DTC C0327 with or without Additional DTC Setting - keywords 03-04-21-001C 126 226 246EAU 263EAU

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

In "K" trucks with 246 and 263 transfer cases:

DTC C0327 stored in the TCCM only or C0327 in TCCM along with P0836 in TCM and P0500 in PCM.

In "T" trucks with 126 and 226 transfer cases:

DTC C0327 with or without additional DTCs setting.

For "K" trucks with 246 and 263 transfer cases:

This information supplements TSB 03-04-21-001C to include additional diagnosis.

Refer to published service procedures for diagnosing DTC C0327 which includes basic diagnostics i.e.:

1. Visually check the TCCM wiring harness for pinched/chaffed concerns.

Additional Info: In particular, check the TCCM harness chaffing at the brake cable release spring.

2. Check the pin/terminal fit at the encoder motor, TCCM and underhood relay center. Pay particular attention to Connector C1, pin A7 at the TCCM.
3. Check the TCCM, body, chassis and engine ground credibility. Remove and clean any material that may cause high resistance in the circuit i.e. paint, undercoating, etc. Ensure these grounds are secure and perform a voltage drop test and record the readings for these grounds. If the engine, chassis and body grounds are poor the encoder motor or the TCCM can be used as an alternative ground path.
4. If DTC C0327 can be duplicated in any position, check the scan tool data for the Encoder Signal Voltage going high or low. If the Encoder Signal Voltage is going high, check the Encoder Low Reference circuit for an open or high resistance. If the encoder Signal Voltage is going low, check the 5 Volt Reference and Encoder Signal circuits for an open or high resistance.
5. If DTC C0327 sets when making a shift into 4 HIGH only or during a slip event in auto 4WD, inspect the Transfer Case fluid for contamination. If fluid is contaminated remove the Transfer Case and inspect for mechanical concerns.

Additional Information: Ground Locations

1. TCCM Ground: G110.
2. TCCM Ground for the Mode Switch: G203.

Note: If there are no other component issues that share the same ground (example: On-Star shares G203) then it may not be necessary to check G203.

3. If no concerns have been found with the above checks, replace the encoder sensor.

For "T" trucks with 126 and 226:

1. Refer to published service procedures for diagnosing DTC C0327 which includes basic diagnostics i.e.:

1.1.	Visually check the TCCM wiring harness for pinched/chaffed concerns.

1.2.	Check the pin/terminal fit at the encoder motor, connector C101, TCCM and underhood relay center.

1.3.

Check the TCCM, body, chassis and engine ground credibility (Refer to published service procedures for ground locations). Remove and clean any material that may cause high resistance in the circuit i.e. paint, undercoating, etc. Ensure these grounds are secure and perform a voltage drop test and record the readings for these grounds. If the engine, chassis and body grounds are poor the encoder motor or the TCCM can be used as an alternative ground path.

1.4.

If DTC C0327 can be duplicated in any position, check the scan tool data for the Encoder Signal Voltage going high or low. If the Encoder Signal Voltage is going high, check the Encoder Low Reference circuit for an open or high resistance. If the encoder Signal Voltage is going low, check the 5 Volt Reference and Encoder Signal circuits for an open or high resistance.

1.5.	If DTC C0327 sets when making a shift into 4 HIGH only (226 Transfer Case) or during a slip event (126 Transfer Case, 226 transfer case in auto 4WD); inspect the Transfer Case fluid for contamination. If fluid is contaminated remove the Transfer Case and inspect for mechanical concerns.

Additional Information: Ground Locations

1.5.1.

TCCM Ground: G201 (part of Splice Pack SP201)

1.5.2.

TCCM Ground for the Mode Switch: G102

2. If no concerns have been found with the above checks, replace the encoder sensor.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.