P0964 Pressure Control Solenoid "B" Control Circuit/Open

The P0964 trouble code is an OBD-II diagnostic trouble code associated with the electronic and hydraulic control system of an automatic transmission.

P0964 – Pressure Control Solenoid “B” Control Circuit/Open

This code means that the transmission control module (TCM) or powertrain control module (PCM) has detected an open or interrupted electrical circuit involving Pressure Control Solenoid “B.”

In simple terms, the transmission computer is trying to control Pressure Control Solenoid “B,” but it detects that the electrical circuit is not complete or current is not flowing as expected.

The problem can be caused by a failed solenoid, broken wire, disconnected connector, loose terminal, corrosion, damaged internal transmission wiring or, less commonly, a problem with the TCM.

What Does P0964 Mean?

P0964 – Pressure Control Solenoid “B” Control Circuit/Open

Automatic transmissions use electronically controlled solenoids to regulate hydraulic pressure.

The TCM sends electrical commands to these solenoids based on operating conditions such as:

• Engine RPM

• Vehicle speed

• Throttle position

• Engine load

• Transmission temperature

• Selected gear

• Torque demand

• Driving conditions

Pressure Control Solenoid “B” regulates hydraulic pressure within a specific transmission circuit.

When the TCM detects that the electrical circuit controlling this solenoid is open or interrupted, it can store P0964.

A simplified operating sequence is:

TCM command → Electrical circuit → Pressure Control Solenoid “B” → Hydraulic pressure → Transmission operation

If the electrical path is interrupted, the solenoid may not respond to the TCM's commands.

What Is a Pressure Control Solenoid?

A pressure control solenoid is an electrically operated hydraulic valve.

It regulates transmission fluid pressure according to commands from the TCM.

Depending on the transmission design, it may control:

• Main line pressure

• Clutch pressure

• Shift pressure

• Torque converter pressure

• A specific hydraulic circuit

The solenoid allows the TCM to electronically adjust transmission pressure rather than relying solely on mechanical or hydraulic control.

What Does the “B” Mean?

The “B” identifies a particular pressure-control solenoid according to the manufacturer's transmission design.

It does not necessarily mean that it is physically the second solenoid in the transmission.

Different transmissions use different solenoid layouts and naming conventions.

Pressure Control Solenoid “B” may be located:

• Inside the transmission

• Inside the valve body

• In a mechatronic assembly

• On a transmission control assembly

The exact location and function should always be confirmed using vehicle-specific service information.

What Does “Circuit/Open” Mean?

The word “Open” is particularly important with P0964.

An open circuit means that the intended electrical path is interrupted.

For example:

TCM → Wiring → Transmission connector → Internal wiring → Solenoid

If the wire is broken anywhere along this path, the circuit may become open.

The same situation can occur if:

• A connector is disconnected

• A terminal has poor contact

• A terminal has backed out

• A wire is corroded

• The solenoid coil has an internal break

The TCM can then detect that the expected electrical response is missing.

Does P0964 Mean Pressure Control Solenoid “B” Is Bad?

Not necessarily.

A defective solenoid is one possible cause, but P0964 specifically indicates an open electrical circuit.

The actual problem could be located anywhere in the circuit.

Possible causes include:

• Broken wiring

• Disconnected connector

• Loose terminal

• Corroded terminal

• Damaged internal transmission harness

• Open solenoid coil

• Poor electrical connection

• TCM circuit failure

Therefore, replacing the solenoid without checking the wiring and connectors may not solve the problem.

Symptoms of P0964

Symptoms depend on the transmission design and the function of Pressure Control Solenoid “B.”

Possible symptoms include:

• Check Engine Light

• Transmission warning light

• Harsh shifting

• Delayed gear changes

• Erratic shifting

• Transmission slipping

• Increased engine RPM

• Poor acceleration

• Delayed Drive engagement

• Delayed Reverse engagement

• Transmission stuck in one gear

• Limp mode

• Reduced fuel economy

Some vehicles may continue driving relatively normally.

In those cases, the Check Engine Light may be the only noticeable symptom.

Common Causes of P0964

There are several possible causes of this code.

Broken or damaged wiring

Transmission wiring is exposed to:

• Heat

• Vibration

• Moisture

• Transmission fluid

• Oil

• Road contamination

Over time, wiring can become damaged.

Possible problems include:

• Broken conductors

• Chafed insulation

• Pinched wires

• Melted insulation

• Corrosion

• Poor previous repairs

Disconnected transmission connector

If the transmission connector is not fully seated, the TCM may lose the electrical connection to Pressure Control Solenoid “B.”

This can happen after:

• Transmission repair

• Valve-body work

• Transmission replacement

• Fluid service

• Harness work

Loose or damaged terminals

A connector can be physically connected while the electrical connection remains unreliable.

Possible problems include:

• Loose terminals

• Bent pins

• Backed-out terminals

• Corrosion

• Damaged connector locks

Faulty Pressure Control Solenoid “B”

The solenoid coil itself may have an internal open circuit.

