P0606 on 2014 Ram ProMaster: Understanding the Internal Control Processor Fault

What's Unique About the 2014-2014 Ram PROMASTER

For the 2014 Ram ProMaster, the P0606 code is frequently a software issue rather than a hardware failure. Ram released several Technical Service Bulletins (TSBs) indicating that this code, sometimes appearing with others like U0140, can be resolved by updating the PCM's software. This is a crucial distinction, as owners might otherwise assume they need an expensive PCM replacement when a much cheaper software reflash from a dealer is the correct fix. The TSB specifically notes this update can address MIL illumination or less than desired powertrain response.

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
• Vehicle may not start or may be hard to start.
• Engine may stall unexpectedly, especially when coming to a stop.
• Engine surging or bucking when trying to stop.
• Erratic or poor automatic transmission shifting.
• Reduced engine performance and poor fuel economy
• Vehicle enters 'limp mode' with reduced power.
• Other warning lights, like the ABS or traction control light, may illuminate.

Most Likely Causes

1. Outdated PCM Software 🔴 High Probability Ram issued multiple TSBs (#18-088-16, #18-086-15) for the 2014 ProMaster to address this code being set erroneously, often alongside other codes like U0140. This is the most likely cause, intended to fix MIL illumination and powertrain response issues.
   How to confirm: A Ram dealer or a qualified shop with access to OEM service information can check your vehicle's VIN to see if the software updates from the TSBs have been applied. The TSB repair procedure requires a wiTECH scan tool.
   Typical fix: Perform a PCM software update, also known as a 'reflash'. This must be done by a dealer or a shop with the appropriate tools. The TSB specifies maintaining battery voltage between 13.2 and 13.5 volts during the flash process. A dealer reflash may cost between $175 and $300.
   Est. part cost: $0
2. Defective Powertrain Control Module (PCM) 🟡 Medium Probability → Shop Engine Control Module (ECM) If a software update does not resolve the code, the PCM's internal processor may have genuinely failed. This is the default cause when software and external factors are ruled out. In some cases, a failed software update attempt can also damage the ECM/PCM.
   How to confirm: This is diagnosed by exclusion. If a reflash doesn't work and all power/ground circuits are confirmed good, the PCM is the culprit. Sometimes a burnt smell or visible damage can be found on the module itself.
   Typical fix: Replace the PCM and program the new unit to the vehicle's VIN. This can be done with an OEM Mopar part from a dealer or a pre-programmed unit from a third-party rebuilder.
   Est. part cost: $500-$1200
3. Battery or Charging System Malfunction ⚪ Low Probability → Shop Vehicle Battery
   How to confirm: Test the battery and charging system. Check for a stable voltage (approx. 12.6V with engine off, 13.5-14.5V with engine running). Unstable voltage or excessive AC ripple from a failing alternator can confuse the PCM and trigger internal fault codes.
   Typical fix: Replace the battery or repair the charging system (e.g., alternator). In some forum discussions, simply cleaning corroded battery terminals and fully charging the battery has resolved the code.
   Est. part cost: $150-$500
4. Poor PCM Power or Ground Connections ⚪ Low Probability
   How to confirm: Visually inspect the PCM connectors for corrosion, damage, or loose pins. Check the main engine and PCM ground straps for tightness and corrosion. A bad ground can cause a host of strange electrical issues, including a P0606.
   Typical fix: Clean or repair the PCM connectors and ground points. This is a low-cost but essential check before condemning the PCM.
   Est. part cost: $0-$50

Rare But Worth Checking

• Shorted Sensor or Actuator:

Diagnosis Steps

1. Scan the vehicle for all fault codes. Note if P0606 appears with U0140, P0456, P0335, or P2610, as this strongly points to the TSB software issue.
2. Contact a Ram dealer with your VIN to determine if TSBs #18-088-16 or #18-086-15 apply and if the software update has been performed.
3. If the TSB is open, have the PCM reflashed. This is the most probable solution. A dealer will use a wiTECH tool and ensure stable battery voltage during the process.
4. If the code persists after the reflash, perform a full battery and charging system test. Ensure voltage is stable (12.6V off, 13.5-14.5V running) and check for alternator AC ripple.
5. Inspect all power and ground connections to the PCM. Check the main engine-to-chassis ground strap. 🎬 See this guide on ProMaster ground strap locations and symptoms. Clean any corrosion from terminals and connectors.
6. Consider disconnecting the battery for 15-30 minutes to perform a hard reset of the modules. Sometimes this can clear a temporary glitch.
7. If all external factors (software, voltage, connections) are confirmed to be good and the code returns, the PCM is likely faulty and requires replacement.

