P2100 on 2019 Ram 2500: Electronic Throttle Control Motor Circuit Causes and Fixes

What's Unique About the 2019-2019 Ram 2500

For the 2019 Ram Heavy Duty trucks (2500/3500), this code is specifically addressed by a manufacturer's Technical Service Bulletin (TSB #09-003-20 REV. C). This TSB acknowledges the P2100 code and limp mode symptom, pointing towards a known issue with a specific batch of throttle bodies used during production. The TSB provides a detailed inspection procedure, instructing technicians to check for an 'S1' marking and a Julian date stamp between '2419' and '2549' on the throttle body to identify the faulty parts. This makes the throttle body itself a higher-probability failure point on these trucks compared to generic wiring or sensor issues.

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
• Red 'lightning bolt' Electronic Throttle Control (ETC) warning light is flashing
• Vehicle enters 'limp home mode' with drastically reduced engine power and acceleration
• No throttle response or delayed throttle response
• Unresponsive accelerator pedal, engine will only idle
• Rough or unstable idle
• Engine may stall
🎬 Watch: Understanding the Service Electronic Throttle Control warning and its causes.

Most Likely Causes

1. Faulty Electronic Throttle Body Assembly 🔴 High Probability → Shop Fuel Injection Throttle Body A specific batch of throttle bodies installed on 2019-2020 models are known to be problematic, as identified in TSB 09-003-20 REV. C. The internal motor circuit fails, creating the 'open circuit' condition. This issue is common enough that the TSB provides specific manufacturing date codes to identify the faulty parts.
   How to confirm: Follow the inspection procedure in TSB 09-003-20 REV. C. Inspect the throttle body for an 'S1' marking. If 'S1' is present, check the four-digit stamped Julian date. If the date is on or between 2419-2549 and there is no green dot near the barcode, the throttle body is faulty and requires replacement. If the TSB doesn't apply, testing the motor's resistance with a multimeter can confirm an internal open circuit. The resistance between the ETC Positive and ETC Negative circuits should be between 2.5 and 25 Ohms.
   Typical fix: Replace the entire throttle body assembly and the corresponding seal. 🎬 See this step-by-step 6.7L Cummins throttle body replacement walkthrough. The OEM part number depends on the engine. After replacement, an 'ETC Relearn' procedure must be performed using a scan tool or by a manual key-on/pedal-press sequence.
   Est. part cost: $200-$800
2. Damaged Wiring or Connector 🟡 Medium Probability The wiring harness to the throttle body can be susceptible to damage from heat, vibration, or being pinched during other engine service. One owner on a forum noted that their P2100 code was caused by the oil filter crushing the wire harness during a change.
   How to confirm: Visually inspect the wiring harness leading to the throttle body for any signs of chafing, pinching, melting, or corrosion. Pay close attention to areas where the harness is near hot components or was disturbed during recent repairs. Disconnect the connector and check for bent, pushed-out, or corroded pins. Use a multimeter to check for continuity on the two motor control wires between the PCM and the throttle body connector; resistance should be below 5.0 Ohms.
   Typical fix: Repair the damaged section of the wire or replace the connector pigtail. Ensure the harness is properly secured away from heat sources or sharp edges.
   Est. part cost: $10-$50
3. Software Glitch ⚪ Low Probability
   How to confirm: This is difficult to confirm without a trip to the dealer. If the throttle body and wiring are confirmed to be good, but the code persists or returns intermittently, a software issue may be the cause. This should be considered before replacing an expensive PCM.
   Typical fix: A dealer may need to reprogram the Powertrain Control Module (PCM) with the latest available software. One owner on Reddit reported that their intermittent limp mode issue was resolved with a software update from the dealer.
   Est. part cost: $0-$200 (for dealer diagnosis/reflash)
4. Low Battery Voltage ⚪ Low Probability Modern trucks are highly sensitive to voltage. A weak or failing battery (dropping below 11 volts) can cause a variety of electronic glitches, including false ETC warnings, as the modules do not receive stable power.
   How to confirm: Test the battery with a multimeter or a load tester. A healthy battery should read approximately 12.6 volts with the engine off and above 13.7 volts with the engine running.
   Typical fix: Recharge or replace the vehicle's battery. Clean any corrosion from the battery terminals.
   Est. part cost: $150-$300

Rare But Worth Checking

• Powertrain Control Module (PCM) Failure: → Shop Engine Control Module (ECM) This is very rare. Before condemning the PCM, all other possibilities, especially the throttle body, its wiring, and potential software updates, must be exhaustively ruled out. A PCM failure will often be accompanied by other unrelated trouble codes.

