P0871 on 2019-2020 Ram 2500: Overdrive Pressure Switch Causes and Fixes

What's Unique About the 2019-2020 Ram 2500

The P0871 code is notoriously common and feared by owners of Ram trucks with the 68RFE automatic transmission, which is standard in the 2019-2020 Ram 2500 with the 6.7L Cummins engine. The issue is rarely the sensor itself, but a specific, well-documented mechanical failure: wear inside the transmission valve body's solenoid switch valve (SSV) bore. This wear allows for hydraulic cross-leaks that incorrectly trigger the pressure switch, making this a mechanical problem that presents as an electronic code. While the 68RFE was updated for 2019 models, it is still considered susceptible to this issue.

Diagnostic Flowchart

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

Generation note: The 2019 model year was a transition from the 4th generation (DS) to the 5th generation (DJ) Ram HD trucks. However, this issue is tied to the 68RFE transmission, which was used in both generations with the 6.7L Cummins engine. Therefore, the causes and fixes are consistent across 2019-2020 models regardless of the specific generation.

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on
• Transmission enters 'limp mode', often getting stuck in 4th gear.
• Harsh or erratic shifting, especially hard downshifts when slowing down.
• Delayed gear engagement.
• Inability to use the +/- manual gear selector buttons on the shifter.
• Loss of 5th and 6th gears.
• The 'D' indicator on the dash may disappear.

Most Likely Causes

1. Worn Transmission Valve Body 🔴 High Probability → Shop Transmission Valve Body The solenoid switch valve (SSV) bore within the 68RFE's aluminum valve body is known to wear over time, allowing hydraulic pressure to leak between circuits. This is a well-documented weak point of this transmission design, with some experts estimating it accounts for 90% of P0871 cases. High mileage (over 90k miles) and towing accelerate this wear.
   How to confirm: A transmission specialist will use a scan tool to monitor pressure switch data. The definitive confirmation is observing the overdrive pressure switch as 'Closed' (showing pressure) in gears 1, 2, or 3, which indicates a hydraulic leak. A vacuum test on the valve body once removed can also physically confirm the leak in the SSV bore.
   Typical fix: Replace the entire transmission valve body assembly. Many owners and shops opt for upgraded aftermarket valve bodies from brands like Revmax, Sonnax, BD Diesel, or ATS Diesel, which often feature sleeved SSV bores, billet channel plates, and other enhancements to prevent re-failure. Some specialist shops can ream the original valve body and install an oversized Sonnax valve kit (like part #92835-12) as a more targeted repair.
   Est. part cost: $500-$1600

Rare But Worth Checking

• Damaged Wiring or Connectors: While rare, a damaged wire or a poor connection at the main transmission connector or between the solenoid pack and the TCM can cause an incorrect signal. The TSB S2121000008RevC specifically mentions checking electrical connections as a first step. An open or short-to-ground on the signal wire can be interpreted by the controller as a closed switch.
• Incorrect Check Ball Placement: This applies if the transmission has been recently serviced or rebuilt. For 2019 and newer models, there was a change in the valve body check ball locations. Misplacing a check ball can cause pressure to be applied to the OD switch circuit at the wrong time, triggering P0871.
• Faulty Powertrain Control Module (PCM): This is extremely rare and should only be considered after all other possibilities, including multiple valve body replacements and thorough wiring checks, have been definitively ruled out.
• Loose Spin-On Transmission Filter: → Shop Transmission Assembly There are anecdotal reports of aftermarket spin-on transmission filters coming loose, causing a loss of line pressure that could potentially trigger various codes. Using an OEM Mopar filter is recommended.

Diagnosis Steps

1. Verify the code with a professional-grade OBD-II scanner.
2. Check the transmission fluid level and condition. A burnt smell or dark, metallic color indicates internal clutch damage, suggesting a rebuild may be needed.
3. Scan for other transmission-related codes. The presence of codes like P0734/P0735 is critical for diagnosis and points to a failure beyond just the valve body.
4. Inspect the transmission's main electrical connector for corrosion, pushed-out pins, or damage, as recommended by TSB S2121000008RevC.
5. With a scan tool, monitor the state of the Overdrive Pressure Switch (ODPS) PID while driving. If it shows as 'Closed' or 'On' (near 0 volts) in gears 1, 2, or 3, it confirms a hydraulic cross-leak in the valve body.
6. If the switch operates correctly but the code persists, perform a detailed inspection of the wiring harness between the transmission and the TCM for shorts or open circuits.
7. If wiring is confirmed good and the switch shows incorrect readings, the valve body is the confirmed point of failure. Drop the transmission pan and inspect for excessive clutch material or metal debris, which would indicate the need for a full rebuild.
8. If the valve body is removed, a technician can perform a vacuum test on the solenoid switch valve bore to physically confirm the leak. A minimum of 16 in-Hg is recommended after repair.

