P0604 on 2017-2024 Chrysler Pacifica: RAM Error Causes and Fixes

What's Unique About the 2017-2024 Chrysler PACIFICA

On the Chrysler Pacifica, this code is specifically mentioned in Technical Service Bulletin (TSB) #18-044-26 alongside other internal processor faults. This indicates that Chrysler has recognized a pattern of these codes, which are often resolved with a PCM software update rather than an immediate hardware replacement. This makes a dealer-level software reflash a primary diagnostic step, not a last resort. Multiple TSBs for related platforms confirm that maintaining stable battery voltage (13.2V-13.5V) during the flash is critical to avoid damaging the PCM.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• Engine may stall or shut off unexpectedly
• Hard-start or no-start condition, may not crank
• Harsh or erratic transmission shifting
• Vehicle may enter a reduced power "limp mode"
• Multiple other warning lights (ABS, Traction Control) may illuminate
• Brake pedal may be hard to push during a no-start event

Most Likely Causes

1. PCM Software Glitch / Update Required 🔴 High Probability As referenced in TSBs for the Pacifica and its platform mates, the PCM software can develop glitches that are resolved with updated programming from the manufacturer.
   How to confirm: A dealership or a well-equipped independent shop can use a scan tool (wiTECH) to check the current software calibration ID against the latest available version from Chrysler for your vehicle's VIN.
   Typical fix: Reprogramming (reflashing) the PCM with the latest software. This is a software-only repair and often requires updating other modules like the TCM at the same time.
   Est. part cost: $0
2. Weak or Failing 12V Battery 🟡 Medium Probability Modern vehicles like the Pacifica are packed with electronics. Low voltage during startup or from a failing battery can cause modules to perform self-checks improperly, leading to erroneous memory fault codes.
   How to confirm: Test the battery with a digital multimeter or a professional battery tester. A healthy, resting battery should be above 12.4 volts. Check the voltage during cranking; it should not drop below 9.6-10.0 volts. Forum users frequently report that seemingly good batteries were the ultimate cause.
   Typical fix: Charge or replace the 12V battery. Ensure battery terminals are clean and tight.
   Est. part cost: $150-$350
3. Defective Powertrain Control Module (PCM) ⚪ Low Probability While less common than software or battery issues, the internal hardware of the PCM can fail over time due to heat, vibration, or voltage spikes.
   How to confirm: This is a process of elimination. If the battery is good, the software is up-to-date, and all power/ground connections to the PCM are verified with a voltage drop test, the module itself is the likely culprit.
   Typical fix: Replace the PCM and program the new unit to the vehicle's VIN and configuration. This must be done by a dealer or a specialist with proper tools.
   Est. part cost: $500-$1500
4. Poor Power or Ground Connection to PCM ⚪ Low Probability Corrosion or looseness at the PCM connectors or main chassis grounds can cause intermittent voltage drops, confusing the module and triggering memory faults. Owners on Chrysler forums have traced similar no-start electrical issues to bad ground wires.
   How to confirm: Visually inspect the PCM connectors for corrosion or backed-out pins. Perform a voltage drop test on the PCM's power and ground circuits; resistance should be below 0.1 Ω.
   Typical fix: Clean and secure the ground connections (e.g., engine block to chassis). Clean the PCM connector pins. Repair any damaged wiring.
   Est. part cost: $0-$100

Rare But Worth Checking

• Aftermarket Performance Tune: If the vehicle has an aftermarket engine tune, it can corrupt the PCM's memory or cause conflicts. Reverting to the factory software is a critical diagnostic step.
• Failing Alternator: An alternator producing excessive AC ripple or unstable voltage (over 15V) can damage sensitive electronics, including the PCM's RAM, or trigger faults.

Diagnosis Steps

1. Check Battery Health: Fully charge and test the 12V battery. Ensure terminals are clean and tight. A weak battery is a common cause.
2. Scan for All Codes: Use a professional scan tool to read 🎬 Watch: How to connect the 12+8 adapter for scanning. all codes from all modules, not just the engine.
3. Check for TSBs and Software Updates: This is the most critical step. Have a dealer or qualified shop check if a PCM software update is available for your Pacifica's VIN. The reflash procedure requires a stable power supply between 13.2 and 13.5 volts.
4. Inspect PCM Connections: Visually inspect the wiring harness and connectors at the PCM for any signs of damage, corrosion, or loose pins.
5. Verify Power and Grounds: If the problem persists, perform a voltage drop test on the PCM's power and ground circuits to ensure it's receiving stable voltage. Voltage should remain above 9V during cranking, and ground resistance should be under 0.1 Ω.
6. PCM Replacement: If all other steps fail, the PCM is likely faulty. It requires replacement and programming with a VIN-matched unit.

