P0868 on 2013-2018 Ram 2500 5.7L HEMI: Low Transmission Pressure Causes and Fixes

What's Unique About the 2013-2018 Ram 2500

The 2013-2018 Ram 2500 with a 5.7L or 6.4L HEMI engine uses the 66RFE automatic transmission. While many TSBs for P0868 on Ram HD trucks reference the 68RFE transmission found in Cummins diesel models, the underlying architecture and failure points are very similar as they are both in the RFE family. For both RFE-family transmissions, the line pressure sensor is a known weak point and is integrated into the main solenoid block (also called the solenoid pack or valve body solenoid). Owner experiences frequently highlight that an incorrect fluid level, often from an improper fluid check procedure or a recent service, is the root cause before any parts are replaced. An overfilled condition is particularly common and causes fluid aeration (bubbles), which leads to a drop in pressure.

Symptoms You May Notice

• Check Engine Light is on
• Transmission goes into "limp mode" (may get stuck in 4th gear)
• Harsh, delayed, or erratic shifting
• Inability to shift into higher gears
• Slipping between gears or flaring RPMs
• Transmission overheating warning light
• Hesitation when shifting from Reverse to Drive

Most Likely Causes

1. Incorrect Transmission Fluid Level 🔴 High Probability The fluid check procedure is specific (hot, running, in neutral) and easily done wrong. Both an underfilled and an overfilled condition can cause aeration and pressure issues. Many forum users report this code appearing after a recent service where the transmission was overfilled.
   How to confirm: Check the transmission fluid level according to the manufacturer's procedure: get the transmission to operating temperature (around 180°F), park on a level surface, leave the engine running, shift to neutral, and then check the dipstick. An overfilled level, which can cause bubbles in the fluid, is a very common cause. One owner on RamForum.com found their truck was overfilled by over 3 quarts from the dealer, causing P0868.
   Typical fix: Drain or add Mopar ATF+4 fluid to the correct level. If overfilled, fluid may need to be extracted from the dipstick tube.
   Est. part cost: $15-$60
2. Failed Transmission Line Pressure Sensor 🔴 High Probability The sensor is a known failure point on the RFE transmission family. It provides the pressure reading to the PCM, and a bad sensor will report low pressure even if the actual pressure is fine.
   How to confirm: Use a scan tool to monitor the desired vs. actual line pressure. If the actual pressure reading is erratic, stuck at a low value, or doesn't respond to changes in engine RPM, the sensor is likely faulty. Wiggling the main transmission connector while monitoring the pressure reading can also sometimes reveal a bad connection or failing sensor.
   Typical fix: The sensor is integrated into the solenoid/TRS assembly (solenoid pack). The entire solenoid pack must be replaced. This requires dropping the transmission pan and valve body.
   Est. part cost: $250-$600
3. Clogged or Improperly Installed Transmission Filter 🟡 Medium Probability This is especially common if the P0868 code appears shortly after a transmission service. The primary (sump) filter's O-ring can be cracked, improperly seated, or missing, causing the pump to suck in air instead of fluid, leading to a loss of prime.
   How to confirm: Inspect the transmission pan for excessive debris. Remove and inspect the primary oil filter and its O-ring for cracks, splits, or improper seating. Ensure the filter is fully seated with a positive 'click'.
   Typical fix: Replace the transmission filters (both spin-on and sump filter) and the pan gasket. Ensure the sump filter O-ring is correctly installed and lubricated with transmission fluid before installation.
   Est. part cost: $40-$80

Rare But Worth Checking

• Failing Transmission Oil Pump: If the fluid level is correct and the sensor/solenoid pack has been replaced, the pump itself may be worn and unable to generate sufficient pressure. This is a major internal repair.
• Internal Transmission Leak: A leak in the valve body or from a worn clutch pack seal can cause a loss of line pressure. This usually requires a transmission teardown to diagnose and fix.
• Wiring or PCM/TCM Issue: Though rare, a short or open in the wiring to the pressure sensor, or a fault in the Powertrain Control Module (PCM) or Transmission Control Module (TCM), can trigger this code. A user on Reddit reported a "No Bus" communication error along with P0868, indicating a wider electrical issue.

Diagnosis Steps

1. Verify the transmission fluid level and condition using the correct procedure (engine running, in neutral, at operating temperature). Correct as needed. An overfilled level is a common culprit.
2. Use a quality scan tool to read all transmission-related fault codes. Note if P0868 is active and if P0933 is also present.
3. Monitor the 'Desired Line Pressure' and 'Actual Line Pressure' PIDs on the scan tool while driving. If 'Actual' is consistently more than 15-20 PSI below 'Desired', there is a real pressure problem or a sensor fault.
4. If the code appeared after a recent service, drop the transmission pan and inspect the sump filter and its O-ring for damage or improper installation. This is a very common cause of a suction leak.
5. Inspect the wiring harness and the main round connector at the transmission for any damage, corrosion, or loose pins. Wiggle the connector while monitoring pressure on a scan tool.
6. If the fluid level is correct, the filters are good, and the wiring is intact, the most likely culprit is the line pressure sensor, which is part of the solenoid pack. Replacement of the solenoid pack is the next logical step.
7. If a new solenoid pack does not resolve the issue, the problem is likely a more serious internal issue, such as a failing oil pump or internal seals, requiring professional diagnosis.

