P0604 on 2014-2020 Ram 2500: Internal RAM Error Causes and Fixes

What's Unique About the 2014-2020 Ram 2500

For the 2014-2020 Ram 2500, particularly those with the 6.7L Cummins diesel, this code is uniquely tied to a series of software updates issued by Ram. Multiple Technical Service Bulletins (TSBs) show that P0604 was often triggered as a side effect of software glitches related to the emissions system or other vehicle features, like enabling the remote throttle. As a result, the most common and well-documented fix is not a hardware replacement but a software reflash at a dealership to correct these underlying issues.

Diagnostic Flowchart

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

Generation note: This range covers the fourth generation (2014-2018) and the early fifth generation (2019-2020) Ram 2500. The code's meaning is the same across both, but software updates and PCM part numbers may differ. The issue of software updates correcting this code is well-documented for both generations.

Symptoms You May Notice

• Check Engine Light is on
• Vehicle may not start or may be hard to start
• Engine may stall intermittently or die unexpectedly
• Harsh or erratic transmission shifting
• Reduced engine power or entering "limp mode"
• "Service Electronic Throttle Control" message may appear in the instrument cluster, especially on Cummins models
• ABS or Traction Control lights may illuminate

Most Likely Causes

1. Outdated Powertrain Control Module (PCM) Software 🔴 High Probability → Shop Engine Control Module (ECM) Ram has issued multiple TSBs for the 6.7L Cummins and 6.4L Hemi to address P0604 and other issues via software updates. TSB 18-002-14 REV. B explicitly notes that P0604 can be caused by enabling the remote throttle feature and is fixed by an update. These updates often bundle fixes for emissions codes like P20EE.
   How to confirm: A Ram dealership or a qualified shop with access to OEM software (like wiTECH) can check if your vehicle's VIN has an available PCM software update by comparing the current calibration ID to the latest version.
   Typical fix: Reprogramming (flashing) the PCM with the latest manufacturer software. This is a dealer or specialist repair that typically costs one hour of labor ($150-$275).
   Est. part cost: $0
2. Low Battery Voltage or Weak/Failing Batteries 🟡 Medium Probability → Shop Vehicle Battery Control modules are highly sensitive to voltage. Cummins-equipped trucks have a dual-battery setup, and the high electrical demand during grid heater cycles and cranking can cause a voltage drop sufficient to corrupt the PCM's RAM self-test. If one battery is weak, it can draw down the healthy one.
   How to confirm: Test both batteries individually with a digital load tester. Voltage should be above 12.4V with the engine off and not drop below 9.6V during cranking. With the engine running, alternator output should be stable between 13.5V and 14.8V.
   Typical fix: Replace weak batteries (always in pairs for diesel models) and ensure all battery terminals and ground straps are clean and tight.
   Est. part cost: $250-$500
3. Failing Powertrain Control Module (PCM) ⚪ Low Probability → Shop Engine Control Module (ECM) While less common than software or voltage issues, the PCM can fail internally due to heat, vibration, or age, causing a permanent RAM error. This is a diagnosis of exclusion.
   How to confirm: This is a diagnosis of exclusion. If software is up-to-date, and power/ground circuits are verified to be good (stable voltage, low resistance on grounds), the PCM itself is the likely culprit. The code will typically return immediately after being cleared.
   Typical fix: Replace the PCM and program it to the vehicle's VIN. This can be done by the dealer or by a third-party service that provides pre-programmed modules.
   Est. part cost: $800-$1500

Rare But Worth Checking

• Poor PCM Power or Ground Connections: Corrosion or loose connections at the PCM connector, chassis grounds, or battery terminals can cause intermittent voltage supply, mimicking an internal module fault. A visual inspection and voltage drop test are worthwhile before condemning the module.
• Aftermarket Tuner or Programmer: An improperly installed or poorly designed aftermarket performance tuner can corrupt the PCM's software, leading to P0604 and other errors. Returning the vehicle to the stock tune is a critical diagnostic step if a tuner is present.
• Failing Alternator: → Shop Alternator An alternator with a faulty voltage regulator can produce voltage spikes or excessive AC ripple voltage, which can damage or disrupt sensitive control modules like the PCM, triggering memory errors.

