Questionhi Todd, the 4x4 switch on dash is acting funny when i press 4L the 4H flass and when i press auto 4x4 the 4L will flass and what ever is flassing thats what it will go into and sometimes i have to keep playing with all of them to get the 2wheel drive to flass so it will go back to 2wheel drive. now a service 4wheel drive light is on. so a buddy of mine has a code reader and we hooked it up and it says (B2725) what does this mean? and what parts do i need to replace? thank you very much,mar
AnswerHi Mar,
Who is Todd????? I am in the question pool of unanswered questions. I am scanning the many questions that don't get answered by others, to see if I can help people, and I am seeing "HI TODD" alot. I don't see him as an optional expert.
Access to DTCs can simplify any system diagnosis. But these codes are not always 100% accurate. B2725 = active transfer case mode switch malfunction (the switch on the dash). It's always nice to have such an easy diagnosis, but should we assume that all B2725 DTCs indicate the need for a switch replacement? After all, General Motors TSB No. 02-0421-004 indicates a known problem with this switch assembly. Since you have a scan tool, lets verify before we just buy the switch.
GM has used many different four-wheeldrive control systems in its vehicles over the years, ranging from pure mechanical to electronically controlled. Each has its own diagnostic procedures, and the best source for understanding how these systems work will always be your information system.
The basic 4x4 system consists of a transfer case motor and encoder, Front differential actuator, transfer case module, speed sensors, switches and park input and output to the PCM.
The transfer case module data can be accessed with a scan tool such as the Tech 2, which is GM's official scan tool. It's always a good idea to make checking DTCs one of the first steps in your diagnosis.
The dash-mounted transfer case mode control is a set of normally open switches that vary the voltage supplied by the transfer case module when closed. The transfer case mod- ule sends 8 volts to the switches, then monitors the return circuit to deter- mine whether any of the switches is depressed. It can determine this because each switch has a different resistor in series with the circuit.
Simply press the buttons while watching the scan data. As you press various buttons, the scan data should indicate the proper input. Pressing "4HI" or "4LO" should result in the data stream reflecting that condition. Also, the LEDs on the switch would randomly go on and off.
The easiest way to confirm your problem is to tap on the button and watch the scan data along with the switch LEDs. When you do this, it can cause all kinds of random lights and data readings. It may even turn on the 4WD warning indicator. If this happens, it is obvious the switch has a mind of its own and needed replacement.
Hope this helps.
C J S
