2002 Jeep Liberty Limited, RWDFACTORY OEM SERVICE PROCEDURE

DTC P1698: No Bus Message From Trans Control Module: Testing

  1. Turn ignition on, engine not running. With the DRBIII®, erase DTCs. Cycle the ignition key on and off several times. With the DRBIII®, read DTCs. Does the DTC reset? If yes, go to next step. If no, go to step  4.
  2. Connect the DRBIII® and access PCM. This test checks for other PCI bus codes. With the DRBIII®, read DTCs. Is a DTC also set for NO SKIM BUS MESSAGE and/or NO MIC BUS MESSAGE? If yes, go to next step. If no, perform appropriate test for no communication with TCM. See COMMUNICATIONS under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
    3. NOTE: If the DRBIII® will not read PCM DTCs and vehicle will not start, see NO RESPONSE FROM PCM (SCI ONLY) in COMMUNICATIONS under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If vehicle will start, see NO RESPONSE FROM PCM WITH A NO-START CONDITION under 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 connectors. 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® Standalone. 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 at the PCM harness connector. Connect the Red lead to the PCM PCI Bus circuit at the PCM harness connector. Turn ignition on, engine not running. Observe the voltage displayed on the DRBIII® Lab Scope. What is the voltage displayed on the scope? If voltage pulsed from 0 to approximately 7.5 volts, test is complete. If voltage is steady 0 volts, repair the open PCI Bus circuit to PCM.
  4. Turn ignition off. Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect the related wire harness connectors. Look for broken, bent, pushed out, or corroded terminals. Refer to any Technical Service Bulletins (TSB) that may apply. Were any problems found? If yes, repair wiring harness/connectors as necessary. If no, test is complete.
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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.

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