Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
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P0306 is a engine misfire code for cylinder #6. The most common cause for a misfire is a failing spark plug or wires. I would recommend starting with a tune up, replace the spark plugs, wires, cap and rotor.
If you have already cleaned the transfer case module ground connections the next best step to take is replacing the Transfer case encoder motor assembly. A position sensor is internal in the encoder motor and this sensor will fail causing the description you are describing. Click here
A high end scan tool is required to pull fault codes from the 4x4 module. Normally a fault code will be set in the system. I have had very good success replacing the encoder motor and no other problems occur.
If you have any other questions please let me know
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And you have already cleaned the grounds on the left frame rail?
Do you have the np8 or np4 transfer case?
ok great, It is somewhat common for transfercase module to fail.
Have you checked for power and ground at the module?
C0306 is indicating a fault in the t-case motor circuit.
Check for power at the module. Pin B connector c3.
Ground is pin A black wire.
Here is a TSB for this concern.
Does the problem occur intermittently?
It sounds like there may be a open in the shift circuit possibly caused by the accident. The a and b shift circuit should be checked for continuity from the t case module to the encoder motor.
ok well i am sorry to say there is no quick fix for this problem. You will need to perform some electrical testing to properly fault trace the concern. Pin tension should be checked at the module and encoder motor. Also like i said power and ground at the module, and ensuring the shift motor circuit wiring is not open or shorted.
Did you use a factory gm replacement encoder motor?
It is possible the aftermarket encoder is no good.
Another option is to replace just the encoder motor sensor in the old encoder. This is the part that normally fails.
encoder motor sensor.
Then you are going to have a wiring fault or a problem with the module. Next check the shift motor wiring.
Motor control A and motor control B
put a load through this circuit to ensure it can supply proper voltage to the shift motor.
do you have a wiring diagram for this?
Pins c and d at the TCCM connector c3 and pins D and E at the encoder motor.
red and black wires.
Power and ground will switch on these circuits to move the motor forward and back. To test you are going to need to access the t case module and check continuity on the circuits. or you could backprobe the circuits with everything hooked up and try to shift the motor to test for power and ground.
Also at the encoder motor ensure you have voltage on pin F orange wire.
ok great, I found a ohm reading for the encoder motor. Check for resistance at the encoder motor pins D and E, spec is between .5 - 10 ohms
If all checks out good you have a fault in the Transfercase control module and it should be replaced.
Hi i am just checking back in. Did you have any luck getting your 4x4 to work?
Have i answered all of your questions?