Volkswagen P1735 Code: Clutch 1 Position Sensor Electrical Fault (DSG)
The DSG control unit lost a valid signal from the sensor that tracks clutch 1 and locks out those gears.
Stop driving
The car usually drives in limp mode on the even gears only, with weak take-offs and no 1st gear. Keep trips short and gentle, avoid highways and steep hills, and book the repair soon, because slipping starts in 2nd gear heat the other clutch.
At a glance
Severity: High
- Meaning
- Clutch 1 Position Sensor Electrical Fault (DSG)
- System
- Transmission · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $50–$4,500
- DIY difficulty
- Professional only
To control a dual-clutch gearbox precisely, the transmission computer needs to know exactly where each clutch actuator is. P1735 (usually shown as P173500, 'clutch 1 position sensor – electrical malfunction') sets when the signal from the clutch 1 sensor is missing or outside its electrical range. On the 7-speed wet-clutch DSG (DQ381) found in later GTI, Golf R, Jetta GLI and Audi A3/S3 models, these sensors sit directly on the control unit's circuit board inside the mechatronic, so there is no external harness to repair; a failed sensor or board is the usual cause. The code is electrical, not a sign that the clutch itself is worn.
How to read P1735
- P Powertrain
- 1 Manufacturer-specific
- 7 Transmission
- 35 Specific fault
Symptoms
- Flashing gear indicator and a transmission malfunction warning
- Car pulls away in 2nd gear, feeling sluggish from a stop
- Odd gears (1st, 3rd, 5th, 7th) locked out; only even gears used
- Code returns immediately after clearing
- Occasional no-drive condition after a restart
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Failed clutch 1 position/pressure sensor on the transmission control unit board
- Transmission control unit fault (solder joints, circuit board damage from heat)
- Fluid or corrosion in the mechatronic electrical connector
- Low system voltage or poor ground during start-up
- Sensor target magnet dislodged or contaminated with metallic debris
Diagnosis step by step
Confirm the exact code and sub-code
Scan the transmission module with a VW-capable tool and note whether P173500 is marked as static (present) or intermittent. Check for the clutch 2 twin code P173600 too; both together strongly suggest the control unit itself.
Tools: OBD-II scanner
Rule out battery and ground problems
Measure battery voltage at rest (about 12.4 V or more) and during cranking (should stay above roughly 10 V). Clean and tighten the battery terminals and the transmission ground, then clear the code and restart; a code caused by a voltage dip will not return.
Tools: Multimeter
Inspect the mechatronic connector
With the battery disconnected, unplug the main connector at the mechatronic and check for fluid, green corrosion or pushed-out pins. Fluid wicking into the plug can distort sensor signals and points to a leaking seal that must be fixed as well.
Tools: Flashlight, Screwdriver
Watch the sensor value in live data
Compare the clutch 1 position or pressure reading with clutch 2 with the engine idling in Park. A reading frozen at a fixed value or jumping to an impossible number confirms the sensor or board, since there is no wiring between them to test.
Tools: OBD-II scanner
Choose control unit repair or mechatronic replacement
A specialist can replace the soldered sensors on the control unit and keep your original coding, which is usually far cheaper than a new mechatronic. After either repair, the shop must run the basic setting and adaptation drive.
Tools: OBD-II scanner
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Clean connector, fix battery or ground issue | Yes | $50–$250 |
| Transmission control unit sensor repair (removal, mail-in or specialist) | No | $600–$1,400 |
| Remanufactured mechatronic unit, installed and adapted | No | $1,800–$3,000 |
| New mechatronic unit at the dealer | No | $2,800–$4,500 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Audi
Audi A3 and S3 with the 7-speed wet-clutch S tronic use the same control unit design, so P173500 and P173600 are handled the same way; repairing the sensors on the board is a common alternative to a full mechatronic.
Emissions / smog test impact
Depends
P1735 is a transmission electrical code that normally doesn't light the check engine light, so most OBD emissions tests will still pass. If the MIL is on for another reason, the vehicle fails until that is repaired.
Frequently asked questions
Is P1735 a clutch wear problem?
No. It is an electrical fault in the sensor that reports clutch 1's position. The clutch may be perfectly healthy; the computer simply can't trust the signal and locks out that half of the gearbox.
Why does my car start off in 2nd gear?
With the clutch 1 sensor unusable, the transmission disables the odd-gear half, including 1st. It runs on clutch 2 and the even gears, which makes launches sluggish and puts extra heat into that clutch.
Can the sensor be replaced on its own?
On the wet 7-speed DSG the sensors are soldered onto the control unit board, so it is not a simple bolt-on part. Specialist shops replace them on the board; otherwise the mechatronic or control unit is replaced.
Will clearing the code fix it?
Only if it was caused by a one-time voltage dip. A static P173500 returns as soon as the transmission checks the sensor again, usually within seconds of starting.
Sources
- Manufacturer public service information (cross-checked)
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