P078A OBD Error Code: Problem & Solutions

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Is your shift solenoid, TCM, ECM faulty? Do you see the error code P078A? Then you must know what this error code means. This is a general type of error code in most of the vehicles, where the automatic transmission is well prepared. The functionality of the solenoid is monitored and controlled by the transmission control module. If the shift solenoids do not perform well, then the TCM detects then and sets the P078A error code.

The hydraulic pressure in the transmission is controlled by the TCM with the help of shift solenoids so that it can apply clutch packs to provide gear ratios for the vehicle to propel efficiently. Error codes may arise due to mechanical or electrical issues and other stored codes. Improper functioning of the solenoid causes the P078A code to be stored in the vehicle. There can also be a general malfunction in the solenoid or within the circuit.

What causes this problem with the Shift Timing Solenoid A Range/Performance?

• The shift timing solenoid is faulty.
• Automatic transmission fluid is muddy.
• ATF is less.
• ATF passage has blockages.
• Wire harness is defective.
• TCM is faulty.
• ECM is faulty.
• Problem with connectors/pin which is molten, broken or corroded.

1. Shift Solenoid - Are the shift solenoid broken or damaged? Do you find them defective? Then they must be replaced instantly so as to avoid the P078A error code getting stored in the vehicle.
2. Shift Valves - A faulty or defective shift solenoids can cause malfunctioning in the system. Replace them as soon as possible.
3. Engine Light - The engine light illumination may arise if the P078A code is stored. Check them for faults and replace them soon.
4. Transmission Filter - The transmission filter must be free from blockages and debris. Clean them to avoid P078A error code getting stored.
5. Transmission Valve Body - Is this component damaged or broken? Don’t worry, find the right replacement part for transmission valve body from Parts Avatar.
6. Connector - Check the terminals of the connector for damages or if they are broken. If they are defective replace them.
7. Powertrain Control Module - P078A error code may arise due to faulty PCM. Replace them as soon as possible.

We at Parts Avatar Canada care for our customers, and that’s why we will help you to diagnose P078A code by listing out some major symptoms. They are mentioned below as follows:

Common Symptoms

• Jammed gears.
• Irregular shifts.
• Skidding of transmission.
• Rough shifts.
• Shift timing is not productive.
• Drivability issues.
• Acceleration is bad.
• Overall performance is bad.

Learn the ways with which you can correct this trouble code:

• Replacing shift solenoids/ shift valves.
• Clearing blockages in transmission filter.
• Replacing the damaged PCM/ connectors.

However, if you face any issue then we have stocked a wide range of best priced shift solenoid, shift valves, engine light, transmission filter, transmission valve body, connector, wiring, powertrain control module and more to help you out in fixing your car.

It is essential to diagnose this fault code. Here are some steps which a mechanic should follow for diagnosing the problem that triggered a P078A code to be stored:

• Firstly, you have to check the ATF. Replace them if they are muddy, bad odor or has different colors. If you have drove your vehicle for 30,000 to 60,000 miles and don’t remember when you lastly changed liquid, then this can be a problem or even avoiding maintenance schedules can be a problem. A muddy fluid can create blockages and cause this error code in your vehicle.
• The fluid is good and you still see the symptoms? Then you have to access the shift solenoids externally depending on your vehicle make and model. Check the solenoids and wiring harness and connectors for damages or leaks. Replace them if defective and clean the leaky areas.
• Inspect the shift timing solenoid in several ways. One them can be a resistance test where you can measure the resistance with the help of multimeter to check the degree of electrical integrity between the pins in solenoid. Else you can check the manual operation by applying voltage manually to the solenoid. Either of this information will be specified in your service manual.
• Test the TCM circuit. Perform the same test as above and check the functionality of the sensor and circuit by fixing the pins either to TCM/PCM. This is one of the best steps to check the integrity of the solenoid and as well as the circuit.

Common Mistakes When Diagnosing the P078A Code

• Faulty transmission control module.
• Level of fluid in transmission is low.
• Faulty transmission shift solenoid.
• Defective transmission body valve.