For this article, I wanted to cover a repair performed a few months ago on a 2019 Niro EV, showing over 400,000 km on the odometer. Yes, you read that right – 421,000 km!
The customer came to us after noticing that fast charging was either impossible or significantly slower than usual, particularly in cold weather.
Being an electric vehicle, the first step was to read the trouble codes to guide our diagnosis. The code related to this symptom is P1BA5 High Voltage Battery Heating System Circuit High. For this code to be logged, the coolant temperature must have increased less than 2°C after 30 seconds of heater relay activation.
Most EVs have an active battery temperature regulation system to keep it within a range where its performance will be optimal for use. In theory, the diagnostic flowchart for this code should have us specifically check the battery heating system, but Kia being Kia, the flowchart is very general and doesn’t give us much information. In summary, it asks us to check the relay, which is located inside the high-voltage battery. Surely there must be steps we could validate before jumping to something so complex.
A lead to follow. The Kona shares many parts with the Niro, including this code. At Hyundai, we have a bit more information. The flowchart instructs us to activate the heater relay to verify its operation by listening to the relay while simultaneously measuring the coolant temperature change. Indeed, this check confirms it’s not heating, but the relay is working. However, nothing more, and even if we hear the relay, this doesn’t confirm that it has powered the heating element.
The next logical step is to verify that high voltage reaches the element. Using appropriate tools, once the element is disconnected from the high-voltage battery and the interlock circuit completed, we can measure the voltage at the battery output by activating the relay. Nearly 400 Volts. With this measurement, we’ve just confirmed that the relay and fuses inside the high-voltage battery are good, and that replacing the heating element will solve the problem.
Sometimes manufacturers give us limited information about certain components and their operation. But with some comparison, logic, and a well-thought-out strategy, we can repair almost anything!