Battery was disconnected or replaced during recent service, which is the normal and most common trigger.; Loose, corroded, or poorly tightened battery terminal clamps causing an intermittent voltage drop.; Failing battery that drops below the PCM's keep-alive threshold during cranking or while parked.; Corroded or chafed battery positive and ground cables, including the engine-to-body ground strap.; Blown or intermittent fuse in the PCM's constant battery feed circuit, often caused by a shorted accessory.; Aftermarket alarm, remote starter, or audio installation that interrupts the PCM's constant power.; A failing PCM that loses its keep-alive memory even with a healthy battery and clean connections.

DTC codes / Chrysler codes / P1684

P1684 · ChryslerBattery Disconnected Within Last 50 Starts

Q: What does code P1684 mean?

Battery Disconnected Within Last 50 Starts. P1684 is a Chrysler-specific informational code that the powertrain control module (PCM) sets when it detects that the battery has been disconnected or its power feed was interrupted within the last 50 ignition cycles. The PCM logs this event because it loses its learned adaptive memory and idle strategy whenever battery voltage is removed, and it counts each subsequent start until the 50-start window clears the code.

P1684 is a Chrysler-specific informational code that the powertrain control module (PCM) sets when it detects that the battery has been disconnected or its power feed was interrupted within the last 50 ignition cycles. The PCM logs this event because it loses its learned adaptive memory and idle strategy whenever battery voltage is removed, and it counts each subsequent start until the 50-start window clears the code.

SystemPowertrain

Code typeChrysler specific

SeverityLow

Fix difficultyDIY

AreaComputer and output circuits

Symptoms you may notice

Often no symptoms besides the warning light, because the code is purely informational.
Rough or erratic idle for the first few minutes after reconnecting the battery, as the PCM relearns fuel trim and idle position.
Transmission may shift more firmly or hold gears longer during the relearn period on models with adaptive shift logic.
Radio station presets, clock, and other memory settings reset if the battery was actually disconnected.
A stored P1684 that keeps returning even though you never touched the battery, pointing to an intermittent power loss.
No drivability complaint at all in most cases, with the code clearing itself after 50 clean start cycles.

Common causes, most likely first

Battery was disconnected or replaced during recent service, which is the normal and most common trigger.
Loose, corroded, or poorly tightened battery terminal clamps causing an intermittent voltage drop.
Failing battery that drops below the PCM's keep-alive threshold during cranking or while parked.
Corroded or chafed battery positive and ground cables, including the engine-to-body ground strap.
Blown or intermittent fuse in the PCM's constant battery feed circuit, often caused by a shorted accessory.
Aftermarket alarm, remote starter, or audio installation that interrupts the PCM's constant power.
A failing PCM that loses its keep-alive memory even with a healthy battery and clean connections.

How to diagnose and fix it

Verify the battery state of charge and perform a load test; replace the battery if it fails.
Inspect and clean both battery terminals and the engine-to-body ground strap, then tighten to specification.
Check the PCM constant battery feed fuse and inspect the wiring for corrosion or chafing.
Ask the customer or check service records for a recent battery replacement or disconnect, which explains the code.
Clear the code with a scan tool and drive the vehicle through several start cycles to confirm it does not return.
If the code returns without any battery work, perform a voltage drop test on the battery cables and PCM feed circuit.
As a last resort, test the PCM keep-alive memory circuit and replace the PCM only if it cannot hold memory with a known-good battery.

What P1684 really tells you about battery power

P1684 is one of the few codes that can be set by normal service work, so a recent battery replacement or disconnect is the first thing to confirm before any diagnosis.
The code does not mean the battery is currently bad; it only records that power was interrupted, and it will clear itself after 50 ignition cycles if the cause was a one-time event.
A loose ground strap or corroded terminal can drop voltage just long enough to set P1684 without ever causing a no-start, which is why voltage drop testing matters more than a simple voltage reading.
Aftermarket electronics that tap into the PCM's constant power circuit are a commonly missed cause, especially on trucks and SUVs with added accessories.
Do not replace the PCM for P1684 until you have proven the battery, cables, and fuses are good, because a healthy PCM will set this code any time its keep-alive power is interrupted.

Can I keep driving with P1684?

It is safe to keep driving with P1684 because the code is informational and does not indicate a current failure, but address any loose battery connections promptly to avoid a no-start or other electrical faults. Avoid ignoring repeated P1684 codes, since they can point to a failing battery or cable that will eventually leave you stranded.

Tools that help

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