Rick's Free Auto Repair Advice

C0327 4WD

Diagnose and fix a C0327 4WD trouble code on GM

A C0327 4WD trouble code relates to the transfer case shift motor and can caused by any of the following:

C0327 07 Encoder circuit voltage above threshold

C0327 06 Encoder circuit short to ground or open

C0327 06 Encoder circuit signal invalid

What is a transfer case motor?

A transfer case motor shifts the vehicle into and out of 2LO,

C0327, transfer case shift motor

Transfer case shift motor

4HI and 4LO. The motor is equipped with an analog sensor that signals back to the transfer case shift control module (TCCM) whether it has actually completed the commanded shift properly. The transfer case motor mounts to the transfer case and engages with the transfer case sector shaft.

The TCCM provides a 5-volt reference signal and a low reference circuit (like a ground but with a set voltage drop). It receives the motor position signal on the encoder signal circuit.

C0327 TCCM

Transfer case shift control module (TCCM)

Diagnose a transfer case motor encoder signal

The following circuit tests apply to these vehicles:

2004 – 07 Avalanche 5.3

2005 C5500 Kodiak 6.6

2005 Express 1500 5.3

2003 – 07 Silverado 1500

2003 – 07 Suburban 1500

2003 – 07 Tahoe

2003 – 07 Sierra 1500

2003 – 07 Yukon

Disconnect the electrical connector at the transfer case. Using a digital voltmeter set to the 12-volt scale, with the Key in the RUN position check for the 5-volt reference signal on the light green/black wire. Check the black/white wire for good ground. If both check out, reinstall the electrical connector to the transfer case motor.

Next, backprobe the brown/white signal feedback wire while you operate the 4WD switch. Look for these values:

When the switch is set to 2 Hi, you should see 2.7 volts

When the switch is set to AUTO, you should see 3.4 volts

When the switch is set to 4 Hi, you should see 3.9 volts

When the switch is set to 4 LO, you should see 0.72.7 volts

If you don’t see those values, check the entire wiring harness back to the TCCM located under the dash behind the steering column. If the harness checks out, then replace the transfer case motor.

©, 2017 Rick Muscoplat

Posted on by Rick Muscoplat

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