Diagnosis Steps

1. Scan for All Codes: Use an OBD-II scanner to read all stored codes. Note if P0604 appears with other codes, especially emissions-related ones (P20EE, P2002), as this strongly suggests a software update is the fix.
2. Check for TSBs: Have a dealer or qualified shop check your VIN for any open recalls or Technical Service Bulletins related to the PCM. This is the most common fix and should be the first step.
3. Inspect Battery and Charging System: Visually inspect all battery terminals for corrosion. Test both batteries (if equipped) individually. Voltage should be above 12.4V at rest. During cranking, voltage should not drop below 9.6V. With the engine running, verify the alternator output is stable and between 13.5V and 14.8V.
4. Inspect PCM Wiring and Grounds: Check the main PCM connectors for any signs of damage, corrosion, or moisture. Inspect the main engine and chassis ground straps to ensure they are clean, tight, and have less than 0.1 Ω of resistance.
5. Perform PCM Software Update: If an update is available, have it performed by a dealer or qualified shop. After the flash, the codes must be cleared and the vehicle test-driven. The key may need to be left off for over a minute after the flash to ensure the module powers down correctly.
6. Suspect the PCM: If the code returns immediately after a software update and all power/ground checks pass, the PCM itself has likely failed and requires replacement.

Parts You'll Likely Need

• Powertrain Control Module (PCM) Software Update — This is the most common fix for P0604 on this platform, as mandated by multiple manufacturer TSBs to correct software glitches.
  Trusted brands: Mopar (Dealer Service)
  OEM price range: $150-$275
  Aftermarket price range: N/A
• Battery (OEM #BBAH7L48 (Example, verify fitment)) — A weak battery (or pair of batteries on diesel models) is a frequent cause of module memory errors during startup. They must be replaced in pairs on Cummins models.
  Trusted brands: Interstate, Duralast, ACDelco
  OEM price range: $200-$250
  Aftermarket price range: $150-$220
• Powertrain Control Module (PCM) (OEM #68331214AB (6.4L Hemi example), 68449495AE (6.7L Cummins example) - Varies by VIN, must be verified.) — This is only needed if the module has a confirmed internal hardware failure after software updates and power/ground checks have been performed.
  Trusted brands: Mopar, Flagship One, Auto Computer Exchange
  OEM price range: $1000-$1500
  Aftermarket price range: $600-$900

Related Codes That Often Appear With This One

• P0607 — This code for 'ECU Internal Performance' is another generic internal module fault code often set alongside P0604, frequently pointing to the same software or voltage-related root causes. [Bulletin #1806623]
• P20EE — This code for 'SCR NOx Catalyst Efficiency' is often addressed by the same PCM software updates that fix P0604, especially on Cummins models. Seeing them together is a strong indicator that a PCM reflash is needed.
• P2002 — This code for 'Diesel Particulate Filter Efficiency' is also frequently bundled into the same software updates as P0604, further strengthening the case for a software-based repair.
• P060C — This code for 'Internal Control Module Main Processor Performance' is another internal self-check failure that can be triggered by the same software or voltage issues. [Bulletin #18-044-26]

Technical Service Bulletins (TSBs) & Recalls

• 18-044-26: Mentions P0604-00 as an Internal Control Module RAM Error. [Bulletin #18-044-26]
• 1806623: Lists P0604-00 - Internal Control Module Ram. [Bulletin #1806623]
• 1810122REVA: Lists P0604-00 - Internal Control Module Ram. [Bulletin #1810122REVA]
• 18-052-19 REV. A: Lists P0604-00 - Internal Control Module Ram. [Bulletin #18-052-19 REV. A]
• 18-002-14 REV. B: Notes P0604 can be caused by enabling the remote throttle feature and is fixed by a software update.

Platform-Specific Known Issues

• Multiple TSBs (e.g., 18-044-26, 1806623, 1810122REVA, 18-052-19 REV. A) list P0604 as a known issue, often addressed with a PCM software update. [Bulletin #18-044-26, Bulletin #1806623, Bulletin #1810122REVA, Bulletin #18-052-19 REV. A]
• TSB 18-002-14 REV. B specifically states that P0604 can be set by enabling the remote throttle feature and is corrected by a PCM reflash.