Parts You'll Likely Need

• Transmission Valve Body Assembly (OEM #RL033980AC (superseded by 68391407AA)) — This is the root cause of the P0871 code in over 90% of cases due to wear in the solenoid switch valve bore. Replacing the entire assembly is the standard and most reliable repair. The 'RL' prefix indicates a remanufactured part, though they are often new units with anodized bodies to resist wear.
  Trusted brands: Mopar, Revmax, BD Diesel, ATS Diesel, Sonnax
  OEM price range: $500-$900
  Aftermarket price range: $800-$1600
• Transmission Fluid (OEM #68218057AC (Mopar ATF+4)) — The transmission must be drained to replace the valve body, requiring approximately 8-10 quarts for a pan drop and refill. Always use a manufacturer-specified fluid like Mopar ATF+4.
  Trusted brands: Mopar
  OEM price range: $10-$15 per quart
  Aftermarket price range: $8-$12 per quart
• Transmission Pan Gasket and Filter Kit (OEM #5013470AE (Pan Gasket), 68019688AA (Spin-on Filter)) — The pan must be removed for the repair, and the gasket and both filters (sump and spin-on) should always be replaced during this service.
  Trusted brands: Mopar, Wix, ATP
  OEM price range: $60-$90
  Aftermarket price range: $40-$60

Related Codes That Often Appear With This One

• P0700 — This is a generic Transmission Control System Malfunction code that simply indicates the TCM has stored a fault. It will almost always be present alongside a more specific code like P0871.
• P0765 — Underdrive (UD) Solenoid Circuit fault. This code is mentioned in TSB S2121000008RevC as appearing alongside P0871, suggesting a shared hydraulic or electrical issue within the valve body.
• P0755 — 2C Solenoid Circuit fault. Also listed in TSB S2121000008RevC, pointing to a common problem area affecting multiple transmission circuits.
• P0734 / P0735 — Gear 4 or 5 Incorrect Ratio. If these codes are present, it's a very bad sign. It indicates the overdrive clutches are already slipping and damaged due to prolonged low pressure, and a full transmission rebuild will likely be necessary in addition to fixing the valve body.
• P0934 — Line Pressure Sensor Circuit Low. This can appear after installing a high-pressure aftermarket valve body if the system is not properly tuned or if there are other hydraulic issues.

Technical Service Bulletins (TSBs) & Recalls

• S2121000008RevC: Addresses Malfunction Indicator Lamp (MIL) Illumination for DTCs including P0871, pointing towards a known issue with the transmission circuits.

Platform-Specific Known Issues

• TSB S2121000008RevC was issued by the manufacturer for MIL illumination with codes P0871, P0765, and/or P0755, indicating this is a recognized issue that may have electrical or hydraulic causes.
• The 68RFE valve body was updated for the 2019 model year, but the fundamental design and susceptibility to SSV bore wear remain.

Mechanic-Grade Diagnostic Values

• Overdrive Pressure Switch Signal Voltage — expected: System voltage (approx. 5V) in gears 1-3 (switch open).. Failure: Near 0 volts (25-50mV) in gears 1-3, indicating the switch is closed when it should be open.
• Standard Shift Solenoid Coil Resistance (UD, OD, 2C, 4C, LR, MS) — expected: 1.3 Ohms.. Failure: An open circuit or significantly different resistance reading.
• Pressure Control (PC) Solenoid Coil Resistance — expected: 4.9 Ohms.. Failure: An open circuit or significantly different resistance reading.
• Input/Output Speed Sensor Resistance — expected: 535 Ohms at room temperature.. Failure: An open circuit or significantly different resistance reading.
• Valve Body Vacuum Test (Solenoid Switch Valve Bore) — expected: Holds a minimum of 16-18 in-Hg after repair.. Failure: Inability to hold a vacuum, confirming a leak in the bore.

Scan Tool Commands That Help

• AlfaOBD, Autel, Snap-On, wiTECH: Quick Learn / Adaptive Memory Reset — This procedure is mandatory after replacing the valve body or the entire transmission. It allows the TCM to learn the hydraulic characteristics and clutch fill volumes of the new components. Failure to perform a quick learn can result in harsh shifting, persistent codes, or transmission damage.
• AlfaOBD (for 2018+ models): Secure Gateway Module (SGW) Bypass — For 2018 and newer Ram trucks, a secure gateway module prevents aftermarket scan tools from performing bidirectional commands. A physical bypass cable or module is required to allow tools like AlfaOBD to execute the Quick Learn procedure.

Wiring & Ground Locations

• Main Transmission Connector (Solenoid/TRS Assembly) — On the passenger side of the 68RFE transmission case.. This is the main electrical connection for the entire solenoid pack, which includes the Overdrive Pressure Switch. Corrosion or pushed-out pins here can directly cause P0871. Pin 16 is the Overdrive Pressure Switch Sense circuit.
• PCM Connector C4 (NGC) — The Black/Green 38-way connector at the Powertrain Control Module (PCM).. The Overdrive Pressure Signal circuit (often designated T9) runs to this connector. Advanced electrical diagnosis, like checking for continuity or performing a pin-swap test, requires accessing the circuit at this point.

Real Owner Repair Stories

• RamForum.com user (2016 Ram 2500 with 68RFE) — Persistent P0871 code.
  ❌ Tried (didn't work) Replaced the valve body assembly twice.
  ✅ What actually fixed it The issue was still unresolved, but the expert advice given was to perform a pin-swap test. This involves swapping the Overdrive pressure switch circuit with another pressure switch circuit at both the solenoid pack connector and the PCM connector. If the DTC changes to a fault for the other circuit (e.g., P0841 for L/R pressure switch), the wiring is confirmed to be the problem. If P0871 returns, the PCM is the likely culprit, assuming the valve body is good.

OEM Part Supersession History

• RL033980AC, 68033980AC, 52119895AA → 68391407AA — Part number updates and revisions by Mopar. The newest parts are typically anodized to better resist bore wear.
  Heads up: While the parts are physically interchangeable, there are two different sizes of the solenoid switch valve spool (.453" and .420"). Repair kits from Sonnax are specific to the spool diameter in the valve body being serviced, so measurement is required before ordering a reaming kit.

Model Year Variations Within This Range

• 2019-later: Sonnax documentation indicates that some repair kits, like the oversized TCC regulator valve kit 92835-25K, are specifically for 2019 and later 68RFE units, suggesting internal valve body changes around this model year.