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Home >> Ford >> 1996 >> Aerostar Van Window >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Automatic Transmission - Diagnosis - 4R44E & 4R55E Automatic Transmission >> EEC-V Circuit Tests >> Circuit Test Tb - Trans. Control Switch (TCS) & Trans. Control Indicator Lamp (TCIL) >> Diagnostic Aids

Diagnostic Aids

Perform this test when instructed during QUICK TEST or if directed by other test procedures. This test is used to diagnose the following:

Fig 1: TCIL & TCS Circuit Schematic
G96I01051
  1. 1) Check Test Validity  DTC P1780 indicates that TCS was not cycled during KOER self-test. Possible causes are as follows:
    • TCS not cycled during KOER self-test.
    • TCS circuit faulty.
    • Faulty TCS.
    • Faulty Powertrain Control Module (PCM).

    Repeat KOER self-test if TCS was not cycled in original test. If TCS was cycled during KOER self-test, go to next step.

  2. 2) Check TCS Circuit Voltage  Turn ignition off. Disconnect PCM connector. Inspect pins for damage. Install breakout box, leaving PCM disconnected. Turn ignition on. Measure voltage between test pin No. 29 (TCS) and test pins No. 24 and 77 (PWR GND) at breakout box while cycling TCS. If voltmeter reading does not cycle when TCS is cycled, go to next step. If voltmeter reading cycles when TCS is cycled, replace PCM. Remove breakout box and repeat QUICK TEST.
  3. 3) Check TCS Circuit For Short To Ground  Turn ignition off. Disconnect TCS. Inspect pins for damage and repair if necessary. Measure resistance between test pin No. 29 (TCS) and test pins No. 24 and 77 (PWR GND). If resistance is 10 k/ohms or more, go to next step. If resistance is less than 10 k/ohms, repair short circuit. Remove breakout box and repeat QUICK TEST.
  4. 4) Check TCS Circuit Continuity  Leave ignition off. Connect ohmmeter positive lead to TCS keypower at the fuse panel. Connect negative lead to power terminal of TCS wiring harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit. Remove breakout box and repeat QUICK TEST.
  5. 5) Check TCS Circuit For Short To Power  Leave ignition off. Measure resistance between test pin No. 29 (TCS) and test pins No. 71 and 97 (VPWR). If resistance is 10 k/ohms or more, replace TCS switch. Remove breakout box and repeat QUICK TEST. If resistance is less than 10 k/ohms, repair short circuit. Remove breakout box and repeat QUICK TEST.
  6. 6) TCIL Always On  Turn ignition on. Cycle TCS. If TCIL does not cycle on and off, go to next step. If TCIL cycles on and off, fault may be intermittent. Connect scan tool to DLC. Access TCS PID. Perform wiggle test of TCS/TCIL circuit harness and connectors while observing scan tool. If TCS PID changes abruptly, inspect and repair circuits or replace components as needed. Clear continuous memory and repeat QUICK TEST.
  7. 7) Check TCIL Circuit For Short To Ground  Turn ignition off. Disconnect PCM connector. Inspect pins for damage and repair if necessary. Turn ignition on. If TCIL is off, replace PCM. If TCIL remains on, repair TCIL circuit short to ground.
  8. 8) TCIL Will Not Turn On  Perform KOER self-test. If DTC 1780 is not present, go to next step. If DTC 1780 is present, go to step 1).
  9. 9) Check Circuit For Continuity  Disconnect PCM connector. Inspect pins for damage and repair if necessary. Turn ignition on. Measure voltage between test pin No. 79 (TCIL) and test pins No. 24 and 76 (PWR GND) at breakout box. If voltage is 2 volts or more, replace PCM. If voltage is less than 2 volts, check indicator bulb and fuse. If bulb and fuse are okay, repair open circuit between test pin No. 79 and ignition switch.
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