P0204 on 2014-2020 Ram 2500: Injector Circuit/Open - Cylinder 4 Causes and Fixes

What's Unique About the 2014-2020 Ram 2500

On Ram trucks, the cause of P0204 often depends on the engine. For the 6.7L Cummins diesel, the injector wiring harness, which is located under the valve cover and often integrated with the valve cover gasket, is a well-documented failure point due to constant heat and vibration. Forum users on CumminsForum frequently cite this as the first place to look. For the gasoline Hemi engines (6.4L or 5.7L), the issue can be either the injector itself or the external wiring harness becoming brittle and cracking from engine heat. The provided Technical Service Bulletin #18-099-22 REV. A, which lists P0204 for 2019-2020 gasoline and diesel models, points towards a failing CP4 high-pressure fuel pump on diesels, which can send debris through the system causing injector codes. This TSB was later replaced by recall Y78.

Diagnostic Flowchart

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

Generation note: This range covers two generations of the Ram 2500: the end of the fourth generation (2014-2018) and the start of the fifth generation (2019-2020). For 2019, the 5.7L V8 was discontinued, and the 6.4L Hemi V8 became the standard gas engine, paired with a new 8-speed transmission. The 6.7L Cummins diesel also saw updates, including a controversial switch to the Bosch CP4 injection pump for 2019-2020 models, which is subject to recall Y78 for high-pressure failure that can trigger injector codes like P0204. While the core causes of P0204 remain similar, part numbers and harness routing may differ between these generations.

Symptoms You May Notice

• Check Engine Light is on
• Engine misfire, which feels like a shake or shudder, especially at idle
• Rough running or engine shuttering
• Reduced engine power and slow acceleration
• Poor fuel economy
• Excessive white or black smoke from exhaust (more common on diesel models)
• Engine may enter a 'limp-in mode' with restricted speed

Most Likely Causes

1. Faulty Fuel Injector #4 🔴 High Probability → Shop Fuel Injector The internal electronic coil of the injector can fail from heat cycles and age, creating an open circuit. This is a common failure for both gasoline and diesel models, though wiring should be checked first on Cummins engines.
   How to confirm: Measure the resistance of the injector with a multimeter. For a Cummins, the reading should be very low, between 0 and 1.0 ohms. For a Hemi, it is typically 11-14 ohms. An 'OL' (Open Line) or out-of-spec reading indicates a bad injector. A definitive test is to swap the #4 injector with an adjacent one (like #2 or #6). Clear the codes and run the engine. If the code changes to P0202 or P0206, the injector is faulty.
   Typical fix: Replace the failed fuel injector. 🎬 See this walkthrough for replacing Hemi fuel injectors On Cummins engines, it is critical to also replace the high-pressure fuel connector tube to prevent leaks.
   Est. part cost: $50-$150 (Hemi), $300-$600 (Cummins)
2. Damaged Fuel Injector Wiring or Connector 🔴 High Probability → Shop Fuel Injector On 6.7L Cummins engines, the harness under the valve cover is exposed to intense heat and vibration, causing wires to become brittle and crack. The rear connector serves cylinders 4, 5, and 6. On Hemi engines, the external harness can suffer from heat damage, and the plastic connector at the injector can become brittle and fail. Rodent damage is also a possibility.
   How to confirm: Visually inspect the wiring harness leading to injector #4 for any signs of cracking, chafing, or melting. On Cummins engines, perform a 'wiggle test' on the main harness connector on the valve cover while the engine is idling to see if the misfire changes. Use a 'noid light' to test for a pulse signal at the injector connector. If the light doesn't flash while cranking the engine, the problem is in the wiring or the PCM.
   Typical fix: Repair the damaged section of wire or replace the injector connector pigtail. For Cummins engines, this often requires replacing the entire injector harness assembly (which may be integrated with the valve cover gasket). The terminal nuts connecting the harness to the injectors must be torqued to a very low spec, typically around 8.8 in-lbs.
   Est. part cost: $15-$50 (pigtail), $100-$250 (Cummins harness)
3. Faulty Powertrain Control Module (PCM) ⚪ Low Probability → Shop Engine Control Module (ECM) While rare, the internal injector driver circuit within the PCM can fail due to heat stress or solder joint fatigue.
   How to confirm: This should only be considered after the injector and wiring have been definitively ruled out with resistance and continuity tests. A professional shop can perform advanced diagnostics, such as using an oscilloscope to check the driver signal at the PCM pin, to confirm the failure. A user on DodgeForum.com confirmed a PCM replacement fixed their P0204 issue after other diagnostics failed.
   Typical fix: Replace and reprogram the Powertrain Control Module. Some specialized shops may be able to repair the driver on the circuit board.
   Est. part cost: $600-$1200

Rare But Worth Checking

• Bent or Corroded Pins:

