O/D button on a 2005 Tundra

Hi All -

I recently had my center carrier bearing and U joints replaced on my Tundra (Auto, 4.7 LTD DblCab). While it fixed the vibration that was happening, now it seems at any speed once I get through even a couple of gears, when I hit the OD button there's no change in RPM and it feels like nothing is engaging.

Is this something as simple as maybe a cable or part of a wiring harness getting disconnected?
I honestly don't know and I'm not gonna just jump to conclusions, shade tree mechanic that I am.

Also, some thing that didn't exist before I had this work done is the check engine light is now on and it tells me the code thrown is for the knock sensor 2.
Are the two connected?

Looking for places to start.

Thanks and hope ya'll are having a great weekend!

 

In most vehicles I've owned, at highway speed, if you tap OD, there's typically a slight change in RPM. I totally forgot to try this in my truck on the interstate Friday after we chatted. And I didn't crack open the manual to read what it says about the OD button and its behavior.

As for the knock sensor - two things to share. One, rodents like to crawl up and nest in the human-inaccessible void under the intake manifold where both knock sensors and the starter live on the V8/4.7 2UZ. They'll chew the wiring. Two, I had the same code recently, but there were no symptoms, like I couldn't hear a knock at all. I'd just filled up at a Kroger grocery store gas station, and it turned out it was just bad gas. I cleared the code and moved on. I'll never buy gas at Kroger again.

Knock sensor is literally listening for knocks and pings, they're directly attached to the block. So anything that could cause a knock - like bad gas! - can cause a knock sensor to throw a code. Did you fill up with gas recently at a different station?

 

Unless it's burned out, does your O/D OFF light come on ?
That button has been known to have issues over time with the conductor leading to the button....grounding out or becoming open.

 

Was looking at a previous thread you started and while this may not have anything to do with your present O/D issue, do you mind posting the instructions if possible.

Also, when you say "specifically for my truck's VIN", do you know or recall, did it have the same part number as your initial ECU ?

That would be some useful info to add to your thread you started couple months back with no closure on your issue. It might help someone in the future that runs across that thread with same problem.

2005 Tundra Double Cab Driveshaft ...

 

Hey @BubbaW -
The OD light does come on when I press the button and then goes off when I press it again. But nothing seems to be happening as far as an RPM change. I'm gonna try to get it out on the highway tomorrow so I can get some speed on it and see if that makes an rpm change more noticeable when I hit the button.

Great point about the Driveshaft. I need to post an update and will (I got the vibration corrected and it was the first thing that had been mentioned with the carrier bearing and U joints).

You mentioned posting the instructions...is that in regards to the ECU? If so, I'm glad to do so. Should I start a new thread for that?
As far as the unit having the same part number, I found a company online and this is the only thing they do is computer modules for vehicles. They needed the VIN to my vehicle to provide the specific unit and updates necessary, which were installed by me via the computer code reading porch under the dash on the driver side.

 

@shifty` -

I did fill up the tank before I brought it to the shop for them to do to work on the driveshaft, and it was from a place I don't normally go to. The check engine light wasn't on to my recollection when I dropped it off.
If it's the fuel, should I top off with high test? Should I pour an additive into the tank? Do I let the tank get closer to empty and then fill it up with fuel from a station I normally go to?

 

More curious if the part# of the old ECU matched the part# of the replacement.

 

I put a full bottle of Seafoam in the tank and burned through it, then added another bottle of Seafoam on the next tank after filling up.

 

Will be curious of what you find as far as RPM change if any given you mentioned in your other thread you have few hills if any to test on.

If what they put on the flash drive is too large, perhaps I can get that some other way. I have not seen instructions posted in our forum concerning ECU programming and thought it would be nice to see. See no reason to start another thread IMHO.

As for the ECU they sold you, I was wanting to know if the part # they sold you matched the part # of your original ECU, irrespective of what they sold you via your VIN #

 

@Bubba -

I honestly don't know how to transfer the data off of this flash drive since I don't have a reader other than the port in my truck. I have attached the instructions that came with it, and that's the drive in the upper corner.

