P0199

Engine Oil Temperature Sensor Intermittent

P0199 is a generic OBD-II powertrain diagnostic trouble code: Engine Oil Temperature Sensor Intermittent. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0199
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
Need P0199 disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P0199 means

Code P0199 is stored when the powertrain control module (PCM) detects an intermittent or erratic signal from the engine oil temperature (EOT) sensor 'A' circuit. The EOT sensor is a negative-coefficient thermistor that reports oil temperature to the PCM, which uses that data to adjust fuel injection timing, glow-plug operation, idle speed, and oil-temperature warning thresholds. The PCM also cross-references the EOT reading against the engine coolant temperature (ECT) and intake air temperature (IAT) sensors; when those correlations break down due to a signal that randomly drops out or swings outside the plausible range, P0199 is flagged. Because the fault is intermittent rather than hard out-of-range, the PCM typically substitutes a default oil-temperature value and illuminates the MIL without immediately forcing limp mode — though repeated or prolonged dropouts can trigger a failsafe that restricts engine output. Left unaddressed the condition can mask genuine over-temperature events, increasing the risk of accelerated engine wear. The code is generic and applies to all OBD-II compliant vehicles equipped with a dedicated EOT sensor.

Common causes

Most-frequently reported root causes when P0199 is logged.

  • 1
    Corroded, loose, or damaged wiring or connector pins in the EOT sensor harness
  • 2
    Degraded internal thermistor element inside the sensor causing unstable resistance output
  • 3
    Oil sludge or coolant contamination coating the sensor probe and altering its resistance characteristics
  • 4
    Weak or fluctuating 5 V reference voltage supplied by the PCM to the sensor circuit
  • 5
    Poor sensor chassis ground or ground-loop voltage offset
  • 6
    Failed PCM analog-to-digital input channel intermittently misreading the sensor voltage
  • 7
    Intermittent open or short in the signal wire caused by chafing against engine components

Symptoms drivers notice

MIL (check-engine light) illuminated, typically as a soft or pending code initially
Oil temperature gauge fluctuating erratically or reading cold even after full warm-up
Intermittent limp-mode activation when the PCM interprets the erratic signal as a potential over-temperature event
Slightly rough idle or hesitation during engine warm-up while the ECM relies on a substituted default value
Marginally reduced fuel economy on diesel engines where EOT influences injection timing

How to diagnose P0199

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, retrieve all stored codes and freeze-frame data, and note conditions when P0199 was set
  2. 2
    Perform a visual inspection of the EOT sensor connector and harness for corrosion, bent pins, cracking, or chafing against hot surfaces
  3. 3
    Measure sensor resistance at the connector: expect roughly 1,000 Ω cold and 200–300 Ω at operating temperature; a wildly fluctuating reading during a wiggle test confirms an internal fault
  4. 4
    With the ignition on, verify the PCM supplies 5 V reference and a clean ground (less than 0.2 Ω) at the sensor connector
  5. 5
    Monitor live EOT voltage data during engine warm-up; the signal should rise smoothly from ~4 V cold toward ~1 V hot — sudden spikes or dropouts indicate a wiring or connector fault
  6. 6
    Perform a harness wiggle test while observing live data to reproduce the intermittent fault and isolate the affected section
  7. 7
    Replace the sensor only after ruling out wiring and reference-voltage faults; clear codes and confirm repair with a test drive

Related powertrain codes

Frequently asked questions

Can I drive with P0199 active?

Short trips are generally possible because the PCM substitutes a default oil temperature and continues running the engine. However, the failsafe masks real oil over-temperature events, so driving long distances or under heavy load is inadvisable until the fault is resolved.

Will P0199 cause the engine to go into limp mode?

Not always. Most vehicles store the code and illuminate the MIL without immediately restricting power. Limp mode can occur if the PCM interprets repeated erratic spikes as an over-temperature condition, but normal intermittent dropouts usually just trigger the warning light.

Is P0199 the same as P0197 or P0198?

No. P0197 indicates a hard low-circuit fault (sensor reading stuck too cold) and P0198 a hard high-circuit fault (stuck too hot), both of which are out-of-range conditions. P0199 specifically flags an intermittent or erratic signal that randomly falls outside expected parameters rather than holding a fixed extreme value.

How is the EOT sensor different from the ECT sensor?

The engine coolant temperature (ECT) sensor monitors the coolant circuit, while the EOT sensor monitors the engine oil circuit. They often share a similar thermistor design but are located in different places — the EOT is typically threaded into the oil gallery or oil pan. The PCM compares both readings; a large mismatch can trigger additional codes alongside P0199.

Disabling P0199 in software

RaceTune can permanently disable P0199 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECU families we can disable P0199 on

We hold the DaVinci A2L disable definitions for these families, so the exact P0199 path and mask addresses are mapped. verified marks a confirmed disable definition. We support many more — upload your file and our identifier will match it automatically.

  • Bosch EDC17CP44 verified

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

Got P0199 in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file