Diagnosis Steps

1. Scan for Codes: Read all stored Diagnostic Trouble Codes (DTCs). Confirm that P2100 is the primary code.
2. Check for TSBs: Specifically check for TSB #09-003-20 REV. C. Follow its instructions to inspect the throttle body. Look for an 'S1' or 'S2' marking. If 'S2' is present, the bulletin does not apply. If 'S1' is present, check the four-digit Julian date. If the date is between 2419 and 2549 and there is no green dot, the throttle body is the likely cause and should be replaced.
3. Inspect Wiring: Perform a thorough visual inspection of the wiring harness and connector at the throttle body. Look for any damage, corrosion, or loose connections, especially if recent work has been performed on the engine.
4. Check Battery Health: Test the battery voltage with the engine off and running to rule out low voltage as a cause for electronic faults.
5. Test the Circuit: Using a multimeter and wiring diagram, check for proper voltage and ground at the throttle body connector. Check for continuity on the two motor control wires (ETC Positive and ETC Negative) between the throttle body and the PCM; resistance should be less than 5.0 ohms.
6. Test the Throttle Body Motor: If wiring is confirmed to be good, measure the resistance across the two motor pins on the throttle body itself. An out-of-spec reading (requires 2.5-25 ohms) or an infinite reading (OL) indicates an open circuit inside the motor, confirming a bad throttle body.
7. Replace Component: If the TSB applies or the throttle body fails the resistance test, replace the throttle body assembly with the correct part for your engine (6.7L Cummins or 6.4L HEMI).
8. Perform Relearn Procedure: After replacement, perform the Electronic Throttle Control relearn procedure to synchronize the new part with the PCM. This is a critical step.
🎬 Watch: How to perform a throttle body relearn using a scan tool.

Parts You'll Likely Need

• Electronic Throttle Body Assembly (6.7L Cummins) (OEM #68253198AA) — This is the most common failure for P2100 on the Cummins engine, due to internal motor circuit failure. A TSB specifically identifies a faulty batch of these parts on 2019-2020 models. This part number supersedes previous versions.
  Trusted brands: Mopar, Cummins
  OEM price range: $750-$900
  Aftermarket price range: $300-$500
• Electronic Throttle Body Assembly (6.4L HEMI V8) (OEM #53034251AD) — If the vehicle is equipped with the 6.4L HEMI, this is the corresponding throttle body that can fail and cause a P2100 code. The TSB also applies to some gas engine models.
  Trusted brands: Mopar, Bosch
  OEM price range: $250-$350
  Aftermarket price range: $150-$250

Technical Service Bulletins (TSBs) & Recalls

• 09-003-20 REV. C: Addresses MIL illumination with DTC P2100 and limp mode, instructing technicians to inspect the throttle body's Julian date (2419-2549) and markings ('S1' without a green dot) to determine if replacement is necessary.

Platform-Specific Known Issues

• TSB 09-003-20 REV. C was issued for 2019-2020 Ram HD trucks for the P2100 code. It requires an inspection of the throttle body's Julian date (production date between 2419-2549) and markings ('S1') to identify a potentially faulty batch of parts that need replacement.

Mechanic-Grade Diagnostic Values

• Throttle Body Motor Resistance — expected: 2.5 to 25 Ohms. Failure: An infinite (OL) reading indicates an open circuit. A reading outside the specified range indicates a faulty motor.
• ETC Motor Circuit Continuity — expected: Below 5.0 Ohms. Failure: A reading above 5.0 Ohms indicates excessive resistance or an open in the wiring between the PCM and the throttle body connector.
• Battery Voltage (Engine Off) — expected: ~12.6 Volts. Failure: A reading below 12.4V suggests a discharged battery. A reading below 11V can cause various electronic module glitches, including false ETC faults.
• Charging System Voltage (Engine Running) — expected: 13.7 to 14.7 Volts. Failure: A reading below 13.7V may indicate a problem with the alternator, which can lead to an undercharged battery and electronic issues.

Scan Tool Commands That Help

• wiTECH (or equivalent professional scan tool): ETC Relearn / Throttle Follower Test — This function is mandatory after replacing the throttle body to teach the PCM the new component's idle and full-range positions. It can also be used to command the throttle plate to move, verifying the motor and wiring are functional.
• wiTECH (or equivalent professional scan tool): View Live Data - ETC Motor — To monitor the commanded versus actual throttle position. If the PCM commands a change but the actual position doesn't respond, it points to a failure in the throttle body motor or its circuit.

Wiring & Ground Locations

• Throttle Body Connector (6.7L Diesel) — On the electronic throttle body, located on the driver's side of the engine, part of the intake system.. This is the primary connection point for the throttle motor. The P2100 code is for an open circuit, so checking for pushed-out pins, corrosion, or damage at this connector is a critical first step. The circuit wires are often designated K447 (ETC Positive) and K448 (ETC Negative) in service literature.
• Engine/Chassis Grounds — Multiple locations. On 5th Gen Rams, there are numerous ground points on the frame, firewall, and near the battery. A user on the Turbo Diesel Register forum was searching for a full list to solve a 'service throttle control' message.. While P2100 is a specific circuit code, a poor engine or PCM ground can cause erratic behavior in electronic components. Some owners on forums have reported improved throttle response and idle stability on Hemi engines by adding a supplemental ground wire from a throttle body mounting bolt directly to the chassis or battery negative post, suggesting the factory grounding can sometimes be insufficient.

Real Owner Repair Stories

• DodgeForum.com user (2005 Ram 1500 5.7L) — P2100 code, engine would only idle, no throttle response. The throttle body did not make its usual 'click' sound on key-on.
  ❌ Tried (didn't work) Disconnecting and reconnecting the throttle body plug multiple times.
  ✅ What actually fixed it The issue occurred immediately after installing new heads. Another user suggested the cause was likely a pinched wire in the throttle body harness that was damaged during the head installation.

OEM Part Supersession History

• 68205987AA, 68210508AA, 68253197AA → 68253198AA — Revisions by the manufacturer to improve reliability and address failures leading to codes like P2100, as noted in TSB 09-003-20 REV. C.