Mechanic-Grade Diagnostic Values

• PCM Ground Circuit Resistance to Chassis Ground — expected: Below 0.1 Ω. Failure: Resistance above 0.1 Ω indicates a poor ground connection that can cause voltage anomalies.
• PCM Power/Ground Circuit Voltage Drop — expected: Should not exceed 0.05 volts (50 millivolts). Failure: A voltage drop higher than 50mV points to excessive resistance from corrosion or a loose connection.
• Cranking Voltage at Battery — expected: Should stay above 9.5V - 9.6V. Failure: Dropping below 9.5V indicates a weak battery unable to supply sufficient power for all modules during startup.
• Alternator Charging System Voltage (Engine Running) — expected: Stable between 13.5V and 14.8V. Failure: Voltage outside this range indicates a faulty alternator or voltage regulator which can disrupt the PCM.

Scan Tool Commands That Help

• wiTECH (OEM Dealer Tool): PCM Reprogram/Reflash — This is the primary repair procedure when P0604 is caused by outdated software, as documented in multiple TSBs. It overwrites the problematic software with an updated version.
• wiTECH (OEM Dealer Tool): PCM Configuration routine — This routine must be performed after a successful PCM reflash to ensure all vehicle options and parameters (like VIN and immobilizer data) are correctly set in the newly programmed module.
• wiTECH (OEM Dealer Tool): Inducement Timer Reset — Mentioned in TSB 18-002-14 REV. B, this function is used after a software update related to emissions system faults that can accompany P0604.

Wiring & Ground Locations

• Main Engine-to-Chassis Ground — Typically a large braided strap running from the engine block to the vehicle's firewall or frame rail.. A corroded or loose main ground can create system-wide electrical instability, including unstable voltage to the PCM, which can lead to memory errors like P0604.
• Auxiliary Battery Ground Splice (Cummins) — A black/tan wire, often in a 1" conduit passing along the front of the engine, that eventually connects to the passenger side (auxiliary) battery negative terminal.. This wire contains critical ground splices for the PCM. Corrosion or looseness at the battery tray connector or within the harness splices is a known failure point that can cause intermittent PCM issues.
• TIPM Connector C130 (Blue) — Located on the underside of the Totally Integrated Power Module (TIPM), which is the main fuse box in the engine bay.. This connector carries signals between the TIPM and the PCM. Corrosion on its pins, especially the ground control signal from the ECM (Pin 31), can cause power-related DTCs that mimic an internal PCM failure.

Real Owner Repair Stories

• Cumminsforum.com user (2014 Ram 3500 6.7L) — P0604 code appeared. The truck would sometimes start and then die, while other times it would run fine.
  ❌ Tried (didn't work) Dealer performed a PCM reflash (software update)., Replaced both batteries with new ones.
  ✅ What actually fixed it The Totally Integrated Power Module (TIPM), the main fuse box, was faulty and causing voltage issues for the PCM. Replacing the TIPM resolved the P0604 code.

When the Usual Fixes Don't Work

• In one documented case on a 2014 Ram 3500, the common fixes of a PCM software update and replacing both batteries did not resolve the P0604 code. The actual root cause was a faulty Totally Integrated Power Module (TIPM/fuse box) that was providing unstable voltage to the PCM. Replacing the TIPM ultimately fixed the problem, highlighting an important diagnostic path when the most common solutions fail.

OEM Part Supersession History

• 68265558AA, 68293842AA → 68293842AB — Standard revision incorporating software and potential hardware updates for improved reliability, likely for 2016-2017 models.
  Heads up: Using a PCM from a different model year, engine, or transmission type (e.g., Aisin vs. 68RFE) will not work even if it physically connects. The module must be correct for the specific vehicle configuration and programmed with the correct VIN.

Model Year Variations Within This Range

• 2019-2020 (5th Gen): The 5th generation Ram 2500 uses different PCM hardware (e.g., part number family 68363277AA) compared to the 4th generation (e.g., 68293842AB for 2016-17). While the P0604 code's meaning is the same, the specific software updates and part numbers are not interchangeable.