OBD-II Diagnostic Trouble Code
P0195 — Engine Oil Temperature Sensor
P0195 is a general circuit fault for the engine oil temperature sensor. The ECM sees a signal that is invalid or missing without a more specific range, low or high fault. On heavy diesels the ECM uses oil temperature for engine protection, fan control and fueling or VGT strategies, so a missing value may trigger default behavior.
Severity 2/5
Truck-relevant
Service soon
Severity
Service soon
Engine Oil Temperature Sensor
Code
P0195
Category
Powertrain
Subsystem
Cooling
Truck-relevant
Yes
What this means for truckers
P0195 (Engine Oil Temperature Sensor) — oil temp sensor circuit fault. Modern HD diesels use oil temp to determine oil viscosity and adjust thermal management. Sensor replacement: $50-200. Usually located near the oil filter housing.
Before you replace parts — try this first
P0195 on the Cooling system is most often corroded or loose connector at the oil temperature sensor, often contaminated with oil — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Check-engine light is on. Some diesels show a wrong or missing oil temperature on the dash, or turn on the cooling fan constantly as a precaution. In some protection strategies the engine may derate. Usually there are no mechanical symptoms.
Common causes
- CommonCorroded or loose connector at the oil temperature sensor, often contaminated with oil ($50–$250)
- CommonDamaged wiring between the sensor and the ECM ($100–$400)
- CommonFailed oil temperature sensor, which may be combined with the oil pressure sensor on some engines ($80–$350)
- RareECM fault ($1000–$2500)
How to fix
Read oil temperature live and compare it with coolant temperature after a cold soak.
When to use: First step
Inspect the connector for oil wicking, and check the reference, signal and ground.
When to use: When the reading is missing or fixed
Replace the sensor, using a new seal.
When to use: When the wiring tests good
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0100 — Mass or Volume Air Flow Circuit
- → P0101 — Mass or Volume Air Flow Circuit Range/Performance
- → P0102 — Mass or Volume Air Flow Circuit Low Input
- → P0103 — Mass or Volume Air Flow Circuit High Input
- → P0104 — Mass or Volume Air Flow Circuit Intermittent
Frequently Asked Questions
Can I drive with code P0195?
P0195 is severity 2 — service this week. Not an immediate stop, but ignoring it usually compounds the problem. Most common cause for this code is a worn sensor or minor performance fault that won't strand you today but will get more expensive the longer you wait.
How much does it cost to fix P0195 on a commercial truck?
Total repair cost ranges $50–$2500 depending on the root cause. The cheapest fix is usually the first one listed below — Corroded or loose connector at the oil temperature sensor, often contaminated with oil — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0195 fail a DOT inspection?
P0195 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0195 and related codes?
P0195 is closely related to: P0100 (Mass or Volume Air Flow Circuit), P0101 (Mass or Volume Air Flow Circuit Range/Performance), P0102 (Mass or Volume Air Flow Circuit Low Input), P0103 (Mass or Volume Air Flow Circuit High Input). These codes share the same subsystem (cooling) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0195 is set without the companions, the issue is more isolated.
How do I prevent P0195 from coming back after a repair?
For P0195 (Engine Oil Temperature Sensor), prevention centers on the cooling system. Service cooling system at OEM interval. Use the correct coolant type — modern HD engines need ELC (Extended Life Coolant), not green/conventional. Pressure-test cap and system annually.