Volkswagen Golf Transmission Fault
Your automatic gearbox has started behaving strangely, and you’re not sure why. What do you do next?
That was the position Mr P found himself in when his 2020 Volkswagen Golf began skipping gears and failing to engage properly during normal driving. A transmission fault warning had also appeared on the dashboard, making the situation harder to ignore.
The issue had come on without any build-up, and there was nothing to explain it. Mr P was unsure whether the car was safe to keep driving, whether the fault could escalate, and what was actually wrong.
Mr P contacted Fergies in Thatcham for professional guidance. The pattern of symptoms pointed to a Volkswagen Golf transmission fault that needed careful investigation and a reliable resolution.
He needed specialists with the technical capability and a thorough diagnostic approach to uncover the fault and carry out a dependable repair.
With that, Mr P booked the Golf in with Fergies for a full technical evaluation.
Reviewing the Reported Symptoms and Initial Findings
When the Volkswagen Golf arrived at Fergies, Thatcham, our first action was to speak with Mr P and build a complete understanding of the issues he had experienced. We asked about when the irregular gear behaviour had started, how often it was presenting, and whether the symptoms changed depending on driving conditions such as speed, temperature, or the length of the journey.
Taking the time to understand the symptoms thoroughly before testing begins allows our technicians to create an accurate picture of the problem, ensuring that no potential lead goes unnoticed.
Our technicians then performed a road test to confirm the described behaviour first-hand. While driving, manufacturer-level diagnostic equipment was connected to the vehicle, capturing serial data from the transmission control module in real time. This gave our technicians a direct view of how the system was reacting at the exact moment the fault appeared.
A comprehensive system scan was also completed, which flagged a stored fault code directly relevant to the Volkswagen Golf transmission fault:
- P1736 00 — Position sensor for clutch 2, electrical malfunction. Active.
This indicated that the transmission control module had identified an electrical fault connected to one of the internal sensors responsible for clutch monitoring. However, a correct transmission warning light diagnosis means more than noting a code. It means understanding what the code truly represents.
To find out what lay behind the P1736 fault code Volkswagen had logged, and to ensure that the right repair path was chosen, further detailed testing was necessary.
How Did We Pinpoint the Underlying Transmission Issue?
The initial diagnostic scan had revealed fault code P1736, signalling an electrical malfunction related to the position sensor for clutch 2. Before the appropriate repair for this Volkswagen Golf transmission fault could take place, however, our technicians needed to confirm exactly what had failed and establish the reason. A methodical approach was taken, working through each area to build a clear, evidence-led conclusion.
Step 1: Consulting manufacturer technical data
Our technicians used Volkswagen’s technical information service to review the theory of operation for the transmission in Mr P’s Golf.
The 2020 Golf in question was fitted with a seven-speed Direct Shift Gearbox (DSG), a dual-clutch transmission used extensively across the Golf range. Two separate clutches operate within the system: clutch 1 governs odd gears (1, 3, 5, 7) and clutch 2 governs even gears (2, 4, 6, and reverse). A mechatronic unit, which houses both the transmission control unit (TCU) and a hydraulic valve body, manages gear selection and clutch engagement.
Notably, clutch position in this transmission is not detected by a standalone external sensor. The feedback required for clutch control comes from internal pressure sensors within the mechatronic unit, and the system uses those readings to calculate clutch position. When fault code P1736 identifies “position sensor for clutch 2,” it is referring to this integrated pressure sensor inside the mechatronic unit.
This was a key detail, as it indicated to our technicians that the source of the fault was most likely within the mechatronic unit itself, rather than at a separate externally mounted component.
Step 2: Checking for technical service bulletins
Our technicians checked for any relevant technical service bulletins (TSBs) associated with the specific diagnostic trouble code (DTC) and the symptoms being presented.
- A bulletin was found that aligned with both the exact fault code and the behaviour Mr P had reported
- It described this as a known problem with DQ381 transmissions, linked to a fault with the integrated pressure sensors inside the mechatronic unit
- The bulletin outlined how, as these sensors deteriorate or drift outside their calibrated range, the TCU receives inaccurate pressure data and begins miscalculating clutch position, which causes erratic shifting and unreliable gear selection
The TSB reinforced what the P1736 fault code Volkswagen had highlighted, but practical testing was still essential to confirm the fault before proceeding with the repair.
