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DTC codes / Chrysler codes / P1388

P1388 · ChryslerAuto Shutdown (ASD) Relay Control Circuit Open Or Shorted

P1388 on Chrysler vehicles means the powertrain control module (PCM) has detected an open or shorted condition in the control circuit for the Auto Shutdown (ASD) relay, which supplies power to the ignition coil, fuel injectors, and fuel pump. The PCM monitors the ASD relay control wire and sets this code when the voltage on that circuit falls outside the expected range during a self-test or normal operation.

SystemPowertrain
Code typeChrysler specific
SeverityHigh
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Engine cranks but does not start because the ASD relay never energizes the fuel and ignition circuits
  • Engine stalls intermittently or shuts off while driving, especially over bumps or when hot
  • No fuel pump prime sound when the key is turned to the run position
  • No spark at the spark plugs during a crank test
  • Often no symptoms besides the warning light if the fault is intermittent and the relay still closes
  • Other codes for injector or ignition coil circuits may appear because those components lose power

Common causes, most likely first

  1. Open or shorted wire in the ASD relay control circuit between the PCM and the relay coil
  2. Failed ASD relay itself, with burned contacts or an open coil winding
  3. Corroded or loose terminals at the ASD relay socket or the PCM connector
  4. Blown fuse in the ASD relay feed circuit, often caused by a shorted oxygen sensor heater or injector
  5. Faulty PCM driver for the ASD relay control circuit, though this is less common
  6. Chafed harness rubbing against a bracket or passing through a tight grommet

How to diagnose and fix it

  1. Check the ASD relay fuse and replace it if blown, then inspect the relay socket for corrosion
  2. Swap the ASD relay with an identical known-good relay from the same fuse box and clear the code to see if it returns
  3. Use a wiring diagram to locate the ASD relay control wire and check for continuity and short-to-ground between the PCM and the relay
  4. Inspect the harness for chafing, especially near the engine block and under the fuse box, and repair any damaged insulation
  5. Check the PCM connector pins for tightness and corrosion, then perform a wiggle test on the harness while watching live data
  6. If the circuit and relay test good, test the PCM driver with a noid light or oscilloscope and replace the PCM only if the driver is confirmed faulty

What the ASD relay really controls

  • The ASD relay does not just feed the fuel pump; it also powers the ignition coil and injectors, so a failed relay can cause a no-start with no fuel pump prime and no spark at the same time.
  • A shorted oxygen sensor heater or a shorted injector can blow the ASD fuse and set P1388, so always check those circuits before replacing the relay or PCM.
  • Intermittent P1388 codes often come from a relay that tests fine on the bench but drops out when hot, so a heat gun test on the relay can reveal the fault.
  • Chrysler PCMs rarely fail on the ASD driver, but a poor ground at the PCM case can mimic a failed driver and cause repeated relay failures.
  • The ASD relay control circuit is monitored only when the PCM commands the relay on, so a code can set during a key-on self-test even if the engine starts normally afterward.

Can I keep driving with P1388?

Do not drive the vehicle with an active P1388 because the engine can stall without warning and leave you stranded in traffic. If the code is intermittent and the engine runs normally, drive only to a safe repair location and avoid heavy traffic or high-speed roads.

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.

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