Parts You'll Likely Need

• Transmission Solenoid Block / Pack (includes Line Pressure Sensor) (OEM #68224222AA (supersedes 5170877AA)) — The line pressure sensor is the most common electronic part to fail and is integrated into this assembly. It is the primary fix when fluid and filter issues are ruled out. The original part number 5170877AA has been superseded.
  Trusted brands: Mopar, ATP, Rostra, Sonnax (often as an upgrade)
  OEM price range: $450-$600
  Aftermarket price range: $250-$400
• Transmission Filter Kit (Sump and Spin-on) (OEM #5013470AC, 68164325AA) — Required for any service that involves dropping the pan. A clogged or improperly installed filter (especially the sump filter O-ring) is a common cause of the code.
  Trusted brands: Mopar, Wix, ATP
  OEM price range: $60-$90
  Aftermarket price range: $30-$50
• Mopar ATF+4 Automatic Transmission Fluid — The correct fluid type is critical. Low or overfilled fluid is a primary cause of P0868. A pan drop requires approximately 6-8 quarts. Using non-specified fluid can cause damage.
  Trusted brands: Mopar, Valvoline, Castrol
  OEM price range: $12-$18 per quart
  Aftermarket price range: $8-$12 per quart

Related Codes That Often Appear With This One

• P0700 — This is a generic Transmission Control System (TCS) malfunction code that indicates a specific fault, like P0868, has been stored in the transmission control module.
• P0933 — This code specifically relates to a Hydraulic Pressure Sensor Range/Performance issue, which often points directly to a problem with the line pressure sensor itself. Diagnostic procedures often check for P0933 when P0868 is present.

Technical Service Bulletins (TSBs) & Recalls

• 1808022: Mentions P0868 as a possible DTC related to software/calibration issues on 2018 models.
• 1813022REVA: Lists P0868 - Line Pressure Low as a potential code on 2016 models, often alongside other transmission and sensor codes.
• 1806120REVA: Notes P0868 as a possible code on 2018 models.
• 1806120: Cites P0868 as a potential code on 2018 models with the 68RFE transmission.
• 1813022: Lists P0868 for 2016 models, associated with the 68RFE transmission.
• 18-023-21: Includes P0868 as a possible DTC for 2016 models with the 68RFE.
• 1801517: Mentions P0868 as part of a list of codes for 2016 models with the 68RFE.

Platform-Specific Known Issues

• An owner complaint filed with the NHTSA (ODI #11300469) for a 2017 model reported a recurring P0868 code, especially while towing a travel trailer.
• Forum thread on RamForum.com titled 'P0868 solved' where the owner found the transmission was overfilled by 3.25 quarts from the dealer, causing the code. Correcting the fluid level resolved the issue.
• A Reddit thread for a 2016 Ram 2500 with P0868 also experienced a 'No Bus' error when trying to use a code reader, pointing to potential CAN bus or wider electrical issues that can accompany the transmission fault.

Mechanic-Grade Diagnostic Values

• Line Pressure Sensor (LPS) Signal Voltage — expected: 0.35V - 4.75V. Failure: Voltage outside this range will set codes P0934 (low) or P0935 (high), which are related to P0868.
• Scan Tool 'Actual Line Pressure' vs. 'Desired Line Pressure' — expected: Actual pressure should be within 10-15 PSI of desired pressure.. Failure: If actual pressure is consistently more than 15 PSI below desired for 3.5 seconds, code P0868 will set.
• Pressure Control Solenoid (PCS) Resistance — expected: ~4.9 Ohms. Failure: A significant deviation from this resistance indicates a faulty solenoid coil.
• Other Shift Solenoids (LR, MS, UD, OD, 4C, 2C) Resistance — expected: ~1.3 Ohms. Failure: A significant deviation from this resistance indicates a fault in the respective shift solenoid.

Scan Tool Commands That Help

• wiTECH or equivalent professional scan tool: Quick Learn Procedure — This function should be performed after replacing the solenoid pack or valve body. It resets transmission adaptive values and allows the TCM to learn the hydraulic characteristics of the new components, ensuring proper shift quality.
• wiTECH or equivalent professional scan tool: View Transmission CVI (Clutch Volume Index) — To assess clutch health. High CVI values can indicate worn clutches, which may be the root cause of pressure loss. A user reported erratic CVI values that stabilized after fixing a grounding issue, suggesting electrical problems can impact these readings.

