Rick's Free Auto Repair Advice

Service 4WD lite on C0327 C0327 P0836 P0500

How to fix a Service 4WD lite on C0327 C0327 P0836 P0500

GM has issued a technical service bulletin (TSB) 3061F to address problem with Service 4WD lite on C0327 C0327 P0836 P0500 on the following vehilces

2004-2006 Buick Rainier
2003-2006 Chevrolet Avalanche, Silverado Classic
2003-2006 Chevrolet Suburban, Tahoe
2002-2008 Chevrolet Trailblazer
2002-2008 GMC Envoy
2003-2006 GMC Sierra Classic, Yukon, Yukon XL
2002-2004 Oldsmobile Bravada

The problem shows up in “K” style trucks equipped with 246 and 263 transfer cases and results in trouble codes C0327, C0327, P0836, P0500. In “T” style trucks with 126 and 226 transfer cases, you may find just trouble code C0327. GM recommends following these diagnostic procedures:

For “K” trucks with 246 and 263 transfer cases, Visually check the TCCM wiring harness for pinched/chaffed concerns. In particular check the TCCM harness chaffing at the brake cable release spring. And check the pin/terminal fit at the encoder motor, TCCM and under hood relay center. Pay particular attention to Connector C1, pin A7 at the TCCM. Also check the TCCM, body, chassis and engine ground. 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.

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. Check the C151 connector on the left fenderwell for possible poor connection.

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

For “T” trucks with 126 and 226:
Check the TCCM wiring harness for pinched/chaffed concerns. Check the pin/terminal fit at the encoder motor, connector C101/X101, TCCM and underhood relay center. Check the TCCM, body, chassis and engine ground. 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.

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.

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.

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

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat


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