Step 3: Serial data analysis at rest
With the vehicle stationary, the engine off, and the ignition on, our technicians examined the actual pressure values for both clutches using manufacturer-level diagnostic equipment.
- In a system that is functioning correctly, both readings should be as close to 0.00 bar as possible under these conditions
- The reading for clutch 2 showed a measurable deviation from the expected value, consistent with a pressure sensor that had drifted outside its normal operating range
- The reading for clutch 1 was within the expected range, confirming the problem was isolated to the clutch 2 side of the system
These results matched directly with the Volkswagen P1736 fault code and the symptoms Mr P had reported, where the even-numbered gears were the ones being affected.
Step 4: Visual inspection
Our technicians inspected the external condition of the mechatronic unit, wiring harness, and connectors for any signs of damage, corrosion, or compromised connections.
- No external faults were found, ruling out any cause located outside the mechatronic unit itself
The conclusion
With the Volkswagen P1736 fault code now fully explained, the integrated pressure sensor for clutch 2, positioned on the TCU circuit board inside the mechatronic unit, was no longer functioning within specification. It had lost the ability to accurately measure hydraulic pressure for the clutch 2 sub-transmission, causing the system to miscalculate clutch position and resulting in incorrect engagement of the even-numbered gears.
As this sensor is built into the internal mechatronic assembly, it cannot be sourced or replaced as a separate serviceable component. The mechatronic unit needed to be replaced.
Addressing the Volkswagen Golf Transmission Fault with the Correct Repair
After confirming the root cause through detailed testing, our technicians contacted Mr P to share the findings and set out the repair that was required. With his approval in place, the work moved ahead.
Mechatronic unit replacement
- Transmission oil was drained and the mechatronic unit was exposed by removing the transmission oil pan and related components
- The faulty mechatronic unit was disconnected carefully and removed
- The replacement mechatronic unit was installed, and all electrical connections, mounting points, and seals were checked to confirm correct fitment
- Fresh transmission oil was added to the correct Volkswagen specification in accordance with manufacturer procedure
Calibration and adaptation
- Using manufacturer-level diagnostic software, a calibration and adaptation procedure was carried out. This step is critical following mechatronic replacement, as it enables the new TCU to calibrate itself to the existing tolerances of the transmission and clutch mechanics
- All stored fault codes were cleared from the system
Post-repair road test
- A structured road test followed, giving the transmission the conditions it needed to complete its clutch adaptation during real-world driving
- The vehicle was closely monitored to confirm that gear selection was smooth, no gears were being skipped, and no new fault codes were recorded
The Difference After the Volkswagen Gearbox Mechatronic Repair
The Volkswagen gearbox mechatronic repair successfully resolved the Volkswagen Golf transmission fault. The transmission had returned to smooth, consistent operation, and no warning messages were displayed.
By choosing Fergies, Mr P benefited from a detailed, evidence-led technical evaluation that traced and resolved the root cause during the first visit. The automatic transmission fault repair was carried out to manufacturer standards. With access to the same manufacturer technical data and equipment as a main dealership, Fergies provided a first-time fix without the cost associated with a main dealer. A complimentary courtesy car was made available for the duration of the repair, ensuring Mr P’s routine wasn’t disrupted while the work took place.
Mr P left Fergies a happy customer, driving with confidence again.
Experiencing Volkswagen Transmission Issues? Arrange an Expert Inspection with Fergies
If your Volkswagen is changing gear erratically, skipping gears, or displaying a transmission warning message, getting it inspected by specialists is essential. Transmission faults that are left unaddressed can put increasing strain on the gearbox and cause further damage over time.
By choosing Fergies in Thatcham, you benefit from:
- Technicians experienced in diagnosing complex Volkswagen transmission faults
- Access to manufacturer-level technical data, service bulletins, and dealer-level equipment
- A structured, evidence-led technical evaluation process
- More cost-effective repairs than a main dealer
- A complimentary courtesy car to keep you mobile while the work is carried out
- A 12-month parts and labour guarantee for added peace of mind
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If your Volkswagen isn’t performing as it should, call 01635 778002 today.
