Rick's Free Auto Repair Advice

What does a C0327 code mean on a GM vehicle

A C0327 code on a GM relates to a problem with the transfer case motor or wiring

A C0327 code relates to the transfer case shift motor and can caused by a wiring harness or connector issue or a bad transfer case motor.

There are three C0327 codes:

C0327 07 Encoder circuit voltage above threshold
C0327 06 Encoder circuit short to ground or open
C0327 06 Encoder circuit signal invalid

First, understand how a transfer case motor works and communicates with the TCCM module

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.

image of transfer case shift control module

Transfer case shift control module (TCCM)

Here’s how to test the 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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