 

It's too late now. Flagship one's junk messed up my Truck now it won't start it turns the engine but it won't fire