P0870 on 2017-2019 Ram 3500: OD Hydraulic Pressure Fault Causes and Fixes

What's Unique About the 2017-2019 Ram 3500

The key issue for the 2017-2019 Ram 3500 is the critical difference in diagnosing this code between the 66RFE and 68RFE automatic transmissions. For trucks equipped with the popular 68RFE, a Technical Service Bulletin (#9004016) 🎬 Watch: Expert webinar on 68RFE diagnostics and TSB details explicitly warns technicians *not* to replace the solenoid, pressure sensor, or valve body for an isolated P0870 code. The root cause is frequently a software calibration issue that only requires a PCM update. Ignoring this can lead to expensive and unnecessary parts replacement. On the 66RFE, while a software update also exists (TSB #18-040-17 REV. A), the code is more likely to point to a genuine hardware failure.

Diagnostic Flowchart

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

Generation note: The 2017-2018 models are part of the fourth Ram generation, while the 2019 model year began the fifth generation. However, the 68RFE and 66RFE transmissions were common options in both, and the TSBs addressing P0870 cover this entire year range, indicating the issue affects both generations. Notably, the 68RFE was updated in 2019 with changes to the valve body and solenoid pack, which may affect part numbers and repair procedures.

Symptoms You May Notice

• Check Engine Light is on
• Transmission may be stuck in one gear (limp mode), often 4th gear
• Harsh or erratic shifting
• Delayed gear engagement
• Inability to shift into overdrive or use higher gears
• Transmission warning light may be illuminated
• Code returns after 15-20 minutes of driving, especially under load or after accelerating to pass
• Smell of burnt transmission fluid

Most Likely Causes

1. PCM/TCM Software Calibration Issue 🔴 High Probability Manufacturer TSB #9004016 specifically identifies a calibration problem that falsely triggers P0870 on 68RFE transmissions. TSB #18-040-17 REV. A provides a similar software fix for the 66RFE transmission, bundled with other powertrain enhancements.
   How to confirm: A Ram dealer or a qualified shop with a wiTECH scan tool can check your vehicle's current software version against the latest available updates mentioned in the TSBs. This is the mandatory first step for any 68RFE with an isolated P0870.
   Typical fix: Reprogramming (flashing) the Powertrain Control Module (PCM) with the updated software. This is a software-only repair.
   Est. part cost: $0
2. Faulty Transmission Solenoid Pack / Pressure Sensor 🟡 Medium Probability → Shop Transmission Assembly The pressure switch that reports the OD circuit pressure is integrated into the solenoid pack. This assembly is a known failure point on RFE transmissions due to heat, fluid contamination, and internal electronics failure over time. This is a more likely cause on the 66RFE transmission or on a 68RFE after the software update has been performed and the code returns.
   How to confirm: After confirming the software is up-to-date, a technician can monitor the pressure switch data on a scan tool. If the switch doesn't change state when commanded, the solenoid pack is suspect. The solenoids can also be tested for resistance; most should read around 1.3 Ohms, while the pressure control solenoid should be near 4.9 Ohms.
   Typical fix: Dropping the transmission pan and replacing the entire solenoid pack assembly. A fluid and filter change is done at the same time.
   Est. part cost: $350-$600
3. Low or Dirty Transmission Fluid ⚪ Low Probability → Shop Transmission Assembly Incorrect fluid level can cause a variety of pressure-related issues, including low line pressure which can be a factor in setting P0870. While simple, it's a foundational check before any complex repairs.
   How to confirm: Check the transmission fluid level using the dipstick (if equipped) or the proper check-plug procedure. The fluid should be red (for Mopar ATF+4) and not smell burnt or contain excessive debris.
   Typical fix: Top off the fluid to the correct level or perform a full transmission fluid and filter service.
   Est. part cost: $50-$250

Rare But Worth Checking

• Worn Valve Body (Solenoid Switch Valve Bore): → Shop Transmission Valve Body On higher-mileage 68RFE transmissions, the solenoid switch valve (SSV) bore in the aluminum valve body can wear out. This causes an internal hydraulic leak that triggers pressure codes like P0870 and P0871, even with a good solenoid pack. The fix is to ream the bore and install an oversized valve kit, such as the Sonnax 92835-21, or replace the entire valve body. A forum user with a P0871 code was advised this is the likely cause on trucks over 90k miles.
• Damaged Wiring Harness or Connector: Damage to the wiring between the PCM and the main transmission connector can cause an open or short circuit, mimicking a sensor failure. This should be inspected before replacing internal transmission parts. One owner on RamForum.com experienced a P0870 immediately after a transmission replacement, suggesting a wiring or connector issue was likely introduced during the job.