As for the ECU, it looked pretty much exactly like mine, but I honestly don't recall what the part number was. I know they needed my vin, because when I went online and ordered what I believe was the right part, customer service called me back to confirm my vin number and said it required a different unit than the one I ordered. They also said having the vin number allowed them to provide all the necessary updates which meant I would not have to go to the dealership and have them flash the updates. I did the install in front of my house and honestly it took me longer to take apart the glove box then to remove and install the new unit.

I just researched my email and found the following:
The part number as indicated by the company is 89661-0C642.

The Company I ordered from:
https://www.fs1inc.com/

 

Thanks and understand fully.

Not that this info will help but what caused you to change the ECU and did you also have to change the harness cable ?

As for the O/D OFF issue and you mentioning few hills if any in your area, hopefully you do not have to resort to troubleshooting if the signal is actually getting to your ECU.
However, at least you know where it is

Given you mentioned a knock sensor code has now surfaced, I'll throw out some comments that may or may not relate, only that it might be a connector not fully seated.

As the below drawings show, the knock sensors and the O/D Direct Clutch Speed Sensor(DCSS) are both part of connector E6 of ECU.

If it comes down to troubleshooting the O/D switch, O/D DCSS and/or knock sensors, those pages from 2005 FSM can be made available.

 

FS1 is a reputable company. But I would still look at the old unit (if you still have it) and confirm the part numbers match OR post both part numbers here if different and I can do a quick dive on the part#s to confirm one is a supersession of the other. But that's lower priority than what Bubba is talking about.

 

Hey there, @BubbaW , I appreciate the images even if I don't know what the heck I'm looking at. I have a rough idea but my knowledge when it comes to electrical is highly limited compared to my Shadetree mechanic ability, which is in and of itself pretty limited.

If I can figure out any way whatsoever to copy this drive and get it to you or get it posted somewhere online, I will do so.

When they sent me the replacement ECU, I was thrilled to discover I did not have to change the harness or any of the plugs. Each of the connectors can only fit into its specific receiver port, as you likely are aware. They told me I wouldn't have to change anything and they were right.

I noticed my gas mileage started decreasing rapidly and dropped to about a third of its performance. When I hooked up my simple reader, the codes it gave me were for the ECU.
Doing more research I discovered a failing ECU could lead to a host of other challenges and I couldn't afford that. So further research provided me the company whose name and website I attached in a previous post.
Upon replacing the unit, my gas mileage returned to what it was previously.

I know that's not very scientific, but that and the fact I wasn't getting any codes told me I'd probably done the right thing.

 

@shifty`

I don't recall if I kept the old unit or not. I didn't have to do a core exchange, but I feel like I still have it in my garage. I just have to figure out where. If I find it, I will share the part number.
I appreciate you for offering!

 

@Brad Majors

I can understand/accept that some do not grasp electrical drawings but unfortunately, certain issues do crop up and one needs to know how the circuit is working or they can spend big bucks troubleshooting the responsible circuitry for them.

That said, all I was really trying to show is that those red rectangular boxes I added, show that the knock sensors and the O/D DCSS go to or from the ECU via E 6 connector of ECU. May not be related but it was just a thought of something might needing checked….connector not fully seated.

 

You are right and I was under selling myself. When I restored my 1972 mock one, the only change I made to it was to put in the racing cluster from an 85 Mercury Capri. I had to trace every wire and create my own diagram to make sure everyone of those wires were connected correctly. I wound up creating a very crude version of what you shared.

I will check the ECU connector because that's a great suggestion.

 

@Brad Majors I totally forgot, I went and did a button punch and just noticed while I was pulling pics of my new wheels off the phone.

But it looks like I deleted the damn video just now. Long story short, at 75mph, punching OD button dumps the gear and pushes me from ~2200 RPM to the upper 2000s.