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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 68 (Automatic Transmission Diagnosis - 4L80-E (Gasoline)) >> Diagnostic Tests >> DTC P1810: TFP Manual Valve Position Switch Assembly - Circuit Malfunction >> Diagnostic Procedure

Diagnostic Procedure

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  1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Perform the transmission fluid checking procedure. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Was the fluid checking procedure performed? If so, go to next step. If not, see appropriate AUTOMATIC article in TRANSMISSION SERVICING.
  3. Install a scan tool. Turn ignition on, engine off. Before clearing the DTCs, use the scan tool to record the freeze frame and failure records. Using the CLEAR INFO function erases the freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Start the engine and idle at normal operating temperature. Apply the brake pedal. Select each transmission range. Does each selected transmission range match the scan tool TFP SWITCH A/B/C display? See TRANSMISSION FLUID PRESSURE MANUAL VALVE POSITION SWITCH LOGIC  table. If so, see DIAGNOSTIC AIDS  . If not, go to next step.
  4. Inspect the transmission linkage from the gear shift lever to the manual valve for proper adjustment. Adjust the linkage as necessary. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Did the linkage require adjustment? If so, go to step  10 . If not, go to next step.
  5. Turn ignition off. Disconnect the transmission in-line 20-way connector. Additional DTCs may set. Turn ignition on, engine off. Does the scan tool TFP SWITCH A/B/C parameter indicate "HI" for all range signal states? If so, go to next step. If not, go to step  10 .
  6. Turn ignition off. Install the Jumper Harness (J 44152) on the engine side of the transmission in-line 20-way harness connector. Turn ignition on, engine off. Using a DVOM and the Connector Test Adapter Kit (J 35616-A), measure the voltage from jumper harness terminal "N" to ground. Measure the voltage from jumper harness terminal "R" to ground. Measure the voltage from jumper harness terminal "P" to ground. Does the voltage measure ignition voltage at all 3 terminals? If so, go to next step. If not, go to step  11 .
  7. Connect a fused jumper wire from terminal jumper harness "N" (signal circuit "A") to ground while monitoring the scan tool TFP SWITCH A/B/C parameter. When TFP manual valve position switch signal "A" circuit (1224) is grounded, do any other signal circuits indicate LOW? If so, go to step  12 . If not, go to next step.
  8. Connect a fused jumper wire from jumper harness terminal "R" (signal circuit "B") to ground while monitoring the scan tool TFP SWITCH A/B/C parameter. When TFP manual valve position switch signal "B" circuit (1225) is grounded, do any other signal circuits indicate LOW? If so, go to step  12 . If not, go to next step.
  9. Connect a fused jumper wire from jumper harness terminal "P" (signal circuit "C") to ground while monitoring the scan tool TFP SWITCH A/B/C parameter. When TFP manual valve position switch signal "C" circuit (1226) is grounded, do any other signal circuits indicate LOW? If so, go to step  12 . If not, go to step  13 .
  10. Test the TFP manual valve position switch signal "A", signal "B", and signal "C" circuits (1224, 1225 and 1226) that did not indicate HI for a short to ground between the PCM connectors C1, C2 and the transmission in-line 20-way harness connector. Did you find and correct the condition? If so, go to step  17 . If not, go to step  16 .
  11. Test the TFP manual valve position switch signal "A", signal "B" and signal "C" circuits (1224, 1225 and 1226) that did not indicate ignition voltage for an open between the PCM connectors C1, C2 and the transmission in-line 20-way harness connector. Did you find and correct the condition? If so, go to step  17 . If not, go to step  16 .
  12. Test the affected signal circuits of the TFP manual valve position switch for a shorted together condition between the PCM connectors C1, C2 and the transmission in-line 20-way harness connector. Did you find and correct the condition? If so, go to step  17 . If not, go to step  16 .
  13. Test the TFP manual valve position switch signal "A", signal "B" and signal "C" circuits (1224, 1225 and 1226) for an open or shorted condition between the TFP manual valve position switch and the transmission in-line 20-way harness connector. Did you find a condition? If so, go to next step. If not, go to step  15 .
  14. Replace the transmission internal wiring harness assembly. See TRANSMISSION INTERNAL WIRING HARNESS  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17 .
  15. Replace the TFP manual valve position switch. See TRANSMISSION FLUID PRESSURE MANUAL VALVE POSITION SWITCH  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17 .
  16. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  17. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Turn ignition on, engine off for at least 2 seconds.
    • Start the vehicle.
    • Idle the vehicle in Park above 600 RPM for 7 seconds.
    • Drive the vehicle in D4 with the throttle at least 10 percent and the TCC locked for 60 seconds.
    • Select SPECIFIC DTC.
    • Enter DTC P1810.

    Has the test run and passed? If so, system is okay. If not, go to step  1 .

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