Diagnosis Steps

1. Check for Technical Service Bulletins (TSBs). Using the VIN, confirm with a dealer if TSB #9004016 (for 68RFE) or TSB #18-040-17 REV. A (for 66RFE) applies and has not been performed.
2. If a TSB applies, have a dealer or qualified shop update the PCM/TCM software. This is the most critical and cost-effective first step for 68RFE transmissions.
3. Check the transmission fluid level and condition. Ensure it is full, clean, and does not smell burnt.
4. If the code persists after the software update, use a scan tool to monitor the Overdrive (OD) pressure switch state while driving to see if it changes state as commanded.
5. Inspect the transmission wiring harness and main connector, especially the large round connector at the transmission, for any signs of damage, corrosion, or loose pins.
6. If wiring is good and the sensor data is incorrect, the next step is to replace the transmission solenoid pack, which contains the pressure switch. It is recommended to use a high-quality OEM Mopar part.
7. For high-mileage vehicles (e.g., 90k+ miles) where the code returns after a solenoid replacement, the valve body itself is suspect. Inspect the valve body for wear in the solenoid switch valve bore using a vacuum test. Consider replacing the valve body assembly or having it reamed for an oversized valve kit.

Parts You'll Likely Need

• Transmission Solenoid Pack (OEM #68353383AC (for 2011-2018 models with white plug); 68456067AA (for 2019+ models)) — This is the most likely hardware failure after a software issue has been ruled out. The pressure switch is integrated into this assembly. It's critical to verify the connector color (e.g., white, grey) for pre-2019 models and confirm the model year before ordering.
  Trusted brands: Mopar, Rostra, Suncoast
  OEM price range: $300-$600
  Aftermarket price range: $250-$500
• Oversized Solenoid Switch Valve Kit (OEM #Sonnax 92835-21) — For high-mileage vehicles where the valve body bore is worn, simply replacing the solenoid pack won't fix the internal hydraulic leak. This kit allows for the repair of the valve body itself. Requires special tools to ream the bore.
  Trusted brands: Sonnax, TransGo
  OEM price range: N/A
  Aftermarket price range: $50-$100

Related Codes That Often Appear With This One

• U0101 — Lost Communication with TCM. TSB #18-052-19 REV. A groups P0870 and U0101 together as codes that can be resolved with a PCM software update.
• P2509 — PCM/ECM Power Input Signal Intermittent. TSB #1806120REVA lists this code along with P0870, suggesting a potential electrical or software-related link.
• P0871 — OD Pressure Switch Rationality. This code is very closely related to P0870 and often points to the same root causes, such as a worn solenoid switch valve bore in the valve body. They are often discussed interchangeably in forum threads regarding high-mileage 68RFE issues.

Technical Service Bulletins (TSBs) & Recalls

• 9004016: For 68RFE transmissions, warns against replacing parts for P0870 due to a known calibration issue.
• 18-040-17 REV. A: Provides a software update for the 66RFE transmission that addresses P0870.
• 18-052-19 REV. A: Lists P0870 as a code resolved by a PCM software update.
• 1806120REVA: Also lists P0870 in a group of codes fixed by a software update for 2018 models.

Platform-Specific Known Issues

• TSB #9004016 explicitly states that for Ram trucks with the 68RFE transmission, an isolated P0870 code is likely due to a software calibration issue and that parts like the solenoid, sensor, or valve body should not be replaced until a software update is performed.

Mechanic-Grade Diagnostic Values

• 68RFE Solenoid Coil Resistance — expected: 1.3 Ohms for most solenoids (L/R, 2C, 4C, UD, OD).. Failure: A reading significantly different from 1.3 Ohms suggests a faulty coil.
• 68RFE Pressure Control Solenoid Resistance — expected: 4.9 Ohms. Failure: A reading significantly different from 4.9 Ohms indicates a fault in the pressure control solenoid.
• Pressure Switch State Voltage (at TCM connector) — expected: Open Switch: 12.6-14.4V; Closed Switch: 25-50mV. Failure: Voltage that doesn't change when the circuit is commanded, or readings outside these ranges, points to a wiring or switch fault.
• Valve Body Solenoid Switch Valve (SSV) Bore Vacuum Test — expected: Minimum of 16-18 in-Hg. Failure: A vacuum reading below this threshold indicates wear in the valve body bore, causing an internal hydraulic leak that can trigger P0870/P0871.

