This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
P0746 is an OBD-II Code refers to Pressure Control Solenoid Performance or Stuck Off detected by the ECM/PCM by an abnormal voltage condition.
A P0746 code is the result of the ECM (Engine Control Module) receiving a signal indicating a problem with the PCS (Pressure Control Solenoid). The PCS controls the pressure of hydraulic fluid in the E-CV (electronic continuously variable transmission) which allows the engine to continue accelerating during throttle kickdown, while keeping vehicle speed constant. With an automated gearbox, hydraulic pressure is varied in order to provide torque converter lockup and shift activation.
Common causes for this code include:
- Faulty pressure control solenoid
- Fluid or debris in the pressure control solenoid
- Open or shorted wiring to the PCS
- Pressure control solenoid failure
- Physical damage of the fluid lines of the PCS
- Internal mechanical failure of the transmission
- Transmission fluid at a low level
- Transmission fluid has been contaminated.
The symptoms of a P0746 code are:
- Changed shift points
- Decreased acceleration (rough idle and/or hesitation)
- Harsh shifting between gears (shuddering or jerking, slipping, bump-pulled gear, rev hang)
- Engine may not downshift into first and overheat
- ETC Failure indicator lit
- Unusual noise or lower acceleration after an upshift
- Poor engine performance and fuel economy
- Unexpected loss of power and low speed torque
To diagnose a P0746 DTC code, an automotive technician would:
1. Verify the code is present using a scan tool.
2. Verify the pressure control solenoid tests based on specific manufacturer specifications for voltage drop and resistance values to determine if there's a problem with the PCS, wiring or connector.
3. Test transmission fluid level by removing the oil pan from the automatic transmission and reading it at its lowest point. If low, fill up with proper fluid as it may be contaminated or burned from abnormal heat created from slipping gears.
4. Check for metallic particles in the fluid as this will indicate physical damage to the valve body of the transmission which could result from an internal mechanical failure of a broken part inside of E-CV slide valve assembly or a defective direct clutch pack on an electronically controlled transmission.
5. Check for signs of fluid leaking from the PCS or from other pressure control solenoids, especially if a decrease in vehicle speed is noted after shifting gears.
The following are common mistakes when diagnosing the trouble code P0746:
- Failing to perform all of the vehicle's tests to determine the root cause
- Confusing the P0746 code with another code such as P0751 or P0753
- Failing to determine other possible factors which may be affecting the performance of the PCS, such as low fluid level, debris in PCS, loose connectors/wiring and defective pressure control solenoids.
- Assuming those driving habits have nothing to do with problems associated with abnormal transmission operation when there are many components that rely on stable oil pressure for normal shifting. Improper use of the accelerator pedal while driving is one example.
How serious is this?
A car with a P0746 trouble code is considered a serious issue, especially if there's low fluid level in the automatic transmission. Without proper oil pressure controls, the vehicle could experience severe damage due to abnormal shifting operation and therefore, will not be drivable. A P0746 code is the result of an out-of-range signal from a PCS which can quickly lead to failure of drivetrain components such as gears and bearings unless stopped in time by the ECM/PCM.
What repairs can fix the code?
The following are solutions that may fix this problem:
- Replacing the pressure control solenoid
- Removing debris or foreign material from the PCS
- Replacing the PCS if it is defective
- Replacing connectors and wiring of the PCS
- Replacing any damaged fluid lines to and from the transmission
- Replacing a broken direct clutch pack assembly, which is used for electronically controlled transmissions.
- Repairing or replacing any internal mechanical damage to the transmission.
A P0746 is related to and may be accompanied by the following codes:
- P0753: Incorrect PCS function (failure)
- P0751: Incorrect 5-6 shift (failure)
- P0750: Computer output state error/transmission control system - no communication to PCM from TCM
- P0758: Transmission fluid over temperature condition
How much does it cost to fix the P0746 code?
The repair cost of a P0746 code may vary depending on the type of transmission, make and model of the vehicle. For example, replacing a defective or malfunctioning PCS is approximately between $160 to more than $1,000. If other components are damaged due to low oil pressure in the automatic transmission system such as gears and bearings, then it can be even higher. Replacing physical transmissions which have broken internal parts will cost several thousand dollars in some cases.
In conclusion, the P0746 is a trouble code that indicates an unusual and unexpected signal from the PCS on an automatic transmission. It can be caused by physical damage to internal parts of the transmission, debris in the system or a defective pressure control solenoid which is used as part of the hydraulic controls for shift scheduling.
A P0746 code can also be triggered by a low fluid level which signals abnormal operation such as slipping gears and burning of fluid due to increased heat production.
There are essential steps that need to be performed for proper diagnosis of this trouble code including checking all wiring and connectors as well as performing all tests associated with the vehicle's operations after noting any symptoms such as sluggish shifting and/or unusual vibration while driving.
Replacing a defective PCS solves most cases but the other transmission components may be also damaged due to low oil pressure which will lead to severe additional expense. If you plan on replacing either or both PCS and/or the ECM/PCM, then you should consult your service professional for assistance to make sure you get all necessary parts at reasonable prices.
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