Parts You'll Likely Need

• Powertrain Control Module (PCM) (OEM #68330910AA, 68434928AC (Varies by VIN and model year)) — If software updates and power checks fail, the internal RAM hardware has likely failed, requiring module replacement.
  Trusted brands: Mopar (OEM)
  OEM price range: $800-$1500
  Aftermarket price range: $500-$1000
• 12V Automotive Battery — Low or unstable voltage from a failing battery is a frequent trigger for this memory fault code.
  Trusted brands: Interstate, DieHard, Duralast
  OEM price range: $250-$400
  Aftermarket price range: $150-$350

Related Codes That Often Appear With This One

• P060C — Mentioned in the same TSB (#18-044-26) as P0604, this code relates to 'Internal Control Module Main Processor Performance', reinforcing that the issue is internal to the PCM.
• P062B — Also listed in TSB #18-044-26, this code for 'Internal Control Module Fuel Injector Control Performance' points to another internal PCM self-check failure.
• P0602 — This code means 'Control Module Programming Error'. It can appear with P0604 after a failed reflash attempt or if the PCM's programming has become corrupted.
• P0456 — This 'Evap System Small Leak' code is mentioned in other Chrysler PCM update TSBs (like 18-001-19 REV. B), indicating that software updates often address multiple unrelated-seeming codes at once.

Technical Service Bulletins (TSBs) & Recalls

• 18-044-26: Addresses a cluster of internal PCM fault codes, including P0604, that may be resolved with a software update for 2017 models.
• 18-001-19 REV. B: A separate TSB for 2018 models that involves a PCM reflash to fix numerous DTCs, a highlighting the commonality of software-based repairs.
• General Flashing Procedure Notes: Multiple Chrysler TSBs emphasize the need to connect a battery charger and maintain voltage between 13.2 and 13.5 volts during any reprogramming to prevent PCM failure.

Platform-Specific Known Issues

• Chrysler TSB #18-044-26 explicitly lists P0604-00 ('Internal Control Module Random Access Memory Ram Error') as a potential fault code that may be addressed by a PCM software update on 2017 models.
• Other PCM software update TSBs, like 18-001-19 REV. B for 2018 models, address a wide range of electrical gremlins and DTCs, showing a pattern of software fixes for this platform.

Mechanic-Grade Diagnostic Values

• CAN C Bus Voltage (at OBD-II port pins 6 & 14) — expected: A stable 2.5 volts on both CAN High and CAN Low lines when the bus is idle.. Failure: A sawtooth pattern or voltage spikes, for example up to 3.5V, indicate noise or a module issue on the network.
• Alternator Output Voltage (at battery terminals, engine running) — expected: Stable voltage between 13.5V and 14.8V.. Failure: Voltage that is too low, too high (over 15V), or fluctuating wildly can corrupt module memory.
• PCM Power and Ground Circuit Testing — expected: Use of Miller Special Tool #8815 is specified to avoid damaging terminals.. Failure: Do not probe PCM harness connectors directly with multimeter leads, as this can damage the terminals and lead to poor connections.

Scan Tool Commands That Help

• Aftermarket Scan Tool (Autel, Launch, etc.): 12+8 Secure Gateway (SGW) Adapter Connection — Required on all 2017+ Pacifica models to perform any bidirectional control, such as resets, programming, or actuations. The adapter bypasses the SGW and connects behind the center infotainment/shifter panel.
• wiTECH 2.0 (Dealer Tool): PCM Flash / Reprogramming — Used to install updated software from Chrysler to fix bugs that can cause P0604. This process requires a stable battery charger/power supply to be connected to the vehicle to prevent voltage drops that could 'brick' the PCM.

Wiring & Ground Locations

• CAN-C Bus Star Connector — Located under the passenger side glove box area. It is a small box where multiple pairs of CAN bus wires converge.. This is a central hub for high-speed communication. Poor pin retention or corrosion in this single connector can cause a loss of communication between the PCM, TCM, ABS, and other critical modules, often generating a flood of U-codes alongside internal faults like P0604. It is a known failure point that can mimic a bad PCM.

Real Owner Repair Stories

• BL Automotive, YouTube (2017 Chrysler Pacifica) — Vehicle would not shift, electronic power steering would go out, and a flood of communication (U-codes) were present across multiple modules (PCM, TCM, ABS, BCM). The issue was intermittent.
  ❌ Tried (didn't work) Previous shops had been unable to diagnose the issue, likely because they were using multimeters instead of an oscilloscope and were not able to reproduce the fault.
  ✅ What actually fixed it Using an oscilloscope, the technician found a noisy, corrupted sawtooth pattern on the CAN bus. The fault was traced to poor pin retention in the CAN-C bus star connector under the glove box. Replacing the star connector and the female pin terminals in the harness connectors resolved the communication faults.

OEM Part Supersession History

• 68434928AA, 68434928AB → 68434928AC — Part revision and updates by manufacturer.
  Heads up: The last two letters (e.g., AA, AB, AC) typically refer to the manufacturing date or revision and are generally interchangeable, with the latest version being preferred.

Model Year Variations Within This Range

• 2017+: All models from 2017 onward are equipped with a Secure Gateway Module (SGW). This requires a special '12+8 adapter' cable for any aftermarket scan tool to perform bidirectional functions (like resets or relearns). The connection point is behind the center stack panel, not at the standard OBD-II port.
• 2017 vs 2018+: The primary PCM part numbers appear to change. 2017 models often use a part number beginning with 6833xxxxxx, while 2018 and newer models use part numbers like 68434928xx. Always verify the correct part number by VIN.
• 2021+: The 2021 model year refresh introduced significant electronic changes, including the Uconnect 5 infotainment system on a larger 10.1-inch screen and standard advanced safety features. While not directly tied to P0604, these changes mean wiring diagrams and module interactions may differ from earlier 2017-2020 models.