I have a 2003 Dakota STX and the 4 wheel drive switch has gone crazy. When you first turn the truck on all of the 4 wheel drive lights will come on but then they all go out they burn very dim. Also the service 4 wheel drive light comes on. I can not get the 4 wheel drive to work. I have replaced the TCCM and that did not fix the problem. I also checked the TCCM to make sure that it was reading the right voltage and it check out all right. Do I need to disconnect the battery and reset the computer or do I have another problem. Thanks.

 

Welcome to the forum.

What do you mean "reading the right voltage" - where exactly?

Double check the grounds for the TCCM.

You can try disconnecting the battery.

 

I have 12 volts coming in to the TCCM, I have floating voltage 16pin black plug, and I have 5 volts on the 16pin Gray plug. Which every thing that I saw tells me that the TCCM is working right.

 

Each of the indicator lights is "hot" all the time. The grounds are switched to enable them. The selector switch is multiplexed so the resistance will vary depending upon what position it is in. The mode sensor is basically just a switch.

The service 4wd light indicates a code is stored.

Can you post the voltages from each pin?

C1 BLACK
A1 PCI bus
A4 4wd low indicator
A5 4wd high indicator
A6 mode select
A7 mode sensor ground
A8 5v supply
B4 neutral indicator
B5 default indicator
B6 mode sensor D
B8 ground

C2 GRAY
A1 Mode Sensor B
A2 Mode Sensor A
A6 Park/Neutral
A8 5v supply
B2 Mode Sensor C
B8 5v selector switch feed

C3 - to shift motor
A ground
B battery
C shift motor A
D shift motor B

 

These are the voltages I have got.
C1 Black
A1- Jumping
A4- 10.13
A5- 10.14
A6-.79
A8- None
B4- 10.29
B5- 10.09
B6- 4.95
B8- None

C2 Gray
A1- 4.96
A2- 4.96
A6- .08
B2- 4.96
B8- 5.05

C3 Black
A- 0
B- 11.79
C- 11.78
D- 11.78

 

C1 pin A7 is? Should be ground.
C2 pin A8 is? Should be 5v.

From what I'm looking at, your transfer case mode sensor isn't working correctly or has a bad ground - C1 pin A7.

Mode Sensors A, B, C, and D are all showing 5v. One of them should be showing ground.

 

I have gone back and rechecked the voltage on C1 pin A7 and I have no voltage on it. I have also rechecked C2 pin A8 and it has 5v. Mode sensors A,B,C, and D all of them are still showing 5v. Would you replace the transfer case mode sensor and see if that is the problem. And where could I find one without having to go to the dodge dealership? Also can I just replace the mode sensor or do I have to replace the whole thing including the shift motor.

 

When you made these measurements were you disconnecting the connector(s)? They should be connected.

I haven't been able to find just the mode sensor.

I've attached a page from the FSM with the mode sensor outputs for each transfer case position. In no case should all 4 channels be "high." That's why I suspect it has failed - it's an electronic switch/hall effect assembly.