OBD-II Code P0944 — What It Means & How to Fix It

What Does This Error Mean?

P0944 means Hydraulic Pressure Unit Lost Pressure. The automatic transmission's hydraulic system has lost pressure completely or dropped below the minimum threshold. The hydraulic pressure unit (the oil pump and related circuits) is what keeps all gear changes, clutch apply, and torque converter operation working. With no pressure, the transmission may refuse to shift, slip severely, or produce a grinding noise. This is a serious code — stop driving and diagnose immediately.

Affected Models

All automatic transmission vehicles 1996 and newer
Common in Chrysler, Dodge, and Jeep vehicles with 45RFE, 545RFE, and 68RFE transmissions
Common in vehicles with CVT transmissions where hydraulic pressure drives belt clamping
Common in GM vehicles with 4T45E and 6T40 transmissions

Common Causes

Severely low or empty transmission fluid level from a major leak
Failed transmission oil pump unable to build or maintain line pressure
Completely clogged transmission filter starving the pump of fluid
Failed pressure control solenoid causing total loss of regulated pressure
Severe internal seal failure allowing fluid to bypass the pressure circuit

How to Fix It

Stop driving immediately. Check the transmission fluid level. If the fluid is critically low or empty, look for obvious leaks under the vehicle.

A puddle of reddish fluid under the car confirms an active transmission fluid leak. Do not add fluid and drive — find and fix the leak first.
If the fluid level is correct, replace the transmission filter. A completely blocked filter can cause total pressure loss.

Drop the transmission pan — if there is heavy debris or clutch material in the pan, internal damage is likely already present.
Perform a mechanical line pressure test. If pressure reads near zero with correct fluid level and a clean filter, the pump or pressure control solenoid has failed.

A working pump should produce at least 60 PSI at idle. Zero or very low readings confirm pump failure.
Test the pressure control solenoid if the pump produces pressure in isolation but drops under normal operation.

A failed pressure control solenoid can dump line pressure to zero. This is a less expensive fix than pump or rebuild work.
If the pump has failed or internal damage is confirmed, have the transmission removed and inspected by a specialist before authorizing a rebuild.

A teardown inspection determines whether a targeted repair or a full rebuild is the appropriate course of action.

When to Call a Professional

A fluid service with filter replacement costs $150 to $300. Oil pump replacement requires transmission removal — $800 to $2,000. Pressure control solenoid replacement is $200 to $500. If complete internal damage is found, rebuild or replacement is $3,000 to $6,000. Do not continue driving — have it towed for diagnosis.

Frequently Asked Questions

What causes total hydraulic pressure loss?

The most common causes are no fluid (from a leak or improper fill), a completely clogged filter, or a failed oil pump. Severe internal seal failures can also cause total pressure loss. Any of these conditions cause immediate and serious transmission damage if driving continues.

Can I refill the fluid and drive home?

Only if the level was simply low and you found and fixed the leak. If the pump has failed or the filter is completely blocked, adding fluid will not restore pressure. Do not risk driving further — tow it.

Is P0944 fixable without a rebuild?

Sometimes yes. If the cause is low fluid, a clogged filter, or a faulty solenoid, those are fixable without rebuilding. However, a failed pump or internal seal damage requires transmission removal and likely a rebuild or replacement.