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Derek Werner
Derek Werner, Chevy Technician
Category: Chevy
Satisfied Customers: 135
Experience:  ASE Master Technician, L1 Advanced level specialist
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I have a 2003 suburban transfer case is in neutral getting a

Customer Question

I have a 2003 suburban transfer case is in neutral getting a p0306 code it was jumping from 4lo to neutral now it stays in neutral the ground behind the fender ir good
Submitted: 5 months ago.
Category: Chevy
Expert:  Derek Werner replied 5 months ago.

Hello and thanks for using JustAnswer!

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

If you could kindly rate my service it would be very appreciated. I will continue to work with you even after rated, and get notifications about any other questions you may have. I only strive for 5 star excellent service, Thank you for being a great customer.

Derek W

Customer: replied 5 months ago.
sorry I typed it wrong Its c0306
Customer: replied 5 months ago.
Already replaced the ecoder motor
Expert:  Derek Werner replied 5 months ago.

And you have already cleaned the grounds on the left frame rail?

Expert:  Derek Werner replied 5 months ago.

Do you have the np8 or np4 transfer case?

Customer: replied 5 months ago.
I cleaned the grounds Np8
Expert:  Derek Werner replied 5 months ago.

ok great, It is somewhat common for transfercase module to fail.

Have you checked for power and ground at the module?

Expert:  Derek Werner replied 5 months ago.

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.

Expert:  Derek Werner replied 5 months ago.

Here is a TSB for this concern.

Does the problem occur intermittently?

Customer: replied 5 months ago.
No I havent. This truck was working fine. Then it was in an accident hit in the drivers side wheel. After the body shop fixed it they went to move it and it went from 4hi to 4lo on its own. Then it went in to neutral. They put an encoder motor on it but it stayed in neutral.I can get my scanner to communicate with the abs eitherIts not intermittent its stuck in neutral
Expert:  Derek Werner replied 5 months ago.

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.

Customer: replied 5 months ago.
there was no wiring damadged at all
Expert:  Derek Werner replied 5 months ago.

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?

Customer: replied 5 months ago.
I have power and ground at the module . Im not looking for a quick fix . I hooked up the old encoder motor it goes into 4lo but cant switch it to anything else
Customer: replied 5 months ago.
Used an aftermarket encoder
Expert:  Derek Werner replied 5 months ago.

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.

Customer: replied 5 months ago.
I put a different encoder motor on it it shows the position 2 hi but I still cant get itto switch
Expert:  Derek Werner replied 5 months ago.

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.

Expert:  Derek Werner replied 5 months ago.

red and black wires.

Customer: replied 5 months ago.
i have power to pin e at the encoder motor nothing at pin d
Expert:  Derek Werner replied 5 months ago.

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.

Customer: replied 5 months ago.
There is a plug by the fuse box that goes to the encoder motor an tcase module all wires have continuity from that plug to the encoder motor
Expert:  Derek Werner replied 5 months ago.

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

Expert:  Derek Werner replied 5 months ago.

If all checks out good you have a fault in the Transfercase control module and it should be replaced.

Expert:  Derek Werner replied 5 months ago.

Hi i am just checking back in. Did you have any luck getting your 4x4 to work?

Have i answered all of your questions?

Thanks

Derek

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