Random Cutting Out Seat Leon 2014 1.2

[LukeS]

Hi everyone,

I’m having an issue with my 2014 Seat Leon SE Technology TSi Semi-Auto (1.2 Estate, 60,000 miles) and was hoping for some advice.

The Issue:​

A couple of weeks ago, on my way to work, the engine cut out. The accelerator became unresponsive, and there were no revs. The only warning on the dash was a "Brake!" message. After pulling over and restarting, the car drove fine for the rest of the journey (about 30 miles), and again on the way home that evening.

However, the next morning the same thing happened. I restarted the car, but this time the issue returned about 5 miles later, along with an orange engine management light.

Diagnostics:​

I took it to a garage where they couldn’t replicate the issue. Diagnostics showed the following code:

• P084100: Transmission fluid pressure sensor/switch A range/performance.

They told me to monitor the situation. Unsurprisingly, the issue happened again, so I went to a second garage. They found the same code as well as:

• U010300: Lost communication with gear shift module
• B10ABF0: Refrigerant pressure below lower limit

I was referred to a gearbox specialist, who explained that the transmission fluid pressure sensor is part of the mechatronics unit and recommended replacing the entire unit, quoting around £2000. However, they weren't confident that this is related to the engine cutting out. They suggested another garage with "dealer-level" diagnostics for VAG software updates.

Next Steps:​

Another transmission specialist also believes the mechatronics unit might be causing the issue and gave me a similar quote.

Questions:​

1. Has anyone experienced similar issues with their Seat Leon?
2. Is it worth replacing the mechatronics unit, or should I seek further diagnostics for software updates or other potential causes?
3. Any other suggestions for dealing with this problem?

Note: The issue seems to happen randomly, both at speed (55-60mph) and in slower traffic or while stopping at junctions.

Any advice would be greatly appreciated as I’m not very mechanically inclined, and I want to avoid unnecessary costs if possible.

Thanks in advance!

 

[queen]

I can only recommend something for the lost communication part. Have a mechanic/specialist check if the connector on the dsg is fully plugged in or maybe if it has a bend pin as that could cause this issue.

 

[LukeS]

Quick update now that the car’s fixed:

The Problem:​

After posting, things actually got worse while the car was in the garage. It even started struggling to go into reverse. The main issue turned out to be with the mechatronics unit. Apparently, a cracked plate inside can cause a loss of transmission pressure, leading to erratic power loss and gear engagement issues.

The Fix:​

The garage replaced the mechatronics unit, which resolved the main issues. They also found crimped wires in the electrical harness that had been interfering with error signals reaching the OBD port, which is why initial diagnostics didn’t pick up all the codes. Once those were fixed, the diagnostics were more accurate.

Key Points for Anyone with Similar Issues:​

• Mechatronics Unit: If you’re experiencing intermittent power loss or gear issues, a failing mechatronics unit could be the cause. Cracks or internal pressure issues can affect the DSG transmission's performance.
• Wiring Check: If diagnostics aren’t pulling up many error codes despite problems, consider checking the electrical harness for any damaged or crimped wires.
• Dealer-Level Diagnostics: Going to a garage with dealer-level diagnostics for VAG vehicles can make a difference, especially with complex transmission issues like these.

Hopefully, this helps anyone dealing with similar problems!