2003 Jeep Wrangler X, AutomaticFACTORY OEM SERVICE PROCEDURE

P1698-No Bus Message From Trans Control Module: Testing

  1. With the ignition on and the engine not running, erase the DTCs with the DRBIII®. Cycle the ignition key on and off several times. With the DRBIII®, read DTCs. Does the DTC reset? If yes, go to the next step. If no, refer to the INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM. Perform POWERTRAIN VERIFICATION TEST VER-1 .
    NOTE: This DTC could have been set when the TCM was disconnected during transmission Diagnostics.
    2. NOTE: This test checks for other PCI BUS codes. That indicates different circuits in the BUS.
  2. With the ignition on and the engine not running, connect the DRBIII® and access Powertrain Control Module. Read the DTCs. Is a DTC also set for NO SKIM BUS MESSAGE and/or No MIC BUS MESSAGE? If yes, go to the next step. If no, refer to the Communication Category and perform the appropriate symptom related to the no communication with TCM. Perform POWERTRAIN VERIFICATION TEST VER-1 .
    3. NOTE: If the DRBIII® will not read PCM DTC's, perform "NO RESPONSE TO PCM (SCI only)" under COMMUNICATIONS under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT, if vehicle will start. For no-start conditions see NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES article.
  3. With the DRBIII®, read DTCs. This is to ensure power and grounds to the PCM are operational. Turn the ignition off. Disconnect the PCM harness connector(s). Connect the DRBIII® to the Data Link connector. Use Scope input cable CH7058, Cable to Probe adapter CH7062, and the Red and Black test probes. Connect the scope input cable to the channel one connector on the DRBIII®. Attach the Red and Black leads and the cable to probe adapter to the scope input cable. Select DRBIII® Stand-alone. Select lab scope. Select Live. Select 12 volt square wave. Press F2 for Scope. Press F2 and use the down arrow to set voltage range to 20 volts. Press F2 again when complete. Connect the Black lead to the PCM ground. Connect the Red lead to the PCM PCI Bus circuit Ignition on, engine not running. Observe the voltage displayed on the DRBIII® Lab Scope. What is the voltage displayed on the scope? If it's a pulse from 0 to approximately 7.5 volts, the test is complete. If it's a steady 0 volts, repair the open PCI Bus circuit to PCM and perform POWERTRAIN VERIFICATION TEST VER-1 .
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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.

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