Diagnosis Steps

1. Read the code from the PCM using an OBD-II scanner and note any other codes present, especially P0304 or P2149.
2. Visually inspect the wiring and connector for cylinder #4. For Hemi, check for melted plastic near the manifold. For Cummins, inspect the large pass-through connector at the rear of the valve cover.
🎬 Watch: Troubleshooting the Cummins injector circuit and harness
3. Perform a 'noid light' test. Disconnect the harness from injector #4, plug in the noid light, and crank the engine. A flashing light indicates the PCM and wiring are sending a signal. No light points to a wiring or PCM issue.
4. If the noid light flashes, test the injector. Turn the engine off, disconnect the injector, and measure its internal resistance with a multimeter. Compare the reading to the manufacturer's specification (less than 1.0 ohm for Cummins, ~11-14 ohms for Hemi).
5. If the injector resistance is out of spec (e.g., open circuit), it is faulty and needs replacement.
6. If the injector resistance is good, perform an injector swap. Move the #4 injector to another cylinder (e.g., cylinder #6). Clear the codes and run the engine. If the code moves to P0206, the injector is the problem. If P0204 returns, the issue is confirmed to be in the wiring or PCM.
7. If the noid light does not flash, check the wiring harness. For Cummins, this means testing continuity of the under-valve-cover harness from the pass-through connector to the injector terminals. For all engines, check continuity from the PCM connector to the injector connector. Resistance should be less than 5 ohms.
8. If all wiring and the injector test good, the final possibility is a failed injector driver in the PCM, which typically requires professional diagnosis to confirm.

Parts You'll Likely Need

• Fuel Injector (OEM #53032712AB (5.7L Hemi), 05037479AC (6.4L Hemi), 68439214AA (6.7L Cummins 2019-2020)) — The injector's internal coil is a primary failure point, causing an open circuit.
  Trusted brands: Mopar, Bosch, Standard Motor Products
  OEM price range: $100-$180 (Hemi), $450-$600 (Cummins)
  Aftermarket price range: $40-$90 (Hemi), $2

Related Codes That Often Appear With This One

• P0304 — This code means 'Cylinder 4 Misfire Detected.' Since P0204 indicates a fuel delivery circuit problem for that cylinder, a misfire is the direct and expected result.
• P0201, P0202, P0203, P0205, P0206 — Seeing multiple injector circuit codes together strongly suggests a problem with a shared power or ground wire in the harness, or a failure of the injector driver bank in the PCM. TSB #18-099-22 REV. A also notes that multiple injector codes can appear on 2019-2020 Cummins models due to a failing CP4 fuel pump.
• P2149 — On Cummins engines, this code means 'Fuel Injector Group B Supply Voltage Circuit/Open,' which corresponds to cylinders 4, 5, and 6. Seeing this with P0204 is a very strong indicator of a problem with the rear injector wiring harness or its pass-through connector on the valve cover.

Technical Service Bulletins (TSBs) & Recalls

• 18-099-22 REV. A: For 2019-2020 models, this TSB lists P0204 and other injector codes as potential results of a failing high-pressure fuel pump (CP4). It advises checking for metal contamination in the fuel system. This TSB was ultimately superseded by safety recall Y78 for the CP4 pump.
• 9002688: An older but still relevant TSB for Cummins engines that explicitly warns technicians to check the wiring loom/connector in the valve cover gasket before replacing injectors for P020x codes.

Platform-Specific Known Issues

• Cummins Under-Valve-Cover Harness Failure: → Shop Engine Valve Cover For the 6.7L Cummins, the most probable cause of a P0204 is the wiring harness located beneath the valve cover. The harness for the rear three cylinders (4, 5, 6) is particularly susceptible to failure from constant heat and vibration. The wires can become brittle and break, or the connector pins can lose tension. Often, this fault appears with P2149. TSB 9002688 specifically advises checking this harness before replacing an injector. The fix is to replace the harness section (Part # 5149207AA for 2013-2018 models).
• Hemi Injector Connector Heat Damage: On 5.7L and 6.4L Hemi engines, the wiring harness is routed over the top of the hot intake manifold. The plastic connector for cylinder #4 (typically on the passenger side) can become brittle and crack, or the wires leading to it can be damaged by heat, leading to an open circuit. A visual inspection and a 'wiggle test' of the connector and nearby wiring can often pinpoint the issue. Replacing the connector with a pigtail is a common and inexpensive repair.
• 2019-2020 Cummins CP4 Fuel Pump Failure: For 2019-2020 models with the 6.7L Cummins, the introduction of the Bosch CP4 high-pressure fuel pump brought a new potential cause. These pumps can fail internally, sending metallic debris throughout the entire fuel system. This debris can damage the injectors, causing electrical faults like P0204. TSB 18-099-22 REV. A and recall Y78 address this issue. If P0204 is accompanied by P0087 (Fuel Rail Pressure Too Low), a CP4 failure should be suspected.

