P0685 on Saab: Causes, Symptoms and Fix Cost
Quick Answer
Not safe to drive
P0685 on a Saab 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.
- Severity
- High · Electrical
- Typical repair cost, all makes
- €22-€1200
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Saab 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 Saab?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the Saab models that log P0685.
Saab 9-3 (9440)
2003-2014
Saab's service information (WIS) describes P0685 as a main relay circuit performance problem, set by an open or short circuit on the control module output while battery voltage is between 11 and 18 V. The engine light comes on and the engine may not start. The diagnostic aids say to move the harness to find intermittent breaks and to check connectors for oxidation and retracted pins.
Source: saabwisonline.com
Sources
- saabwisonline.com saabwisonline.com/9-3-9440/2012/dtcs/e39/p0685-00
What causes P0685 on a Saab?
Beyond the generic causes listed on the main P0685 page, these are the patterns noted for Saab models:
Intermittent break or short in the wiring to the main relay
: Saab 9-3 (9440)
Oxidised connector or retracted pin
: Saab 9-3 (9440)
How to diagnose P0685 on a Saab 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 Saab? (EUR)
Estimated repair costs for P0685 in EUR, compiled across makes. Saab costs typically sit in the middle 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