I changed the transmission in my 11' Impala (It would not go in any gear) fluid was brown and lots of metal, (4T65E) and now the car will not start after changing it. When I turn the key to start it, the dash lights disappear but nothing else happens. The horn does not work either, it did work before. Also the indicator light on the dash for what range I'm in does not work. I see PRNDL but there is no square indicated which one I'm in. When I pulled transmission out I tied the rack to the vehicle and the intermediate shaft slid out and so when I got in it I turned the steering wheel and it just kept turning. But I hooked all the shaft back up. I have a wiring diagram and I am getting a 5v reference from the BCM to the ignition switch but I'm not getting 12v (only 3-4v) in the start position so I changed the ignition switch and nothing changed. A mechanic told me that the vehicle does not need to be programmed. Please Help!!!

Where did the trans come from? Meaning, what make, model, year?

If your not seeing a selector on your shift display, your PCM isn't seeing the trans selector. Or its not adjusted correctly. What happens if you shift the gears with the power on? Does the selector turn on?

When I turn the key to start it, the dash lights disappear but nothing else happens.

It'* normal for the dash lights to go out in the crank position, but the vehicle should crank over....



The horn does not work either,,,,,,When I pulled transmission out I tied the rack to the vehicle and the intermediate shaft slid out and so when I got in it I turned the steering wheel and it just kept turning. But I hooked all the shaft back up.

OOpsie.....By turning the wheel with the int shaft disconnected, you could have broken The SRS coil....your horn circuit goes through the coil.....I think you will have set a few SRS/SIR codes because that coil may be broken....



I have a wiring diagram and I am getting a 5v reference from the BCM to the ignition switch but I'm not getting 12v (only 3-4v) in the start position so I changed the ignition switch and nothing changed. A mechanic told me that the vehicle does not need to be programmed. Please Help!!!

There is no 5 volt reference voltage to the ignition switch....the ignition switch is powered by 12 volts from the BCM fuse.....and should be sending that 12 volts out of it'* three legs.....If you are only getting 3-4 volts out of the ignition switch, that is a problem.......with the key in the "on" position, what is the voltage across the battery? changing a tranny should not involve any programming.....

As Mike has suggested, if the ECM is not receiving a P or N signal from the TCM, the car will not crank over.....are you sure the transmission harness is attached to the tranny, on top(driver'* side)?

Also, as Mike asked, sure you have the right year and transmission for your car?

It came from lkq I'm not sure what year make model, it doesn't change anything when I move the shifter. I pressed a info button on the dash and it says this feature only available in park.

Would a broken SRS coil cause the vehicle not to start? Could that result in a voltage drop from 12v to the 3v I'm seeing at the start wire? the other wires show 12v when the ignition is in their position..

The Battery is new 12.6v and is a 800cca rating, however I did load test it at 400 cranking amps for 15sec and it only dropped to 11.6v.

The harness is attached to the transmission I probed the orange/black wire that goes from the ECM to the Internal Mode Switch and it shows 12v but I'm not sure how to check the wires that go from the IMS to the TCM..

If the display doesn't change when you change the shifter, then the PCM isn't seeing you make the shifter move. This means, its not seeing Park or Neutral. If it doesn't see these two, it won't allow you to start.

Did you transfer the trans selector from the old one to the new one?

Mike, I think he needs access to something like a Tech II scanner, to see if he has SIR codes from a broken clock spring(this will not prevent the car from starting), communication codes, TCM/ECM codes, and also to see if he is reading data from the tranny, as he shifts from P-R-N-D.......


Also I made a mistake......I looked at the wiring diagram too quickly....you are correct....there is a 5 volt circuit from the BCM, which goes through a resistor, back to the BCM, thus the drop in voltage(only in the key crank position).....the other two legs out of the ignition switch should have 12 volts.....terminal 3, Brown wire, feeds 12v to BCM, TDM, ECM, and TCM......term 1, Pink wire, also feeds 12 volts to the BCM, and powers the Ignition Main PCB relay.....both of those leads enter one harness of the BCM, and exit out of the BCM from a different harness to their respective circuits.......so if you have 12 volts out of the two legs of the ignition switch, with key in the "on" position, but don't have power out of the BCM, could have a BCM problem......

You are going to need a good set of schematics to diagnose this....

Is it a normal condition to see about 3v when the key is in the crank position at the white wire at the ignition switch? Because if that'* normal maybe the issue is with a bad IMS? And is their a way I can test it maybe with a multimeter? I don't have a scan tool with the IMS A/B/C/P PID... Just the Torque Pro app with a ELM 327 Adapter which doesn't even connect to the vehicle... Which I'm not sure if it isn't cable of communicating with this specific vehicle or if it that would mean more evidence that I have a bad BCM?

Yes, because you have 5V feeding a 1.3K resistor, back to the BCM....what you are reading is the voltage drop after the resistor.....

Not sure what an IMS is.....

Like I said, you need something like a high end scanner, like a Tech II, to see what is going on with your vehicle.....only a high end scanner can tell you if you have communication codes, SIR codes, etc., and also if you can communicate with all the modules......for example, if a module loses, power, ground, or it'* data line, it can't communicate.....if the BCM is not sending power to the ECM or TCM, there will be no communication and no start.......and you need schematics, schematics, schematics, schematics....

Sorry, I've been having computer problems, I did not transfer the selector since it is inside the transmission... With that type of selector switch is there a way I can use a multimeter to see if I'm getting a signal from the selector switch to the TCM. I am getting 12v from the ECM to the transmission connector.. Thank you for all of your help Tech II, and Mike, I really appreciate it!!