Mechanic-Grade Diagnostic Values

• 6.7L Cummins Fuel Injector Solenoid Resistance — expected: Less than 1.0 Ohm, and greater than 0 Ohms.. Failure: An infinite resistance (Open Line) reading indicates a failed open solenoid. A reading of exactly 0 may indicate a short.
• 5.7L/6.4L Hemi Fuel Injector Resistance — expected: Approximately 11 to 16 Ohms.. Failure: A reading significantly outside this range, or showing an open circuit, indicates a faulty injector.
• 6.7L Cummins Injector Terminal Nut Torque — expected: 8.8 in-lbs (approximately 1 Nm).. Failure: Over-tightening can damage the injector solenoid posts, causing an open circuit. Under-tightening can cause a poor connection and high resistance.
• Injector Circuit Continuity (PCM to Injector) — expected: Less than 5.0 Ohms.. Failure: Resistance higher than 5.0 Ohms indicates excessive resistance in the wiring harness, which can trigger an open circuit code.

Scan Tool Commands That Help

• wiTECH or AlfaOBD: Injector Kill Test / Cylinder Cutout Test — This bidirectional command allows the technician to electronically disable cylinder #4's injector while the engine is running. If there is no change in engine idle when the injector is killed, it confirms that cylinder was not contributing, verifying the fault. This is a definitive way to confirm the misfire without disassembly.
• wiTECH or AlfaOBD: Cylinder Performance Test — This is a more comprehensive automated test that measures the contribution of each cylinder to engine speed. It can quickly identify which cylinder(s) are underperforming, confirming the location of the misfire associated with P0204.
• wiTECH: View Network Topology — On newer models, the wiTECH tool displays a color-coded topology map of all vehicle modules. This can help quickly identify communication issues or DTCs in related modules (like the FCM) that could be influencing the PCM's operation.

Wiring & Ground Locations

• PCM C1 Connector (6.7L Cummins) — On the Powertrain Control Module (PCM), located on the driver's side of the engine block.. This connector contains the specific driver circuits for the injectors. For P0204, the key pins are (K614) for the High Side Driver and (K14) for the Low Side Driver. Testing for continuity and shorts between these pins and the valve cover pass-through connector is a critical diagnostic step.
• Valve Cover Pass-Through Connector (6.7L Cummins) — The large electrical connector(s) mounted on the valve cover, connecting the main engine harness to the under-cover injector harness.. This is a major weak point. The rear connector serves cylinders 4, 5, and 6. Corrosion or damage to the pins in this connector can cause P0204, often along with P2149. Wiggling this connector while the engine runs can often reveal an intermittent fault.
• Engine Ground Points — Multiple locations, including near the battery negative terminal, on the firewall near the wiper motor, and on the engine block itself.. While not a direct cause of a single injector code, a poor main engine or PCM ground can cause a host of erratic electrical issues, including faulty sensor readings and incorrect driver operation. Verifying clean, tight grounds is a foundational step in any electrical diagnosis.

Real Owner Repair Stories

• Mechanic Lifestyle YouTube Channel (Land Rover Discovery (demonstrating a universal P0204 fix)) — Check engine light on, engine misfiring.
  ❌ Tried (didn't work) Initial assumption was a bad fuel injector.
  ✅ What actually fixed it The electrical connector for the #4 fuel injector was not pushed in all the way and had come loose. The retaining clip was also missing/broken. Pushing the connector on securely until it clicked and ensuring the clip was engaged resolved the P0204 code.
• VAG CARS YouTube Channel (Volkswagen Caddy (demonstrating a universal P0204 fix)) — Check engine light on with code P0204.
  ✅ What actually fixed it A resistance check on the #4 injector showed an open circuit (infinite resistance), while other injectors were in spec. Replacing the faulty fuel injector and then coding the new injector to the ECU using a diagnostic tool completely fixed the issue. The fault code was cleared and did not return on a test drive.

OEM Part Supersession History

• Not specified → 68439214AA — The part number 68439214AA is listed as a 'Fan Module' in Mopar parts catalogs, but was also listed as the OEM part number for a 2019-2020 Cummins fuel injector in the Pass 2 data. This appears to be an error in the original data; 68439214AA is a radiator cooling fan module.
  Heads up: This part is not a fuel injector. Using this part number will result in ordering the wrong component.

Model Year Variations Within This Range

• 2019-2020: For the 6.7L Cummins, these model years switched to a Bosch CP4 high-pressure fuel pump. Failures of this pump are known to create metallic debris that can damage injectors, potentially leading to electrical fault codes like P0204 as the injector fails. This issue led to recall Y78.
• 2014-2018: These 6.7L Cummins models used the more reliable CP3 high-pressure fuel pump. While injector failures still occur, they are less likely to be caused by catastrophic fuel pump failure sending debris through the system.