P0198: Engine Oil Temperature Sensor Circuit High
Quick Answer
Safe to drive (short-term)
P0198 means the engine computer sees a voltage on the oil temperature sensor wire that is higher than a working sensor can produce. It usually points to an open circuit, such as a broken wire, an unplugged connector or a dead sensor, or to a short to the supply voltage. The oil itself is not necessarily hot. The computer then falls back on a fixed oil temperature. On many cars the sensor is a small screw-in part that is cheap to replace; on others it is part of a sump sensor that costs more.
- Severity
- Low · Electrical
- Estimated repair cost
- From €15 to €420+, varies by vehicle
€15 or €420, depending on your car.
- Clean and reseat sensor connector€15–€45
- Replace combined oil level and temperature sensor€135–€420
A scan shows whether P0198 is really stored on your car, which codes sit next to it and how urgent each one is.
A scan needs a Bluetooth OBD2 adapter (Bluetooth LE on iPhone), about €25-60; the built-in demo runs without one. See which adapter to buy
What does P0198 mean?
P0198 is a electrical-related diagnostic trouble code classified as low severity.
What are the symptoms of P0198?
- Check engine light on, usually with no change in how the car drives
- Oil temperature display missing, stuck or showing a strange value
- Oil level reading missing on cars where the same sensor reports level
- Engine functions that use oil temperature, such as injection corrections, working from a fixed value
- Occasional rough running or a changed warm-up pattern on engines that use oil temperature in their maps
What causes P0198?
Open circuit: broken wire, chafed harness or an unplugged connector at the oil temperature sensor
: high
Failed sensor with an open internal element
: high
Connector corroded by water, salt or oil, or with a bent or loose pin
: medium
Short to the supply voltage in the wiring
: low
Poor pin contact in the connector on the engine computer
: low
Faulty engine computer (rare, check the rest first)
: low
Is it safe to drive with P0198?
Generally yes, for short-term driving. Generally safe to drive. The code does not mean the oil is overheating: it means the sensor's signal is out of range, which is usually an open wire or dead sensor. The computer uses a fixed oil temperature instead. Check the oil level by hand while it is stored, because on some cars the same sensor measures oil level, and repair within a few weeks.
How do you diagnose P0198?
- Read the live oil temperature value. A reading frozen at an impossible number on a cold engine, whatever the car shows, suggests an open circuit or dead sensor
- Find the sensor from the service manual, as location differs: some screw into the block, others sit in the bottom of the sump. Inspect the plug and nearby wiring for chafing, oil soaking and corrosion
- Unplug the sensor and check with the key on for the reference voltage from the engine computer on the harness side. No reference voltage means a wiring or computer fault, not the sensor
- Measure the sensor with the plug disconnected. An open circuit reading means a dead sensor. Some combined sump sensors send a digital signal and cannot be tested this way, so use live data
- Check the connector pins at the engine computer end as well, since one bent or oxidised pin can set the code
- Repair the wiring or fit the new sensor, check and top up the oil, clear the code and make sure it stays out over a full warm-up
- Do not chase the oil temperature itself: a high circuit code is about voltage on the wire, not about how hot the oil is
How much does P0198 cost to fix?
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Clean and reseat sensor connector | €0–€5 | €15–€40 | €15–€45 | Easy |
| Replace engine oil temperature sensor (DIY) | €20–€80 | €0–€0 | €20–€80 | Easy |
| Replace engine oil temperature sensor (shop) | €20–€80 | €50–€140 | €70–€220 | Moderate |
| Replace combined oil level and temperature sensor | €55–€220 | €80–€200 | €135–€420 | Moderate |
| Repair sensor wiring or connector | €5–€40 | €50–€140 | €55–€180 | Moderate |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
P0198 on specific vehicles
P0198 on Saab
Saab 9-5 (2.2 TiD diesel) · Saab 9-3 (first generation, 2.2 TiD)
Related diagnostic codes
Common questions about P0198
- What does P0198 mean?
- P0198 means the voltage on the oil temperature sensor circuit is higher than the engine computer expects, which usually means an open circuit or a short to the supply voltage. It is not a sign that the oil is overheating.
- Is my oil overheating?
- Not because of this code. It is an electrical code for the sensor circuit. A real overheating problem shows up in the oil temperature display, the coolant temperature and other warning signs. Check the oil level and condition anyway when the code is stored.
- Can I drive with P0198?
- Yes, in the short term. On the Saab 9-5 2.2 TiD service page the computer substitutes 100 C for the oil temperature while the fault is stored, so the engine still runs. Make sure the oil level is right and book the repair within a few weeks.
- How does P0198 relate to P0196?
- On Saab's 2.2 TiD service pages, the P0196 plausibility check only runs when no P0198 fault is present. When both appear, fix the circuit fault first and check whether P0196 returns.
- What fixes P0198?
- Check the connector and wiring first, then the sensor. The usual fix is a new sensor or a repaired wire. Look at the pins on the computer end as well, because Saab notes that a fault in the control module's connector can trigger the code.
- How much does it cost to fix P0198?
- A screw-in oil temperature sensor costs about 20 to 80 EUR, plus 50 to 140 EUR labour at a shop. A combined oil level and temperature sensor in the sump costs about 135 to 420 EUR fitted, and an oil change is often needed with it.
Read our detailed guides
Sources
- saabwisonline.com saabwisonline.com/9-5-9600/2004/2-engine/psg-16-d223l/fault-diagnosis-diagnostic
- en.wikipedia.org en.wikipedia.org/wiki/Saab_9-5
- saabwisonline.com saabwisonline.com/9-3-9400/2003/2-engine/psg-16-d223l/fault-diagnosis-diagnostic
- en.wikipedia.org en.wikipedia.org/wiki/Saab_9-3