Guide To P0A78 OBD Error Code Solutions

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You vehicle will flash codes when there is an issue, the check engine light may also be on in such cases, but don’t worry. You just need to know what that code talks about an accordingly fix it. The P0A78 code is set when the high voltage control module detects a problem with the inverter assembly.

The P0A78 code is a generic OBD-II code. You vehicles inverter converts the high-voltage direct current of the battery as well as the alternating current for MG1/MG2. A three phase bridge circuit is present in the inverter, which also consists of 6 power transistors for each MG1 and MG2. This bridge circuit is present to convert the direct current and the three-phase alternating current. The actuation of the power transistors is done by the ECU. All the information that affects control such as amperage and voltage to the ECU is transmitted by the the inverter. The amperage flow is picked up by the motor inverter current sensors. The inverter transmits this information and the Engine Control Unit monitors the system, any malfunction will cause the ECU to set P0A78 code, and the check engine light will also be turned on.

What causes this problem with the Drive Motor "A" Inverter Performance?

• Fault in the Inverter With Converter Assembly
• Open or shorted Inverter With Converter Assembly harness
• Circuit of the Inverter With Converter Assembly is showing poor electrical connection

1. Inverter with Converter Assembly - Look for repairs and see If the P0A75 code is resolved after fixing the issues, otherwise you will have to replace the inverter with converter assembly.
2. Inverter with Converter Assembly Harness - Repair otherwise replace the harness if the repairs don’t solve the P0A75 code.
3. Engine Control Unit - Try to fix the issues with your ECU through repairs, if that’s not helping, you will have to opt for replacement. Order Online easily at Parts Avatar, simply select the ECU compatible with your vehicle's year of manufacture, make and model and place your order. We ship in just a matter of days!
4. Motor Inverter Current Sensors - Check if you can repair and fix the sensors otherwise go for replacement to get rid of P0A75 error.
5. Powertrain Control Module - Easily replace the PCM from Parts Avatar, order online and avail free shipping on orders above CAD $99, we don’t have any hidden shipping charges in our products, so worry not and order away!
6. Diagnostic Tools - Very important to have the best in hand for diagnosis, At Parts Avatar you can find ones that fit your budget and needs. Order easily from your home and receive your order at your doorstep.

It is helpful to know the symptoms of an issue as only then you would be able to solve the problem. So that’s why we have listed out some major symptoms of OBD Code P0A78 here:

Common Symptoms

• High voltage system may not be operative
• Service engine soon warning light will be on

Below are some ways by which you will be able to correct the OBD Code P0A78

• Repair or replace the damaged wiring, connectors, harnesses and circuits
• Repair or replace High Voltage battery
• Repair or replace the ECU
• Repair or replace the diagnostic tools that aren't working properly

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The diagnosis of P0A78 are not difficult, however it’s important to follow the steps and not sip any of them. If at all you think you won’t be able to do it on your own and need professional help, then feel free to approach a professional vehicle diagnostician for it and resolve your issue properly. However, to solve it you can follow the steps below:

Start off by getting hold of your OBD scanner and connect it to the diagnostic port of your vehicle. Make sure you retrieve all the codes and freeze fame the data also, remember to make note of them all in the order of appearance. If you are able to find any codes set prior to P0A78, then you will have to resolve them first. Previous codes can cause other error codes to set as well, so it’s important that they are taken care of first. After making note of all the codes, clear them and take your vehicle on a test drive to see if the code resets or if the PCM enters readiness more. If the latter happens, then you are having an intermittent condition, this condition may have to worsen before accurate diagnosis can be made. If the code is reset, then you will have to start your diagnosis, the first step is to check all of the electrical system connected with this issue.

Check all the wires, circuits, connectors, harnesses etc. for damages like burning, breaks, corrosion, short etc. If you are able to find any of these issues, simply repair and correct them or opt for replacement. After you have sorted the circuitry you will have to clear the codes and again go on a test drive. Wait to see if the code returns or not (PCM enters readiness mode).If you find that the code is reset, then you will have to check all the parts pertaining to this problem. For this you will require your specific vehicles Technical Service Bulletins or TSB. Match them to the year of manufacture, make, model and engine. Once you have found it, match the symptoms and the error code P0A78 and see what diagnostic steps are mentioned in the TSB. Apart from having diagnostic steps the TSB will also have details of the parts and components related to this error. All the manufacturer specified configurations will also be present. Use the directions given by the TSB to fix your problem, the connector pinout charts, and circuit flow charts etc will be extremely helpful and enable you to avoid any issues with diagnosis.

Common Mistakes When Diagnosing the P0A78 Code

• Skipping steps in the Diagnostic procedure or not following them correctly
• Wrongly Concluding an issue with the ECU when the wires may be damaged and require repairs/replacements

P0A79 - Drive Motor "B" Inverter Performance