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Home >> GMC >> 1998 >> Yukon 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 70 (Automatic Transmission Diagnosis - 4L80-E (Gasoline)) >> Diagnostic Tests >> DTC P0742: Torque Converter Clutch (TCC) Circuit Inoperative (Stuck On) >> Diagnostic Procedures

Diagnostic Procedures

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  1. Connect scan tool to DLC. Turn ignition switch to ON position. DO NOT start engine. Using scan tool, record freeze frame and failure records for reference. Data will be lost when DTCs are cleared later in this test.
  2. Using scan tool, verify TP sensor operation. TP sensor voltage should be .6 volt at minimum throttle position and 5 volts at wide open throttle position. If voltage is as specified, go to next step. If voltage is not as specified, see DIAGNOSTIC AIDS.
  3. Drive vehicle in "D4" range in 4th gear under steady acceleration with TP sensor angle more than 15 percent. If scan tool displays a TCC slip speed of -15 to 20 RPM while TCC PWM solenoid state is off, go to next step. If scan tool does not display a TCC slip speed of -15 to 20 RPM while TCC PWM solenoid state is off, see DIAGNOSTIC AIDS.
  4. Check for torque converter clutch mechanical failure. TCC is mechanically stuck on. Inspect TCC for a damaged or clogged exhaust orifice, converter clutch apply valve stuck in apply position, misaligned or damaged valve body gasket, or a restricted apply or release passage. Repair component as necessary, then go to next step.
  5. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Drive vehicle in "D4" with TCC off and throttle angle more than 15 percent. VCM must detect a TCC slip speed of 225-2500 RPM for 5 seconds. Select "Specific DTC" and enter DTC "P0742". If DTC P0742 is not present, repair is complete. If DTC P0742 is still present, repeat test.
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