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Home >> GMC >> 1998 >> Yukon RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 70 (Automatic Transmission Diagnosis - 4L80-E (Gasoline)) >> Diagnostic Tests >> DTC P1810: Transmission Fluid Pressure (TFP) Position Switch Malfunction >> Diagnostic Procedures

Diagnostic Procedures

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  1. Check transmission fluid. Fill as needed. Ensure transmission shift linkage is adjusted correctly. 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. Start engine and let idle. Apply parking brake. While observing scan tool, shift transmission into each gear position. If gear position matches Transmission Fluid Pressure (TFP) position switch A/B/C display on scan tool, see DIAGNOSTIC AIDS. See TFP LOGIC TABLE. If gear position does not match Transmission Fluid Pressure (TFP) position switch A/B/C display on scan tool, go to next step.
  3. Turn ignition off. Disconnect transmission 20-pin connector. Install Jumper Harness (J-39775) on VCM side of transmission 20-pin connector. Turn ignition switch to ON position. DO NOT start engine. Using a DVOM, measure voltage at range input circuits "N", "P" and "R" at transmission 20-pin connector. See procedures in WIRING DIAGRAMS . If battery voltage is present at all circuits, go to step 5). If battery voltage is not present at all circuits, go to next step.
  4. Check each circuit which did not have battery voltage for open or short to ground. Repair circuit(s) as necessary, then go to step 6). If all circuits are okay, inspect wiring for poor connections at appropriate VCM connector. Check for bent, backed out, deformed or damaged terminals. Repair as necessary, then go to step 6). If connections and terminals are okay, replace VCM, then go to step 6).
  5. Ensure circuits are not shorted together. Use a fused jumper to separately ground each circuit while monitoring scan tool TFP position switch A/B/C display. Repair circuits as necessary, then go to next step. If all circuits are okay, diagnose Transmission Fluid Pressure (TFP) position switch. Switch is also referred to as Pressure Switch Assembly (PSA). See COMPONENT TESTS .
  6. After repair is complete, select DTC on scan tool. Select "Clear Info" function. Select "Specific DTC" and enter DTC "P1810". Turn ignition switch to ON position for at least 2 seconds. Start vehicle and idle in Park above 600 RPM for 7 seconds. Drive vehicle in "D4" with throttle angle at least 9 percent until TCC locks for one minute. If DTC P1810 is not present, repair is complete. If DTC P1810 is still present, repeat test.
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