Wiring & Ground Locations

• Main Transmission Ground Strap — Typically runs from the transmission bellhousing area to the chassis or engine block. A key ground strap on 4th Gen Rams connects from the frame to the back of the passenger side cylinder head.. A loose or corroded ground can cause a wide range of erratic electronic behaviors, including incorrect sensor readings and shifting problems. One owner found a loose ground strap was the cause of severe shifting issues that varied with A/C usage.
• Main Transmission Harness Connector — The large, round connector on the driver's side of the transmission case.. This is the single point of connection for all electronic signals to and from the transmission. Corrosion or pushed-out pins in this connector can directly cause sensor reading failures and trigger P0868 or related codes.

Real Owner Repair Stories

• RamForum.com user (2016 Ram 2500 5.7L HEMI) — Check Engine Light with code P0868 immediately after purchasing the truck.
  ❌ Tried (didn't work) The owner researched replacing parts before checking the basics.
  ✅ What actually fixed it The owner performed a correct fluid level check (hot, running, in neutral) and found the transmission was overfilled by 3.25 quarts. The fluid also had bubbles on the dipstick, indicating aeration. After removing the excess fluid, shifting improved and the code cleared on its own.
• RamForum.com user (4th Gen Ram with 5.7L HEMI) — Incredibly hard shifting, truck felt like it was 'hitting a brick wall' at 4,500 RPM. Shifting behavior changed dramatically when the A/C was turned on.
  ❌ Tried (didn't work) A dealer-performed 'Quick Learn' procedure only fixed the issue temporarily for about 50 miles.
  ✅ What actually fixed it The owner had found a ground strap on the floor of the truck around the time the issue started. The symptoms pointed towards an electrical/grounding issue, as the electrical load from the A/C compressor clutch engaging changed the transmission's behavior. Re-establishing a solid ground connection is the implied fix.

OEM Part Supersession History

• 5170877AA → 68224222AA, 68353383AC — The solenoid pack for the RFE family of transmissions has been updated multiple times to improve reliability and address common failure points. The updated designs often feature improved materials and construction to prevent circuit board flexing and solenoid failure.
  Heads up: The updated 'white connector' design is generally required for all replacements, especially on earlier models that may have had a gray or black connector.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• The 'HEMI Tick' (Lifter Failure or Exhaust Leak) 🔴 High — Common. Exhaust manifold leak tick is very frequent and may occur under 100k miles. Lifter/cam failure is less common but catastrophic, often appearing after 100k miles.
• Water Pump Failure 🟠 Medium — Common, typically between 60,000 and 150,000 miles.
• Broken Exhaust Manifold Bolts 🟠 Medium — Very common, especially on the rearmost bolts. Can happen at any mileage.
• Electrical System Problems (TIPM) 🟠 Medium — Reported across many model years, but less of a single point of failure than on earlier models.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For a complex and failure-prone electronic part like the 66RFE solenoid pack, buying used from a junkyard is generally not recommended. The risk of getting a part that is already failing or has limited life remaining is high. A used part should only be considered as a last resort if new or remanufactured parts are unavailable and the vehicle is inoperable.

Donor-vehicle mileage cap: roughly under 75000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Verify the donor vehicle's mileage is as low as possible.
• Inspect the connector pins for any signs of corrosion, damage, or being pushed out.
• Ask for a return policy or warranty, as testing the part is impossible without installing it.
• Avoid parts from vehicles that show signs of being in a flood or having significant impact damage near the transmission.

OEM-only on this vehicle (don't cheap out):

• Mopar ATF+4 Fluid: While certified aftermarket equivalents exist, using genuine Mopar fluid eliminates any variables related to fluid compatibility, which is critical in these transmissions.

Aftermarket brands forum-validated for this vehicle:

• Sonnax: Widely regarded in the transmission community for providing high-quality rebuild kits, upgraded components, and complete remanufactured valve bodies/solenoid packs that address known OE weaknesses.
• RevMax: Another popular brand offering performance and heavy-duty replacement parts for the 68RFE/66RFE, including solenoid packs and valve bodies.

Brands owners have reported issues with on this vehicle:

• Unbranded, no-name solenoid packs from online marketplaces should be avoided. Many owners report these failing quickly or being dead-on-arrival. Stick to reputable transmission-specific brands.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0933 — Hydraulic Pressure Sensor Range/Performance — often noted as a code to check for alongside P0868 during the diagnostic process.
• P0869 — Transmission Line Pressure High — the opposite of P0868, often caused by the same faulty line pressure sensor or solenoid pack issues common to the RFE transmission family.
• U0001 — High Speed CAN Communication Bus — related because owners have reported 'No Bus' errors and electrical communication issues when diagnosing P0868.
• P0700 — Transmission Control System (MIL Request) — a general code that often accompanies P0868 to trigger the Check Engine Light when a transmission fault is detected.

Frequently Asked Questions