P0685 on Volkswagen: Causes, Symptoms and Fix Cost
Quick Answer
Not safe to drive
P0685 on a Volkswagen means the engine computer (ECM/PCM) monitors the circuit that switches its main power relay and found it open or without the expected voltage. On many cars the relay feeds power to the computer, injectors and ignition, so when it does not close the car often will not start. The fault can be the relay, its fuse, a corroded socket, damaged wiring, or low battery voltage, and only rarely the computer itself. VW, Audi, Skoda and SEAT apps often show this code as P068500; the last two digits are a failure-type byte.
- Severity
- High · Electrical
- Typical repair cost, all makes
- €22-€1200
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Volkswagen and Skanyx tells you what P0685 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0685 mean on a Volkswagen?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the Volkswagen models that log P0685.
VW Jetta 2.5 (North American market) and City Golf
2005-2007
Ross-Tech's wiki ties P0685 to a faulty ECM relay (J271) or a voltage supply problem to the engine computer, with MIL on and no start. For the 2005 to 2007 2.5L Jetta it says to check the red/black ECM power wire, where damage can sit about 15 to 45 cm (6 to 18 inches) from the connector, and for the Canadian City Golf with the BEV engine to check a corroded splice powering a wire to the ECM. These engines were sold mainly in North America.
Source: wiki.ross-tech.com
Sources
- wiki.ross-tech.com wiki.ross-tech.com/wiki/index.php/17069/P0685
What causes P0685 on a Volkswagen?
Beyond the generic causes listed on the main P0685 page, these are the patterns noted for Volkswagen models:
Faulty ECM relay J271
: VW Jetta 2.5 (North American market) and City Golf
Damaged power wire to the ECM near the connector
: VW Jetta 2.5 (North American market) and City Golf
Corroded splice feeding the ECM power wire
: VW Jetta 2.5 (North American market) and City Golf
How to diagnose P0685 on a Volkswagen with OBD2
- Test battery voltage at rest and while cranking before anything else. Low voltage can switch the relay off or make the computer reset.
- Find the engine computer relay and its fuses in the wiring diagram. Remove the relay and check the socket for green or white corrosion, bent contacts and water marks.
- Swap in a known-good relay of the same type and test again. If the code has gone and the car starts, the relay was the fault.
- Measure the relay coil supply and the control side with the ignition on. The computer pulls the control wire to ground when it wants the relay closed.
- Check the fuse with a meter, not by eye. If it blows again at once, there is a short that must be found before another fuse is fitted.
- Look for wiring damage between the relay carrier and the engine computer connector, especially near moving parts, harness bends and where water can sit.
- Check power and ground pins at the engine computer connector under load.
- Replace the computer only after relay, fuse, wiring and ground have been proven good.
How much does P0685 cost to fix on a Volkswagen? (EUR)
Estimated repair costs for P0685 in EUR, compiled across makes. Expect Volkswagen parts and labour towards the upper end of each range.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace ECM/PCM power relay | €30–€100 | €10–€40 | €40–€140 | Easy |
| Replace blown ECM fuse after finding the short | €2–€15 | €20–€80 | €22–€95 | Moderate |
| Repair relay socket or wiring to the ECM | €10–€60 | €80–€250 | €90–€310 | Moderate |
| Battery replacement | €60–€200 | €20–€60 | €80–€260 | Easy |
| Replace ECM/PCM with programming | €250–€900 | €100–€300 | €350–€1200 | Professional |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0685
These codes are often seen alongside P0685 or point to related issues, on any make:
Looking for the full P0685 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0685 guide