P0AA5 - OBD Trouble Code

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The trouble code P0AA5 can be defined as Hybrid Battery Negative Contactor Circuit Stuck Open. The hybrid battery negative contactor circuit is being monitored by the hybrid control module. This trouble code would be set by the hybrid control module when the hybrid battery negative contactor circuit would not be as per the specifications set by the manufacturer.

The engine control module, powertrain control module or the transmission control module monitors this circuit depending upon the particular automobile. The high-voltage power supply circuit is connected and disconnected by the system main relays as per the requests from the HV control ECU. There is a total of 3 relays (1 for the negative side and 2 for the positive side) for ensuring a reliable operation. The SMR1 and SMR3 should be turned ON initially for the connection. Then after that the SMR2 would be turned ON and SMR1 would be turned OFF. This process would protect the circuit from the high-voltage surge current by allowing the limit current to flow via the resistor. Then SMR2 and SMR3 should be turned OFF in the same order for disconnecting. It is the HV control ECU which would inspect if the relays have turned OFF properly. The proper functioning of the SMRs (CON1, CON2 and CON3) is monitored by the HV control ECU to inspect the malfunctions.

What causes this problem with the Hybrid Battery Negative Contactor Circuit Stuck Open?

• Malfunctioning system main relay
• System main relay harness might be open or little
• Substandard electrical connection in the system main relay circuit
• The HV control ECU might not be functioning properly

1. Engine Control Module - The solenoid might cause a short in the engine control module because of corrosion in the solenoid or the wire running from the solenoid to the ECM harness. It would be nice if you get it replaced on time.
2. Battery Current Sensor - Most of the time the battery current sensor is faulty and is unable to detect the battery operations properly and thus the reading doesn’t correlate with the temperature sensor readings, causing OBD code P0C45 to get stored in the PCM.
3. Battery Coolant Pump - It is important to understand the functioning and diagnosis of faulty coolant pump as it is the most important component for keeping the battery temperatures under control and keeping it functional all the time. Thus, replace fault battery coolant pump now!
4. Hybrid Battery - The battery itself can be faulty and can be overheating, which can lead to faster discharge and slower charging, with risks of leakages and other damages to the vehicle. Thus, immediate replacement is advisable.
5. Car Battery & Cables - Most of the time it is the cables and connectors that are at fault and are a cheap and easy way to diagnose this error. Thus, replace faulty wiring and connectors immediately.
6. Diagnostic Tool - Make use of quality diagnostic tools to resolve any OBD error code. Buy quality diagnostic tools from us!
7. Battery Temperature Sensor - Temperature sensor measure the battery temperature so that it can be monitored for overheating and other problems in association with the battery. Thus, it is important for the temperature sensor to keep working properly and must be replaced if found faulty.
8. Powertrain Control Module - A trouble with the PCM would mean that it is unable to determine the right fuel mixture and would send the car engine either more or less fuel than it requires. Now when the engine gets more, the carbon emission would increase and fuel economy would drop. In case of the opposite, the engine will choke, stutter, and might start stalling sometimes.

Willing to know some common symptoms of OBD Trouble Code P0AA5? Your wish is our demand. Have a look at them below:

Common Symptoms

• Visibility in the check engine light

If you wish to correct this fault code, then you have to follow certain steps. Correcting a problem needs your careful attention. Here are some ways with the help of which you will be able to correct the OBD Code P0AA5:

• It is essential to restore the flawed system main relay harness
• Repair or replace the quirky system main relay circuit
• Rehabilitate the defaults in the system main relay
• The ECM should be restored to working order
• Recondition the non-functioning HV control ECU

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If you want to easily diagnose this fault code, then all you have to do is to follow the steps which are mentioned below:

A technician begins by hooking the vehicle to an OBD-II scanner to verify that the code is present, and check for other codes. The freeze frame data along with current data is recorded, and the codes are then cleared to see if they reoccur.

Visual inspection of the wiring and connectors to check for loose connections, corrosion, or shorts is done.

A specialized tool may be used to test the hybrid battery negative contactor circuit. Other tests of the hybrid battery negative contactor circuit and its components may help pinpoint the problem, as well as inspection of the wiring and connectors.

Disconnect and check the resistance and signal voltage from the hybrid battery negative contactor circuit. If all the components check out, inspect for the fault in the PCM as it can sometimes store wrong OBD code and thus might need replacement or reprogramming.

Common Mistakes When Diagnosing The P0AA5 Code

• Some issues related to the high voltage control module
• Issues related to the wiring