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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 P0712: Trans. Fluid Temperature (TFT) Sensor Circuit Low Input >> Diagnostic Procedure

Diagnostic Procedure

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  1. Ensure transmission fluid level is correct. 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. Read TFT sensor signal voltage on scan tool. If TFT sensor signal voltage is less than .2 volt, go to next step. If TFT sensor signal voltage is more than .2 volt, see DIAGNOSTIC AIDS.
  3. Turn ignition off. Disconnect transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine. If TFT sensor signal voltage is 4.92 volts, go to next step. If TFT sensor signal voltage is not 4.92 volts, check for short to ground in TFT sensor signal circuit. Repair circuit as necessary, then go to step 8). If circuit is okay, go to step 7).
  4. Turn ignition off. Install Jumper Harness (J-39775) on transmission side of 20-pin connector. Using a DVOM, measure resistance between terminals "L" and "M" of transmission 20-pin connector. See Figure. If resistance is 3333-3689 ohms at 68°F (20°C), go to next step. If resistance is not 3333-3689 ohms at 68°F (20°C), go to step 6).
  5. Measure resistance between ground and terminal "L" of transmission 20-pin connector. If resistance is less than 50 k/ohms, replace wiring harness. If resistance is more than 50 k/ohms, see DIAGNOSTIC AIDS.
  6. Disconnect TFT sensor connector. Measure resistance between TFT sensor terminals. If resistance is 3333-3689 ohms at 68°F (20°C), see DIAGNOSTIC AIDS. If resistance is not 3333-3689 ohms at 68°F (20°C), replace TFT sensor, then go to step 8).
  7. Check VCM and connector for damaged or backed out terminals, weak terminal tension and poor connections. Repair as necessary, then go to next step. If terminals and connections are okay, replace VCM, then go to next step.
  8. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P0712". Ensure TFT sensor indicates a voltage more than .2 volt for 10 seconds. If DTC P0712 is not present, repair is complete. If DTC P0712 is still present, repeat test.
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