1998 Cadillac Eldorado BaseFACTORY OEM SERVICE PROCEDURE

Chart A: Scan Tool Will Not Communicate: Testing

  1. Enter on-board diagnostics. See ENTERING & EXITING DIAGNOSTICS  under SELF-DIAGNOSTIC SYSTEM. If on-board diagnostics can be entered, go to next step. If on-board diagnostics cannot be entered, go to step 3).
  2. Turn ignition switch to OFF position. Disconnect PZM connectors. Using DVOM, check resistance between Data Link Connector (DLC) terminal No. 2 (Purple wire) and PZM Brown 24-pin connector C1, terminal A1 (Purple wire). If resistance is 5 ohms or less, scan tool may be malfunctioning. See scan tool manufacturer's instructions. If resistance is greater than 5 ohms, repair open in Purple wire. See WIRING DIAGRAMS  .
  3. Turn ignition switch to OFF position. Disconnect all modules connected to class 2 serial data line. Using DVOM, check resistance between DLC terminal No. 2 (Purple wire) and ground. If resistance is infinite, go to next step. If resistance is not infinite, repair short to ground in Purple wire. See WIRING DIAGRAMS  .
  4. Turn ignition switch to ON position. Using DVOM, check voltage between DLC terminal No. 2 (Purple wire) and ground. If no voltage exists, go to next step. If any voltage exists, repair short to battery in Purple wire. See WIRING DIAGRAMS  .
  5. Turn ignition switch to OFF position. Reconnect 3 Instrument Panel Cluster (IPC) connectors. Using scan tool, attempt to establish communication with IPC. If communication can be established, go to next step. If communication cannot be established, replace IPC. See INSTRUMENT PANEL article.
  6. Ensure ignition switch is in OFF position. Individually reconnect each module (if equipped) in specified order. Using scan tool, attempt to establish communication with reconnected module. When communication cannot be established, replace most recently connected module. Reconnect modules in the following order:
    • Body Control Module (PZM)
    • Remote Function Actuator (RFA)
    • Instrument Panel Cluster (IPC)
    • Sensing & Diagnostic Module (SDM)
    • Electronic Brake Traction Control Module (EBTCM)
    • Powertrain Control Module (PCM)
    • Heater & A/C Programmer (ACM)
    • Amplifier
    • Electronic Suspension Module
    • Radio (IRC)
    • Memory Seat Module (MSM)
    • Cellular Phone Module (PHN)
    • Memory Mirror Module (MMM)
    • Climate Control Panel (CCP)
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.