Parts You'll Likely Need

• Powertrain Control Module (PCM) (OEM #05150794AC, 68190506AD, 5150926) — This is the part that needs to be replaced if a software reflash and circuit checks do not solve the problem. Several part numbers exist and may have been superseded.
  Trusted brands: Mopar (OEM), FS1, Car Computer Exchange (Remanufactured/Rebuilt)
  OEM price range: $800-$1200
  Aftermarket price range: $450-$900

Related Codes That Often Appear With This One

• U0140 — This code, for 'Lost Communication With Body Control Module', is specifically mentioned alongside P0606 in Ram TSBs #18-088-16 and #18-086-15 for the 2014 ProMaster, indicating a strong link to the software glitch.
• P0456 — This code for a small EVAP leak is also mentioned in Ram TSB #18-088-16, suggesting the software glitch could trigger multiple unrelated codes.
• P0335 — Crankshaft Position Sensor Circuit error is another code listed in TSB #18-088-16 REV. A that can be resolved by the PCM software update.
• P2610 — PCM Internal Engine Off Timer Performance is also listed in TSB #18-088-16 REV. A as being related to the software issue.

Technical Service Bulletins (TSBs) & Recalls

• 18-088-16 REV. A: Mentions P0606, U0140, P0456, P0335, and P2610 as codes that can be addressed with a PCM software update for 'less than desired powertrain response'.
• 18-086-15 REV A: Also lists P0606 and U0140 as Diagnostic Trouble Codes that may be resolved with a PCM reflash.

Platform-Specific Known Issues

• TSB Software Update is the Primary Fix: A known software glitch can cause the PCM to incorrectly set code P0606, often along with U0140. Ram addressed this with TSBs #18-088-16 REV. A and #18-086-15 REV A, which involve a PCM software update. This should always be the first step in diagnosis for a 2014 ProMaster.
• Real Owner Experience: Stalling and Surging: On the Turbo Diesel Register forum, a user with a P0606 code described symptoms of the truck surging as if it didn't want to stop. This aligns with the potential for erratic PCM behavior affecting drivability and reinforces why the vehicle should not be driven.
• Real Owner Experience: The Battery Connection: → Shop Vehicle Battery In a thread on RamForum.com, a user with a P0606 code was able to make the Check Engine Light turn off by cleaning the battery posts and leaving the battery disconnected for a couple of hours. This highlights the importance of checking simple electrical connections first.

Mechanic-Grade Diagnostic Values

• PCM Power & Ground Circuit Voltage Drop — expected: No more than 0.05 volts (50 millivolts). Failure: Voltage drop readings higher than 50mV indicate excessive resistance from loose connections or corrosion.
• Battery Voltage (Engine Off) — expected: Approximately 12.6 Volts. Failure: Significantly lower voltage indicates a discharged or failing battery, which can cause spurious PCM codes.
• Charging System Voltage (Engine Running) — expected: 13.5 to 14.5 Volts. Failure: Voltage below 13.5V or above 14.5V suggests a faulty alternator or regulator, which can cause electrical issues that trigger P0606.
• PCM 5-Volt Supply (at PCM Connector) — expected: 5 Volts. Failure: No voltage or incorrect voltage (e.g., 12V) on a 5V reference pin points to an internal PCM fault or a short in a sensor/harness.

Scan Tool Commands That Help

• wiTECH: Reprogram PCM — This is the primary repair procedure specified in TSBs for a P0606 code on this vehicle to install updated software.
• wiTECH: Read DTCs / Clear DTCs — Used to verify the P0606 code and to clear all codes from various modules after a successful PCM reflash.

Wiring & Ground Locations

• Primary Engine/Transmission Ground Strap — A braided strap that connects the transmission case to a bolt on the top of the transmission mount. It is accessible by removing the driver's side headlight.. This is the primary ground for the engine and transmission. A poor connection here can cause inconsistent voltage and corrupted data signals for the PCM, potentially triggering a P0606 code.
• PCM Ground Circuits — Multiple pins on the PCM connectors serve as grounds. For example, on a generic Ram 96-pin connector, pin 42 (BR/WT wire) is a sensor ground. A specific wiring diagram for the ProMaster is required for exact pin locations.. The PCM requires a stable, clean ground reference to operate. A high-resistance or open ground circuit can cause the processor to malfunction and set an internal fault code.
• PCM Power Supply Circuits — Multiple pins on the PCM connectors provide battery power. For example, on a generic Ram 96-pin connector, pin 96 (RD wire) is a Fused B(+) supply. Specific fuse locations can be found in the vehicle's fuse box diagram.. Interrupted or low voltage on the power supply circuits will prevent the PCM from functioning correctly and can lead to a P0606 code.

Real Owner Repair Stories

• YouTube video by 'Mike Salazar Diagnostics' (2014 Ram ProMaster 3.0L Diesel) — Lost communication with ECM after transmission work.
  ❌ Tried (didn't work) Load testing grounds at the ECM.
  ✅ What actually fixed it The original PCM was physically bent and damaged, with a cracked case. The solution was to clone the information from the damaged PCM to a donor PCM, which restored communication and function.
• YouTube video by 'Luis F' (2014 Ram ProMaster 2500) — No start, clicking sound when turning the key.
  ❌ Tried (didn't work) Standard starting procedures.
  ✅ What actually fixed it An additional ground cable was added, running from one of the starter mounting bolts directly to a ground point on the chassis frame near the under-hood fuse box. This provided a better ground path for the starter and engine, resolving the no-start condition.