P0772 code definition
When the Powertrain Control Module (PCM) detects a problems in the shift solenoid, usually in the form of an incorrect gear ratio, a P0772 trouble code is stored. The shift solenoids help to manage the transfer of transmission fluid between the various hydraulic circuits, which in turn cause the transmission to go into different gears. Associated trouble codes include P0770, P0771, P0773, and P0774.
What the P0772 code means
When there is a discrepancy between the gear ratio desired and the actual gear ratio achieved, the PCM stores a P0772 trouble code and the Check Engine Light is illuminated. The particular gear ratio desired is affected by such factors as vehicle speed, engine speed, and throttle position. Mechanics should keep in mind that multiple failure cycles might be required on some models before the Check Engine Light illuminates.
What causes the P0772 code?
Some of the common causes of a P0772 trouble code include:
- Mechanical failure of the transmission
- Blockage within the internal fluid passages of the transmission
- Faulty shift solenoid
- Faulty PCM or Transmission Control Module (TCM)
- Dirty or contaminated transmission fluid
- Low transmission fluid
What are the symptoms of the P0772 code?
Harsh shifting, transmission slippage, or total failure to shift into any particular gear are common signs of a P0772 trouble code. Other symptoms include no obvious symptoms other than an illuminated Check Engine Light and a stored code, overheating of the transmission, and a decrease in the vehicle's fuel efficiency.
How does a mechanic diagnose the P0772 code?
Properly diagnosing a P0772 trouble code requires a mechanic to have an OBD-II scanning tool, a digital volt/ohmmeter, a hydraulic pressure diagram, and a manual pressure pump. The mechanic must also perform the following diagnostic steps:
Start off by pulling the transmission dipstick to examine the transmission fluid. If the fluid looks abnormal or smells burned, the mechanic might have to rebuild the transmission.
To further check the condition of the transmission, remove the transmission pan and inspect it for any debris. If the mechanic finds any debris, the transmission must be rebuilt.
The mechanic should also repair any leaks by filling the transmission to a level sufficient to fix them.
The mechanic should also examine the wiring, connectors, and related components for damage.
Before clearing the codes, the mechanic should fill the transmission fluid to a normal level and download any stored codes and freeze frame data for additional analysis if needed.
The mechanic should then clear the codes before testing the vehicle to system to see if the any of the codes return. The mechanic should do this by starting the vehicle and allowing it to reach a normal operating temperature.
If the code returns upon testing the system, hook up the manual pressure pump to the transmission, and using the hydraulic pressure diagram get an accurate reading of the pressure of the transmission's hydraulic pump, comparing the readings gained to the manufacturer's specifications.
Clear the code and if it returns, and check for the reference voltage and ground signal of the shift solenoid using the digital volt/ohmmeter.
If either the voltage or ground are open, check the continuity and resistance in all related circuits. Make sure to disconnect any related modules, otherwise damage and memory loss can occur.
If everything checks out and the code persists, check the PCM for fault.
Clear the code and test the system to see if the P0772 trouble code or others return.
Common mistakes when diagnosing the P0772 code
A common mistake made by many mechanics when diagnosing this trouble code is to assume the code is caused by a faulty shift solenoid circuit. This leads to the replacement of the shift solenoid which doesn't fix the problem, leading to the return of the code.
How serious is the P0772 code?
The seriousness of a P0772 trouble code ranges from not serious at all to the total failure of the transmission to shift into any particular gear. Vehicle owners also have to be concerned with the decreased fuel mileage that this code can cause.
What repairs can fix the P0772 code?
To fix a P0772 trouble code, the mechanic should perform the following repairs:
- Repair any leaks on the transmission
- Replace the hydraulic pump if it is found to be bad
- Replace the faulty shift solenoid
- Replace the PCM if faulty
- Replace any faulty, damaged, or loose wiring, connectors, or components
- Rebuild the transmission if damaged due to a low fluid condition. The mechanic should also install a new torque converter when doing so.
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