B2799 AND P2716 ECU swap

Greetings everyone. I have a 05 Tacoma which developed a P2716 issue even though my trans shifts smooth. Only have a strong reverse engagement sometimes. I have followed the recommendations which involved in:
1) chasing the electrical lines from the trans unit to the ECU.
2) checking the solenoid
3) replaced the solenoid
4) replaced the trans wiring harness

I still have that P2716 code, so I have swapped out my ECU, last step, but I still get the P2716 code??

This is my question, just turning on the key without starting, the P2716 code immediately activates. I thought it would need the transmission on to get measured first? If I decide to completely swap the ECU, how would I be able to get the transponder to match the ECU so my keys work. I'm afraid if I do the jumper for 30 minutes will program my immobilizer and if I decide to use my old ECU, it wont sync. and my keys wont work anymore.

Please help.
Adolfo

 

Have you checked the wire all the way to and from the ECM?

 

I have checked all wires to and from. I have attached the new ECM and when I turned the vehicle into the on position and cranked it, the P2716 code came on. Just today I figured I would clear all codes and turned the vehicle off and then into the 'On" position and both of those codes are right there. I don't understand why the code would come right on without the transmission starting to test the fluid pressure.

 

I bet you have a wiring problem, it would be very unusual to have 2 PCMs with the exact same issue.
Did you load test the wires?

 

I did check the wiring for resistance. Popped out the solenoid and checked it. Replaced the wiring for the heck of it. I did notice that when I removed the PCM and attached it after a while, it lost its current so all stored codes erased. I turned the truck on and the MIL turned off until I put it in a gear (reverse). The MIL came back on. I guessing its the transmission.

 

This would be the result of the ECU detecting a fault that it doesn’t need a signal from the corresponding sensor because it can’t communicate with the sensor/solenoid on that circuit. Even if the sensor/solenoid had data to report to the ECU, it can’t be received by the ECU because the connection between them is not available/complete.

Side note: in relation to the codes your ECU provided, any code preceded with BXXXX signifies a problem with a component of the body electrical system such as immobilizer, and codes with a PXXXX indicate a problem that is Performance/Power-train related.

There a write up somewhere I’ve read before on how to deal with this scenario, I’ll try and find it for you.

See my response above. The fact that through all your diagnosis and different avenues of troubleshooting the main constant here is that the code is present without the vehicle running. This was my issue after a while of intermittent 2716 codes I would get reported by my ECU and then one day, it wouldn’t go away.

I know you’ve said you have inspected the wires and connections but I’m 99.9 percent sure that that is where the problem lies here for you. There’s most likely a loose wire that has separated at the blade pin at either your ECU on the E5 plug or at the other end of the wiring where the truck side latching plug is it’s very possible there’s a wire with a broken or failed crimp on a blade pin also. Make sure you check not only the signal wire for the shift solenoid D circuit but also that the ground wire it coincides with is adequately connected. I’d inspect it visually and check it electronically using a multimeter. I had used my multimeter on several occasions with no sign of problems and it wasn’t until I visually inspected the plug that I then spotted the cause of the problem.

It’s very easy to inadvertently damage the wiring at the plug ends by forcefully pulling on the wires of that plug when removing from it ECU or the transmission. Or if the plug has any damage to the plastic housing the blade pins are inserted into that can cause a misalignment of pins that when inserted to the other end allow the male and female pins to veer off and not actually engage each other to complete the circuit. Use a mirror or snap a pic with your cellphone to check the plug that is on the transmission and that it is corrosion free and all pins are present and pointing in right direction. It’s possible you could have a pin that broke off or has been bent sideways on the transmission side and has become stuck in the plug on the wiring harness side of the truck and no longer makes a connection on that circuit.

I would be very surprised if your problem was something other than wiring just based alone on the fact that this code is consistent though your troubleshooting and that it immediately presents itself when the key is switched to the on position without the need to actually start the engine.


Also, I’ve attached an example of what to look for at the plugs in regards to poor or failed crimps at the blade pins that would cause your problem. This example is pretty obvious in its separation but it may not be that obvious in your situation. You may need to even take it as far as removing each blade pin individually and confirm that the crimp is or is not adequate. If you do decide to take it to that extreme I’d suggest removing 1 wire/pin at a time allowing you to be 100% certain that each wire is correctly located on the plug and not accidentally reconnected a hole off leading to much bigger problems. Also, a decent depinning tool to make the process easier and to not cause additional problems by using a paperclip or other pokey thing that may seem ok but is actually causing damage to the plug housing or the blade pin that is not visible, which seems to be what you are chasing ATM.

If you do find damage to either the plug housing or blade pins, you can order the plug housing itself and/or wires that come with the pins already crimped ready to be spliced into your existing harness. Hell, I have a plug or two somewhere I can even send you if you need it. Although it may be faster to just order it from your local dealership as I can’t immediately recall the exact whereabouts of the spares I have.

 

Oh and hopefully you are using the correct literature for the P2716 troubleshooting as I just noticed the attachment you have in the first post relates to the a340/341 and the 5VZ V6 series transmission combination, which is not the same as what you have, being the 1GRFE V6 and a750 transmission. If you need I can email you the correct guide.

 

Bob!!! Maybe that's why I still have the issue. Can you send me the correct diagram, please. My truck looks nice parked on my driveway this whole time. I would like to register it and drive it!!! LOL
Adolfo

 

I posted the proper code chart for 05 in post #4, transmission wiring posted below.

 

Thank you. I will look at the diagram and work on it in a couple of weeks. I would rather just send it to your shop and pay you to fix it.
Adolfo