P1185

Code

CADILLAC P — Powertrain

Engine Oil Temperature Circuit

Brand: CADILLAC

Type: P — Powertrain

Views: UK: 34 EN: 50 RU: 38

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Page language: EN

Causes

Open or short in oil temperature sensor circuit
Failed oil temperature sensor (NTC/PTC thermistor)
Poor or corroded connector or wiring damage
Bad ground or reference voltage from PCM
Oil contamination or mechanical fault at sensor
PCM or module fault (less common)

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Incorrect oil temperature gauge or no reading
Transmission shift irregularities or limp mode on some models
Rough cold running or extended warm-up strategy
Stored or pending diagnostic trouble codes related to temperature circuits

What to check

Read freeze frame and live data with a scan tool for oil temperature values
Visually inspect sensor, connector and wiring for damage, oil contamination or corrosion
Check for stored/related codes (coolant/air temp sensor codes) that may indicate wiring harness issues
Verify proper connector seating and secure grounds
Confirm PCM is receiving expected reference voltage (usually 5 V) and has a good ground

Signal parameters

Sensor type: typically thermistor (NTC or PTC) with resistance that changes with oil temperature
Signal range: sensor output to PCM typically 0–5 V (model dependent); expected in-range values usually about 0.5–4.5 V during normal operation
Resistance behavior: NTC decreases with rising temp; expect higher resistance at cold and lower resistance at hot (exact values are model-specific)
Fault indications: open circuit (very high resistance or no voltage change), short to ground (near 0 V) or short to 5 V (near 5 V) or implausible/stuck values over temperature change

Diagnostic algorithm

Retrieve codes and freeze-frame data; note oil temperature reading and related codes.
Visually inspect sensor and harness for contamination, damage or loose connector; repair as needed.
With ignition ON (engine off), measure reference voltage at sensor connector; verify 5 V reference (or manufacturer spec) and good ground.
Measure sensor signal voltage and/or resistance at connector. Compare to manufacturer specification or confirm it changes when warming the engine or applying a heat source (careful with heat tools).
Back-probe connector while monitoring live data with scan tool; confirm PCM sees expected changing temperature values during warm-up.
Check wiring continuity between sensor and PCM for opens/shorts; isolate short to power or ground if present.
If wiring and connector are good and sensor readings are out of spec, replace the oil temperature sensor and retest.
If new sensor still shows fault and wiring is good, perform PCM input circuit tests and consider PCM replacement or reprogramming as last resort.
Clear codes, perform functional test/road test and verify the code does not return.

Likely causes

Damaged wiring harness to oil temperature sensor (chafing, broken conductor)
Corroded or loose sensor connector pins
Sensor internal failure (stuck resistance, intermittent)
Blown fuse or missing 5V reference from PCM
Contamination (oil sludge) preventing proper sensor contact
PCM input circuit fault

Fault status

⚠️ Status

P1185 — Engine Oil Temperature Circuit: PCM detects oil temperature sensor circuit fault (open/short/out-of-range).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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