P1477 on 2014-2015 Ram 2500 6.7L Cummins: Intake Air Diverter Valve Circuit Short Fixes

What's Unique About the 2014-2015 Ram 2500

What's unique to this Ram platform is that code P1477 is very frequently a 'phantom' code caused by overly sensitive software in the Powertrain Control Module (PCM). Multiple Technical Service Bulletins (TSBs) have been issued by Ram instructing dealers to resolve this and a cluster of other codes by simply reprogramming the PCM with updated software. These TSBs confirm the issue affects both the Ram 2500 and 3500 models with the 6.7L engine. Before suspecting a hardware failure, the first step should always be to check if the vehicle's software is up to date, as this is the most common and least expensive fix.

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 (Malfunction Indicator Lamp) is on.
• A 'Service Air Filter' message may appear on the Electronic Vehicle Information Center (EVIC), though this is more commonly associated with related codes like P227F.
🎬 See how to diagnose the 'Service Air Filter' message

Most Likely Causes

1. Outdated Powertrain Control Module (PCM) Software 🔴 High Probability Ram has released multiple TSBs (e.g., 18-045-15, 18-054-16, 18-037-16 REV. A) advising that a PCM reflash can correct this and other erroneously set codes. These updates were specifically created to resolve these phantom codes.
   How to confirm: A Ram dealer or a properly equipped independent shop can check the current software version against the latest available version using a wiTECH scan tool. This is the only definitive way to know if an update is available.
   Typical fix: Reprogramming the PCM with the latest software version. This is a dealer-only or specialized shop procedure.
   Est. part cost: $0
2. Damaged Wiring, Connector, or Blown Fuse 🟡 Medium Probability The wiring harness to the airbox is exposed to engine heat and vibration, potentially leading to chafing, broken wires, or corrosion in the connector, causing a short to ground. The circuit is protected by a fuse that can blow.
   How to confirm: First, check fuse F78 (10A) in the main 🎬 Watch: How to find the air diverter valve fuse location under-hood fuse box. If the fuse is good, visually inspect the wiring harness and connector going to the Intake Air Diverter Valve on the airbox. Use a multimeter to test the sensor's signal wire for continuity to ground.
   Typical fix: Replace the blown fuse. Repair the damaged section of the wire or replace the connector pigtail.
   Est. part cost: $1-$40
3. Failed Intake Air Diverter Valve Assembly ⚪ Low Probability The position sensor is integrated into the diverter valve actuator motor. The motor's internal circuit board can corrode or fail, creating a permanent short circuit. The actuator is not sold separately by Mopar, so the entire air filter housing must be replaced.
   How to confirm: If the PCM software is up-to-date, the fuse is good, and the wiring tests good, the valve/sensor assembly is the likely point of failure. A capable scan tool can command the valve's movement and read the position data to confirm it is unresponsive.
   Typical fix: Replace the entire air filter housing assembly which contains the diverter valve and actuator.
   Est. part cost: $200-$400

Diagnosis Steps

1. Check for Technical Service Bulletins (TSBs) related to your vehicle's VIN. Many TSBs for this code point to a software update as the primary fix.
2. Using a scan tool, check if other common phantom codes (like P2281, U110E, P20E8) are present. If so, a software issue is highly probable.
3. Check fuse F78 (a 10A fuse) in the main engine fuse box located under the hood.
4. If the fuse is good, perform a thorough visual inspection of the wiring harness and connector for the Intake Air Diverter Valve, located on the side of the air filter housing. Look for chafing, melting, or corrosion.
5. Using a multimeter, disconnect the valve connector and test the position sensor signal wire in the harness for a short to ground.
6. If the wiring and software are confirmed to be good, the Intake Air Diverter Valve/Sensor assembly is the most likely cause of the fault. Replacement of the entire air filter housing is required.

