P0944: Transmission hydraulic pressure lost
Hydraulic pressure unit loss of pressure
Severity: Inspect soon
Kelley Blue Book rates P0944 serious and says it can quickly turn into a problem that leaves you stranded, so it should be inspected soon.
P0944 in short
P0944 means the computer sees the automatic transmission lose hydraulic pressure. Low or dirty fluid, a weak oil pump, a clogged filter, a pressure sensor or a stuck regulator valve can cause it. Ram has bulletins for P0944 with P0868 on the 2023 Ram 3500. Have it inspected soon; it can leave you stranded.
A transmission needs steady oil pressure to apply its clutches. P0944 sets when the computer sees pressure fall well below what it expects, and it may point to the pump losing its prime.
Kelley Blue Book lists low or dirty fluid, a faulty oil pump, a clogged filter, a faulty pressure sensor, a stuck main regulator valve, wiring damage and rarely internal failure. Delayed or no shifting, high rpm and reduced top speed follow.
Ram has two bulletins for the 2023 Ram 3500: SOL S2321000007 covers P0944 (loss of hydraulic pump prime) with P0868 (fluid pressure low), and 9100202 says that with both codes present you should not replace the torque converter or internal parts.
Most likely causes
Cause 1: Low or dirty transmission fluid
Common general cause- Why it ranks here
- Kelley Blue Book lists low or dirty fluid first.
- What would change this
- Rises if fluid is low or dirty. Falls if normal.
Cause 2: Faulty oil pump or clogged filter
Common general cause- Why it ranks here
- Kelley Blue Book lists the pump and filter, and the code description names loss of pump prime on the Ram bulletin.
- What would change this
- Rises if line pressure is low with good fluid. Falls if pressure is normal.
Cause 3: Faulty pressure sensor or stuck main regulator valve
Common general cause- Why it ranks here
- Kelley Blue Book lists both after fluid and pump.
- What would change this
- Rises if the sensor reads wrong against a gauge. Falls if sensor and pressure agree.
Cause 4: Pump assembly and reaction shaft (2023 Ram 3500)
Supported by vehicle data- Why it ranks here
- Ram 9100202 is titled pump assembly and reaction shaft and says with P0944 and P0868 do not replace the torque converter or internal parts; the summary does not state the repair.
- What would change this
- Rises on a covered 2023 Ram 3500 with both codes. Falls on other vehicles.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read all stored codes. Note P0868 (fluid pressure low) stored with P0944.
IfP0944 with P0868 on a 2023 Ram 3500
It meansMatches the Ram bulletins; ask the dealer before any internal repair.
IfOther codes or none
It meansCheck bulletins and fluid.
Step 2: Ask a dealer whether your VIN has a bulletin for P0944.
IfA Ram bulletin applies
It meansFollow it before replacing parts.
IfNo bulletin applies
It meansCheck the fluid.
Step 3: Check the transmission fluid level and condition by the method in the owner's manual. Many transmissions have no dipstick; leave those to a shop.
Warning:Run the check only as the owner's manual describes; the transmission is hot and has moving parts nearby.
IfFluid is low or dirty
It meansFix the leak and service the fluid.
IfFluid is normal
It meansHave line pressure tested.
Step 4: Have a shop check line pressure with a gauge, the filter, and the pressure sensor reading.
Warning:Transmission work involves hot fluid and heavy, moving parts; leave this to a shop.
IfLine pressure is low with good fluid
It meansPump or filter problem is likely.
IfGauge is normal but the sensor disagrees
It meansThe sensor or regulator valve is suspect.
Points to: Faulty pressure sensor or stuck main regulator valve
Symptoms
- Check engine light
- Delayed shifting or no shifting Gets more serious: stop and have it checked.
- Engine rpm higher than normal
- Reduced top speed
How to fix
Step 1: Ask a dealer whether your VIN has an open bulletin for P0944.
On your vehicle
RamYour car
2023 · 3500
Supported by vehicle dataRam S2321000007 and 9100202 cover P0944 with P0868 on the 2023 Ram 3500 and tell dealers not to replace the torque converter or internals. Whether they are still current is not verified.
S2321000007Status unverified
MIL with P0944 loss of hydraulic pump prime and P0868
20233500 · NHTSA 10243164
Names the codes; the summary does not state the repair. Only the NHTSA summary was read.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
9100202Status unverified
Pump assembly and reaction shaft, P0944 with P0868
20233500 · NHTSA 10243098
With both codes present, do not replace the torque converter or internal transmission parts; refer to S2321000007. Only the NHTSA summary was read.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
Sources and review
- P0944 OBD-II Trouble Code: Hydraulic Pressure Unit Loss of Pressure
- Ram SOL S2321000007: MIL with P0944 loss of hydraulic pump prime and P0868
- Ram 9100202: Pump assembly and reaction shaft, P0944 with P0868
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error