B0770 06 Chevrolet Tahoe III

The TCCM detects 1.6 V or less for 1.5 seconds on the AWD indicator control circuit when the AWD indicator is commanded OFF.

Action Taken When the DTC Sets

Normal operation, the SERVICE 4WD indicator is not commanded ON. Driver is informed of fault via bulb inspection.

Conditions for Clearing the DTC

1. The TCCM clears the DTC once the condition for setting the DTC is no longer present.
2. A history DTC clears after 40 consecutive warm up cycles without a fault present.
3. History DTCs can be cleared using a scan tool.

Diagnostic Aids

1. A TRUE B+ has enough current to light a test light.
2. A DIAGNOSTIC B+ is a low current circuit that DOES NOT have enough current to light a test light.
3. A short to ground on the AWD indicator control circuit will cause the AWD indicator to remain ON at all times.
4. An open or high resistance on the AWD indicator control circuit will cause the AWD indicator to be inoperative during the 2 second bulb inspection.
5. An open in the indicator dimming control circuit will cause the 2 High, AWD, 4 High and 4 Low mode indicators to be inoperative during the 2 second bulb inspection.
6. The EL-49741: harness is a good source for 9 V.
7. The EL-49742: harness is a good source for B+ and ground.
8. With key REMOVED - opening a door puts a true B+ on the indicator dimming control circuit, TCSCS X1 pin 4. Other possible voltages are listed below: Door open, key removed - indicator dimming control circuit voltage = true B+. Door open, key in, key OFF - indicator dimming control circuit voltage = true B+. Door open, key ON, engine OFF - indicator dimming control circuit voltage = diagnostic B+. All doors closed, key OFF - indicator dimming control circuit voltage = B+ (high current - enough to light a test light). All doors closed, key ON, engine OFF - indicator dimming control circuit voltage = diagnostic B+. Key ON, engine OFF. Place a shop light on the DRL sensor. When the DRL sensor commands the headlights OFF, the indicator dimming control circuit voltage, TCSCS X1 pin 4, will go from a diagnostic B+ to a true B+.

Reference Information

Schematic Reference

Transfer Case Control Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

1. «Circuit Testing»(ref-364488-S04114729552010063000000)
2. «Connector Repairs»(ref-364488-S23771656832010063000000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-364488-S16423338542010063000000)
4. «Wiring Repairs»(ref-364488-S17530456672010063000000)

Scan Tool Reference

Control Module References for scan tool information.

Special Tools

1. EL-49741: 9 V+ Power Source Harness
2. EL-49742: Battery Voltage B+ and Ground Source Harness
3. J 35616: GM-Approved Terminal Test Kit