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Home >> Cadillac >> 1983 >> Seville 4.1 8 >> Repair and Diagnosis >> Engine Performance >> System >> DFI Tests W/Codes >> Diagnostic Code Charts >> Code 39 - TCC Problem >> Diagnostic Aids

Diagnostic Aids

NOTE: The following procedure is designed to account for intermittent codes. If no malfunction is uncovered using this procedure, it will indicate that the DFI system is OK at this time. Refer to NOTE ON INTERMITTENTS if further investigation is necessary.

The ECM completes the circuit for the TCC solenoid by grounding circuit 422. Grounding this circuit allows the solenoid to energize and supply oil pressure to the torque converter clutch.

Code 39 indicates that the ECM is seeing the engine speed at a greater RPM than would be expected at 55 MPH with the TCC engaged. Possible causes of this condition are:

  1. To begin diagnosis connect a test light to circuit 422 on the ALDL diagnostic connector (pin F). With the TCC disengaged (ECM not grounding circuit 422) the test light should see 12 volts and light.
  2. If the test light lights, then power is being supplied through the TCC brake switch. While in output cycling, circuit 422 should go between 12 volts and 0 volts every 3 seconds. If the test light does not flash the transmission should be checked for a shorted circuit. If the resistance between pins A and D is less than 15 ohms. The solenoid or the wires are shorted and should be repaired. This low resistance through the transmission may have damaged the ECM, therefore, after repairs have been made, check the output of the ECM in output cycling. If the resistance is greater than 15 ohms, then circuit 422 should be checked for an open to the ECM. If the wire is OK, check for a faulty ECM connector or faulty ECM.
  3. If the test-light goes on and off every 3 seconds, then the ECM and wiring is OK. The fault could be a mechanical problem in the transmission, therefore a road test should be performed. At 55 MPH with the TCC solenoid energized (test-light off), the engine RPM is a factor of the driveline gear ratio if the TCC is working properly. At 55 MPH, engine data parameter .1.1 (engine speed) should read:
    ENGINE DATA PARAMETER

    Vehicle Low & All Altitude High Altitude Only
    Eldorado/Seville 1600 RPM 1700 RPM
    DeVille/Brougham 1700 RPM 1850 RPM

    If the RPM reading is greater than this limit, the TCC has failed to engage and should be diagnosed by referring to appropriate section.

  4. If the test light does not light on circuit 422, then there must be an open between the ALDL connector and the battery. First check the TCC brake switch for proper operation. If there is not voltage on both sides of the connector either the switch or the circuit feeding the switch is open.
  5. If there is voltage on both sides of the TCC brake switch, then the voltage on circuit 420 should be checked at the transmission. If the test light does not light, circuit 420 is open If the test/light between circuits 420 and 422 does not light with Pin F jumpered to ground, then circuit 422 is open. If the test/light does light then the open must exist either at the transmission connector terminals or within the transmission itself.
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