In this situation, the external wiring can be perfectly intact while the solenoid fails to conduct electricity.

Corrosion

Moisture and transmission-fluid contamination can damage electrical terminals.

Corrosion can increase resistance and eventually interrupt the circuit completely.

Internal transmission wiring problem

Some transmissions use an internal wiring harness to connect the external transmission connector to the solenoids.

A failure in this internal harness can trigger P0964.

TCM fault

The TCM controls the solenoid circuit electronically.

A failure in the TCM's internal driver circuit can potentially produce a solenoid circuit fault.

However, the TCM should generally be considered only after the solenoid, wiring and connectors have been tested.

Can Low Transmission Fluid Cause P0964?

Low transmission fluid does not normally cause P0964 directly.

P0964 is primarily an electrical circuit/open code.

Low transmission fluid can cause:

• Low hydraulic pressure

• Transmission slipping

• Delayed engagement

• Erratic shifting

But low fluid does not normally create a broken electrical circuit.

The fluid level should still be checked because low fluid may cause separate transmission problems.

Can Dirty Transmission Fluid Cause P0964?

Dirty transmission fluid can cause:

• Solenoid sticking

• Valve-body contamination

• Restricted passages

• Hydraulic pressure problems

However, contaminated fluid does not normally create an electrical open circuit.

If P0964 is present, the electrical circuit should be inspected carefully.

P0964 vs. P0965 vs. P0966 vs. P0967

These codes are closely related but describe different conditions.

P0964 – Pressure Control Solenoid “B” Control Circuit/Open

The electrical circuit is open or interrupted.

P0965 – Pressure Control Solenoid “B” Control Circuit Range/Performance

The circuit or solenoid operation is outside the expected performance range.

P0966 – Pressure Control Solenoid “B” Control Circuit Low

The TCM detects an electrical condition lower than expected.

P0967 – Pressure Control Solenoid “B” Control Circuit High

The TCM detects an electrical condition higher than expected.

This distinction is important.

When P0964 is stored, the diagnostic process should place particular emphasis on continuity, connectors, terminals, internal wiring and solenoid-coil integrity.

How Serious Is P0964?

P0964 can be relatively simple or potentially serious.

A broken wire, loose connector or damaged terminal may be repaired without major transmission work.

However, if Pressure Control Solenoid “B” controls an important hydraulic circuit, its failure can significantly affect transmission operation.

Possible consequences include:

• Harsh shifting

• Incorrect clutch pressure

• Transmission slipping

• Excessive heat

• Limp mode

• Accelerated internal wear

For this reason, P0964 should not be ignored.

Can You Drive With P0964?

If the vehicle shifts normally and there are no severe symptoms, a short drive to a repair facility may be possible.

However, prolonged driving with an unresolved transmission-control problem is not recommended.

Driving should be minimized if you experience:

• Severe transmission slipping

• Violent gear changes

• Loss of Drive

• Loss of Reverse

• Transmission overheating

• Limp mode

• Burning transmission fluid smell

These symptoms can indicate a more serious transmission problem.

How to Diagnose P0964

Because P0964 indicates an open circuit, the diagnostic process should concentrate on the complete electrical path between the TCM and Pressure Control Solenoid “B.”

1. Scan the TCM

Use a professional diagnostic scanner to retrieve all stored and pending codes.

Look for additional faults involving:

• Pressure-control solenoids

• Shift solenoids

• Transmission pressure sensors

• Transmission temperature

• Gear ratios

• Communication

• Power supply

If multiple solenoids show circuit faults, a shared electrical problem may be more likely.

2. Check freeze-frame data

Review the conditions under which P0964 was stored.

Useful information may include:

• Engine RPM

• Vehicle speed

• Transmission temperature

• Selected gear

• Throttle position

• Solenoid command

• Transmission operating mode

This can help determine whether the problem is permanent or intermittent.

3. Identify Pressure Control Solenoid “B”

Use the vehicle-specific wiring diagram to identify:

• Solenoid location

• Connector pinout

• Power supply

• Control wire

• TCM connection

• Internal transmission wiring

Do not assume that Pressure Control Solenoid “B” has the same location on every transmission.

4. Inspect the external wiring

Look for:

• Broken wires

• Chafed insulation

• Pinched wiring

• Melted insulation

• Corrosion

• Poor previous repairs

Pay particular attention to the wiring around the transmission and exhaust.

5. Inspect the transmission connector

Check for:

• Bent pins

• Loose terminals

• Backed-out terminals

• Corrosion

• Water intrusion

• Transmission fluid contamination

• Damaged connector locks

A connector may look properly connected while one of its terminals has poor contact.

6. Check circuit continuity

With the appropriate connectors disconnected, test continuity through the Pressure Control Solenoid “B” circuit.

Compare the results with the manufacturer's specifications.

An open reading can indicate:

• Broken wire

• Disconnected terminal

• Internal harness problem

• Connector failure

Always follow the manufacturer's specified testing procedure.

7. Measure solenoid resistance

Measure the resistance of Pressure Control Solenoid “B.”

