A Hyundai Sonata owner spent thousands of dollars replacing the car’s transmission. Four years later, the same dealership was recommending another major repair. This time, though, the owner wasn’t so sure the dealership had found the problem.
The trouble started when the car suddenly lost power while driving. Warning lights lit up the dashboard, and a message told the driver to check the hybrid system and turn off the engine.
The car, a 2016 Hyundai Sonata Hybrid, was towed to a Hyundai dealership to find out what went wrong. But the diagnosis brought more bad news, leaving the owner with another expensive repair to consider.
To make matters more confusing, an earlier scan had pointed to a possible engine problem. With the dealership recommending something different, the owner turned to Reddit to ask what others thought.
Here We Go Again
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In an October 21 Reddit post, the owner explained that the Sonata had already needed a new transmission in July 2022. The car had about 50,000 miles at the time, and the dealership charged $6,100 to replace it.
Now, roughly 40,000 miles later, the Sonata was back at the same shop. According to the owner, a service adviser said the transmission was slipping and had damaged the hybrid power control unit (HPCU). The dealership recommended replacing both parts.
There was another problem. The owner said the adviser told them the replacement transmission was no longer under warranty because of how many miles had been driven since the 2022 repair.
That meant the owner could be facing another expensive repair on a transmission that had already been replaced once.
A Different Warning
Before the Sonata was towed, a friend scanned it for trouble codes. The result was P1326, which pointed to a possible engine problem rather than directly identifying a transmission fault.
According to a Hyundai technical service bulletin, P1326 is tied to the engine’s knock detection system. It can be triggered when the system detects signs of wear or damage to the engine’s connecting rod bearings. Certain 2016 Sonata Hybrids are included in the bulletin.
When this happens, the car can limit engine power to help prevent more damage. That could explain why the Sonata slowed down while the owner was driving.
The code also came up in a separate Reddit discussion. Someone asked whether P1326 was the only trouble code found, and the owner confirmed it was the only one they knew about.
Of course, finding P1326 doesn’t mean the transmission is fine. But without the dealership’s full test results, it’s hard to know why both the transmission and HPCU needed replacing.
Warranty Questions
The engine warning raised another question: Could Hyundai cover the repair under an extended warranty?
Hyundai has offered extra engine warranty coverage for certain Sonata Hybrid models with connecting rod bearing problems.
A March 2026 Hyundai dealer notice describes engine warranty coverage of up to 15 years or 150,000 miles for certain vehicles with connecting rod bearing problems. An earlier Hyundai service bulletin specifically includes certain 2016 Sonata Hybrids. The owner’s vehicle would still need to meet the program’s requirements.
The extended warranty covers qualifying engine problems. It doesn’t automatically pay for a new transmission or HPCU.
The owner said Hyundai told them the Sonata didn’t qualify for the extended engine warranty. But when they checked the car’s eligibility online, the result suggested otherwise.
According to the owner, no one has explained why the car was excluded.