01 The Wankel Rotary Engine: Compact, Smooth, and Powerful • 02 Understanding Why Cars Shut Off While Driving and Ensuring … • 03 How to Read & Understand Live Data Streams from Your Car’s … • 04 This Is Why Your Car’s EGR Valve Is Stuck • 05 Hybrid Vehicles: How They Work and Their Pros and Cons • 06 The Hidden Safety Feature In Modern Cars That Most Owners N… • 07 How to Rebuild a Car Battery (Is It Worth the Effort?) • 08 P0042, P0043, and P0044: H02S heater control circuit (Bank … • 09 Engine Oil Leak Areas: Identifying Elusive Culprits • 10 Activists Using Cones to Disable Self-Driving Cars in San F… •

DTC codes / Chrysler codes / P1686

P1686 · ChryslerNo SKIM Bus Message Received

P1686 on Chrysler vehicles means the engine computer (PCM) has not received a valid data message from the Sentry Key Immobilizer Module (SKIM) over the vehicle's internal communication bus. The PCM expects a continuous security handshake from the SKIM, and when that message goes missing, it stores this code and typically prevents the engine from starting or running normally.

SystemPowertrain
Code typeChrysler specific
SeverityHigh
Fix difficultyProfessional
AreaComputer and output circuits

Symptoms you may notice

  • The engine cranks but will not start, or starts and stalls immediately
  • The security light (a key or padlock icon) stays on or flashes after the ignition is turned on
  • The engine may start and run normally on some cycles, then fail to start on the next
  • A no-start condition that occurs more often in cold or damp weather
  • The scan tool cannot communicate with the SKIM module when you try to read its codes
  • Often no symptoms besides the warning light if the fault is intermittent

Common causes, most likely first

  1. A faulty or intermittent connection at the SKIM module connector, often due to corrosion or a loose pin
  2. A damaged or shorted data bus wire between the SKIM and the PCM (the PCI or CAN bus depending on model year)
  3. A failed Sentry Key Immobilizer Module (SKIM) that no longer powers up or communicates
  4. A poor ground or power feed to the SKIM module, causing it to drop offline intermittently
  5. A defective ignition key transponder that the SKIM cannot read, though this usually sets a different code
  6. A faulty PCM that is not listening on the bus, though this is rare compared to SKIM-side faults
  7. Aftermarket remote starters or alarm systems that tap into the bus and disrupt the SKIM message

How to diagnose and fix it

  1. Connect a scan tool and check for communication with the SKIM module; if it does not respond, inspect the SKIM connector and wiring first
  2. Check the SKIM module's power and ground circuits with a multimeter, looking for voltage drops or open circuits
  3. Inspect the data bus wiring between the SKIM and PCM for chafing, corrosion, or loose pins, and repair as needed
  4. Perform a wiggle test on the SKIM connector and harness while watching live data to catch an intermittent fault
  5. If wiring and power are good, substitute a known-good SKIM module and attempt to start the vehicle
  6. If the SKIM is replaced, program the module and all keys to the PCM using a factory-level scan tool
  7. As a last resort, check the PCM for bus communication faults and replace only after confirming the SKIM and wiring are sound

Why the SKIM message goes missing

  • A weak or failing battery can cause the SKIM module to drop offline during cranking, setting P1686 even though the module itself is fine.
  • Aftermarket remote start systems that splice into the bus wiring are a frequent culprit because they can corrupt or interrupt the SKIM handshake.
  • The code can be stored intermittently and clear itself, so a no-start complaint with no current code often requires checking for pending or history codes.
  • A faulty ignition switch can cut power to the SKIM module only in certain key positions, mimicking a failed module.
  • On some Chrysler models, a bad body control module (BCM) can disrupt bus traffic and prevent the SKIM message from reaching the PCM.

Can I keep driving with P1686?

Do not drive the vehicle if it will not start or stalls immediately, because the security system is preventing normal operation. If the engine starts and runs, drive only to a safe location or repair shop, as the fault can cause an unexpected no-start at any time.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage