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DTC P1685: Invalid Skim Key: Testing

  1. Turn ignition on, with engine off. Using scan tool, read DTCs. If DTC SPECIFIC GOOD TRIP counter is displayed and displayed count is "0", go to next step. If DTC SPECIFIC GOOD TRIP counter is not displayed or displayed count is not "0", go to step  6 .
  2. Using scan tool, check for PCM DTCs. If DTC P1687: NO MIC BUS MESSAGE and/or DTC P1698: NO BUS MESSAGE FROM TCM is present, go to next step. If DTC P1687: NO MIC BUS MESSAGE and/or DTC P1698: NO BUS MESSAGE FROM TCM is not present, go to step  7 . If PCM will not read DTCs, go to NO RESPONSE FROM PCM (SCI ONLY)  under SCAN TOOL ERROR MESSAGES. If vehicle will not start, go to ENGINE DOES NOT START & DRB DISPLAYS NO RESPONSE under NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES article.
  3. Using scan tool, select the following control modules and note if they communicate with scan tool. Using scan tool, select BODY then BCM. Using scan tool, select DOOR MODULES. Using scan tool, select ANTI-LOCK BRAKES. Using scan tool, select ELECTRO-MECHANICAL CLUSTER (MIC). Using scan tool, select PASSIVE RESTRAINTS then AIR BAG. If one or more modules communicated with scan tool, go to next step. If no modules communicated with scan tool, go to PCI BUS COMMUNICATION FAILURE under COMMUNICATIONS in BODY CONTROL MODULES - GRAND CHEROKEE article in ACCESSORIES & EQUIPMENT.
  4. Turn ignition off. Disconnect PCM connectors. PCM is located on firewall in right rear corner of engine compartment. Visually inspect connectors for corroded, damaged, pushed-out or miswired terminals. Repair connectors as necessary. If connectors are okay, ensure scan tool is connected to Data Link Connector (DLC). Connect Scope Input Cable (CH7058) to channel one connector on scan tool. Obtain Red and Black test probes from DRB scan tool test kit. Connect Red and Black test probe leads to Probe Adapter (CH7062). Connect probe adapter to scope input cable. Using scan tool, select DRB STANDALONE, LAB SCOPE, LIVE, then 12 VOLT SQUARE WAVE. Using scan tool, press F2 for scope. Press F2 again and arrow down until 20 volt scale is selected. Press F2 again when complete. Connect Black test probe to ground and Red test probe to terminal No. 30 (Yellow/Violet wire) at PCM C3 connector. See Figure . Turn ignition on and observe voltage displayed on DRB lab scope. If voltage pulses from zero volts to about 7.5 volts, go to next step. If voltage is a constant zero volts, repair open PCI bus circuit (Yellow/Violet wire). See WIRING DIAGRAMS article.
  5. PCM has an internal open PCI bus circuit. Replace PCM.
  6. DTC P1685 may have been set if Sentry Key Immobilizer Module (SKIM) was disconnected or recently replaced. All of the customer ignition keys for this vehicle must be tested at this time. Turn ignition off and remove ignition key. Using another customer key, turn ignition on and attempt to start engine. If engine starts, this usually indicates a good key. Continue using remaining ignition keys. Using scan tool, check for DTCs. If DTC SPECIFIC GOOD TRIP counter is displayed and displayed count is "0", go to next step. If DTC SPECIFIC GOOD TRIP counter is not displayed or displayed count is not "0", no problem is indicated at this time. Test is complete. DTC may have been set by an actual theft attempt.
  7. Using scan tool, select THEFT ALARM, then SKIM. If SKIM communicates with scan tool, go to next step. If SKIM does not communicate with scan tool, go to BUS +/- SIGNALS OPEN FROM SENTRY KEY IMMOBILIZER MODULE (SKIM) under COMMUNICATIONS in BODY CONTROL MODULES - GRAND CHEROKEE article in ACCESSORIES & EQUIPMENT.
  8. Turn ignition on. Using scan tool, select THEFT ALARM, SKIM and then MISCELLANEOUS. To perform some of the following functions, it may be necessary to have Personal Identification Number (PIN) for this vehicle. PIN may be obtained from the owner, vehicle's invoice, or from the manufacturer. Verify correct Vehicle Identification Number (VIN) is in both the PCM and SKIM modules. Select action according to what module needs to be updated. Follow scan tool instructions until procedure is complete. Try all keys to ensure each key will start vehicle. At this time, SKIM key data should be updated. Using scan tool, clear DTCs.
    NOTE: For additional information on programming, see PROGRAMMING  .
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