Compare the result with the manufacturer's specification.

If the meter shows OL/open circuit where a measurable resistance should exist, the solenoid coil may be internally open.

Do not use a generic resistance specification because different transmissions use different solenoids.

8. Check for excessive resistance

A wire may not be completely broken but can still have excessive resistance.

Possible causes include:

• Corrosion

• Damaged conductor strands

• Poor terminal contact

• Improper repairs

Voltage-drop testing can help locate these problems.

9. Check internal transmission wiring

If the external wiring and connectors are good, the internal transmission harness may need to be inspected.

Depending on the transmission, this may require removing:

• Transmission pan

• Valve-body components

• Mechatronic assembly

The manufacturer's service procedure should be followed.

10. Check the TCM circuit

If the solenoid and wiring are confirmed to be good, the TCM output circuit can be tested according to manufacturer specifications.

The TCM should not be replaced simply because P0964 is present.

Why P0964 Can Be Difficult to Diagnose

A permanent open circuit can be relatively easy to locate.

An intermittent open circuit is much more difficult.

The fault may appear only when:

• The transmission is hot

• The vehicle is moving

• The harness vibrates

• The engine or transmission moves under load

• A connector changes with temperature

• The vehicle travels over bumps

A wire can therefore test normally when the vehicle is stationary and fail during a road test.

P0964 After Transmission Repair

If P0964 appears immediately after transmission repair or replacement, inspect the components disturbed during the repair.

Possible causes include:

• Connector not fully seated

• Bent connector terminal

• Pinched harness

• Disconnected internal wiring

• Damaged solenoid connector

• Incorrect harness routing

• Damaged wiring during transmission removal

If the code appeared immediately after transmission work, the repair area should be inspected carefully before assuming that the transmission has suffered internal damage.

P0964 After a Transmission Fluid Change

A transmission fluid change does not normally cause an electrical open-circuit code.

However, if P0964 appeared after service, inspect:

• Transmission connector

• Wiring harness

• Solenoid connections

• Internal transmission wiring

• Connector contamination

If the transmission pan or valve body was removed during service, the internal solenoid connections should be checked carefully.

Can P0964 Cause Limp Mode?

Yes.

Depending on the transmission design, the TCM may activate a protective operating strategy when it detects that Pressure Control Solenoid “B” cannot be controlled.

The vehicle may:

• Remain in a particular gear

• Use only a limited number of gears

• Shift harshly

• Increase line pressure

• Delay engagement

• Restrict transmission operation

Not every vehicle with P0964 will enter limp mode.

The exact response depends on the transmission and control software.

Can P0964 Damage the Transmission?

P0964 does not automatically mean that internal transmission damage has occurred.

However, if the solenoid is responsible for controlling clutch pressure, an electrical failure can result in incorrect hydraulic operation.

Continued driving may increase:

• Clutch wear

• Heat

• Hydraulic stress

• Internal component wear

If the transmission is slipping or shifting violently, continued driving should be avoided.

Common Diagnostic Mistakes With P0964

One of the most common mistakes is immediately replacing Pressure Control Solenoid “B.”

The actual problem may be a broken wire or poor connector.

Another common mistake is checking only the external harness.

Some transmissions have internal wiring harnesses that can fail.

Another mistake is assuming that a connector is good simply because it is plugged in.

A terminal can be loose, corroded or pushed backward inside the connector.

Replacing the TCM too early is another mistake.

P0964 does not automatically mean that the TCM is defective.

The wiring, connectors and solenoid should be tested first.

What Is the Correct Repair for P0964?

The correct repair depends on where the open circuit is found.

Possible repairs include:

• Replacing Pressure Control Solenoid “B”

• Repairing a broken wire

• Replacing damaged wiring

• Repairing a loose terminal

• Replacing a damaged connector

• Removing corrosion

• Repairing internal transmission wiring

• Correcting connector installation

• Repairing the solenoid control circuit

• Repairing or replacing the TCM when conclusively diagnosed as faulty

After the repair, the diagnostic codes should be cleared and the vehicle should be tested under the conditions in which the fault originally occurred.

Final Thoughts on P0964

P0964 – Pressure Control Solenoid “B” Control Circuit/Open indicates that the transmission control module has detected an open or interrupted electrical circuit involving Pressure Control Solenoid “B.”

Unlike P0965, which indicates a range/performance problem, P0964 points more directly toward an interruption in the electrical circuit.

The most important areas to inspect are the wiring harness, connectors, terminals, internal transmission wiring and Pressure Control Solenoid “B” itself.

Low transmission fluid and contaminated fluid can cause transmission performance problems, but they do not normally create an electrical open circuit.

A proper diagnosis should begin by identifying the correct solenoid and circuit, followed by connector and wiring inspection, continuity testing and solenoid resistance testing. If these components are confirmed to be good, the TCM control circuit can then be investigated.

P0964 does not automatically mean that the transmission needs to be rebuilt or replaced. Finding the exact point where the electrical circuit is interrupted can often prevent unnecessary solenoid, TCM or transmission replacement.