Scan Tool Commands That Help

• wiTECH or equivalent professional scan tool: Pressure Switch Test — After confirming software is up-to-date, this bidirectional test commands pressure to individual clutch circuits (like Overdrive) while monitoring the pressure switch status. It helps isolate whether the fault is electrical (switch doesn't respond) or hydraulic (pressure isn't building).
• wiTECH or equivalent professional scan tool: View Event Data / Freeze Frame — This should be an early step to see the exact conditions when the code was set (gear, engine speed, desired vs. actual pressure). This context can help pinpoint the fault.
• wiTECH: PI Curve Relearn — This is a mandatory service function after replacing the valve body or solenoid pack on 2019 and newer models with the updated 68RFE transmission to calibrate the new components.

Wiring & Ground Locations

• Transmission Connector Pin 7 — On the main round electrical connector at the transmission case.. This is the 'Overdrive Solenoid Control' circuit pin. Testing for voltage and continuity at this specific pin is crucial for diagnosing electrical faults between the TCM and the solenoid pack.
• Engine-to-Chassis Ground Strap — Often located from the back of the cylinder head on the passenger side to the firewall or frame.. A poor ground connection for the engine/transmission can cause floating voltages and erratic sensor readings for the entire powertrain, including the transmission sensors, potentially triggering false codes. A visual inspection for corrosion or looseness is a wise step.

Real Owner Repair Stories

• Firepunk Diesel YouTube Channel (Ram truck with 68RFE, 145,000 miles) — P0871 code (OD Pressure Switch Rationality) that would return about 15 minutes after being cleared, eventually forcing the truck into 4th gear limp mode.
  ❌ Tried (didn't work) Clearing the code, which would only provide a temporary fix.
  ✅ What actually fixed it The shop confirmed the software was current. They removed the valve body and performed a vacuum test on the solenoid switch valve (SSV) bore, which failed, confirming an internal leak. The final repair was to ream the valve body bore and install an oversized Sonnax valve kit to restore the hydraulic integrity.

"I Checked Everything" — The Actual Cause

• The equivalent for this code is when the solenoid pack's electrical tests (resistance, continuity) pass, but the code persists. The most common underlying cause is wear in the Solenoid Switch Valve (SSV) bore inside the aluminum valve body. This wear creates an internal hydraulic leak, so the pressure switch never sees the correct pressure, even though the switch itself is functioning perfectly. The leak is invisible from the outside and can only be confirmed by disassembling the valve body and performing a vacuum test on the bore.

When the Usual Fixes Don't Work

• While the TSB for the 68RFE strongly points to a software issue for an isolated P0870, it is not a universal guarantee. On high-mileage trucks (over ~100k miles), wear on the internal valve body bores becomes a much higher probability. As demonstrated in repair stories, if the software flash does not resolve the code, the next logical step is not necessarily the solenoid pack, but rather a vacuum test of the valve body itself to check for wear in the solenoid switch valve bore before replacing any parts.

OEM Part Supersession History

• 68456067AA → 68456067AB — Standard part revision by the manufacturer.
  Heads up: This part is for 2019+ Ram 3500s with the 68RFE only. It is not backward compatible with 2017-2018 models due to a transmission redesign.
• White Connector Solenoid Pack (e.g., 68353383AC) → Grey Connector Solenoid Pack — Design change around 2011.
  Heads up: For 2011-2018 models, the correct part is the 'Grey' connector solenoid pack. The 'White' connector pack can reportedly service all pre-2019 models, but the 'Grey' pack cannot be used on pre-2011 models, making identification critical.

Model Year Variations Within This Range

• 2019 only: The 68RFE transmission was significantly redesigned. It features an added auxiliary valve body, a dedicated TCC control solenoid, and different internal hydraulics. Consequently, the valve body and solenoid pack (PN 68456067AA/AB) are unique to 2019+ models and are not interchangeable with 2017-2018 parts.
• 2019 only: Any replacement of the valve body or solenoid requires a 'PI Curve Relearn' procedure using the wiTECH factory scan tool. This is not a required step for the 2017-2018 models.
• 2017-2018: These models use the 'Grey' connector style solenoid pack, which is different from both earlier 'White' connector packs and the 2019+ design.