Parts You'll Likely Need

• Intake Air Cleaner Assembly (OEM #68321026AC (example, confirm with dealer by VIN)) — If the cause is not software or wiring, the internal position sensor/actuator has likely failed. The actuator is integrated into the air filter housing and is not sold separately by Mopar, requiring replacement of the entire assembly.
  Trusted brands: Mopar
  OEM price range: $250-$400
  Aftermarket price range: $200-$350
• Intake Air Diverter Valve Connector Pigtail — The connector itself can become brittle or corroded from heat and vibration, causing a short. Replacing the pigtail is a common wiring repair if the connector is the point of failure.
  Trusted brands: Dorman, Mopar
  OEM price range: $30-$50
  Aftermarket price range: $15-$40

Related Codes That Often Appear With This One

• P2281 — Air Leak Between MAF And Throttle Body. This code is frequently listed alongside P1477 in TSBs that are resolved with a PCM software update.
• U110E — Lost Ambient Temperature Message. Also commonly grouped with P1477 in software-related TSBs.
• P20E8 — (Diesel Exhaust Fluid) Reductant Pressure Too Low. The presence of this diesel-specific code with P1477 confirms the issue is on a Cummins engine and is often part of the same software glitch.
• U1421 — Implausible Ignition Key Off Time Received. Another code often resolved by the same PCM reflash.
• U3017 — Control Module Timer/Clock Performance. This code is mentioned in TSB 18-045-15 for 2014 models as being resolved by the same software update.

Technical Service Bulletins (TSBs) & Recalls

• 18-076-22: Groups P1477 with numerous other codes fixed by a PCM software update for 2015 models.
• 18-054-16: Supersedes a previous TSB for 2014 models, listing P1477 as a code that can be fixed by a PCM reflash.
• 18-037-16 REV. A: Lists P1477 for 2015 models as part of a group of DTCs addressed by a PCM software update.
• 18-045-15: Notes that for 2014 models, P1477 may be set and can be cleared by reprogramming the PCM.

Platform-Specific Known Issues

• A high number of TSBs (e.g., 18-045-15, 18-037-16 REV. A, 18-054-16, 18-076-22) indicate that P1477, often with a cluster of other codes, can be triggered by software anomalies in the PCM, making a dealer reflash the primary recommended fix.
• The software updates often include other powertrain enhancements, such as improved EGR valve response, A/C pressure sensor updates, and cold idle stability improvements, making the reflash beneficial even if P1477 is the only code present.

Mechanic-Grade Diagnostic Values

• Sensor Ground Wire Voltage (backprobed at connector, connected) — expected: Less than 50 mV. Failure: Voltage significantly higher than 50 mV indicates a poor ground connection.
• Reference Voltages (based on similar 5-pin 6.7L Cummins actuator) — expected: Pin 1: 12V+ (Battery Voltage), Pin 2: 5V (Signal), Pin 3: Sensor Ground, Pin 4: 5V (Reference), Pin 5: Motor Ground. NOTE: This pinout is for the throttle valve, not the diverter valve, but illustrates the expected types of signals in the circuit.. Failure: Absence of 12V power, 5V reference, or a good ground points to a wiring or PCM issue, not a failed component.

Scan Tool Commands That Help

• wiTECH: Active Airbox Actuator Test / Bidirectional Control — After confirming software is up-to-date and wiring/fuse are good. This command allows the technician to manually open and close the diverter valve while monitoring the 'desired' vs 'actual' position sensor data. If the valve doesn't move when commanded, or the position data doesn't change, it confirms a failure in the actuator motor or sensor assembly.

Wiring & Ground Locations

• Intake Air Diverter Valve Actuator Connector — On the side of the main air filter housing, near the bottom. To access it, the air housing must be unbolted and lifted partially out of the engine compartment.. This is the primary connector to inspect for corrosion, damage, or to perform voltage and continuity tests for the diverter valve motor and position sensor circuit.

OEM Part Supersession History

• 68321026AB, 68321026AC, 68321026AD → 68321026AE — Standard part revision and improvement by the manufacturer.
  Heads up: The newest part number (68321026AE) is the correct service replacement for all previous versions on this platform.

Model Year Variations Within This Range

• 2014-2015: For the Ram 2500 and the Active Air system related to code P1477, there are no significant mechanical or electrical differences between the 2014 and 2015 model years. TSBs for the software fix apply to both years.