Code
P1119
OLDSMOBILE
P — Powertrain
ECT Signal Out Of Range With TFT Sensor
AI status
Completed
Completed
100%
Causes
- Failed or intermittent ECT sensor
- Failed or intermittent TFT (transmission fluid temperature) sensor
- Damaged, corroded or disconnected wiring/connectors between sensors and PCM
- Short to voltage or short to ground in sensor circuit
- Poor sensor/PCM ground or power supply
- Low coolant or transmission fluid level, thermostat stuck, or actual overheating
Symptoms
- Check Engine MIL/SES lamp illuminated
- Incorrect or erratic coolant temperature gauge or temperature PID
- Hard cold/hot starts or poor idle if PCM uses temperature for mixture
- Transmission may shift abnormally if TFT reading is used by TCM
- Possible reduced engine performance or limp mode in some vehicles
- Stored freeze frame data showing abnormal temperature values
What to check
- Read stored codes and freeze frame/live data with a scan tool; record ECT and TFT PIDs and history
- Visual inspection of coolant and transmission fluid level and condition
- Inspect sensor connectors for corrosion, bent pins, water intrusion or damage
- Backprobe sensor connectors and observe voltage/ground/pulses while monitoring live data
- Measure sensor resistance and compare behavior to expected temperature response (NTC sensors: resistance falls as temperature rises)
- Check wiring continuity and for shorts to battery positive or ground between sensor and PCM
Signal parameters
- Sensor voltage range typically 0.1–4.9 V (depends on design); out-of-range = near 0 V or near 5 V or implausible compared to other temps
- ECT/TFT sensors are usually NTC thermistors — resistance decreases as temperature increases
- Expected relationship: ECT and TFT should change gradually and be plausible for engine operating state (e.g., cold engine: low temp readings; warmed engine: higher readings)
- Sudden jumps to full-scale voltage or open-circuit/short-circuit readings indicate wiring or sensor fault
Diagnostic algorithm
- Connect a scan tool, read and record all stored and pending codes and freeze frame data. Note ECT and TFT PIDs and when code set.
- Visually inspect connectors at ECT and TFT sensors and PCM. Repair any corrosion, bent pins, or loose terminals.
- With ignition on (engine off), backprobe the sensor connector(s). Verify reference voltage (if used), signal voltage, and ground presence per factory data.
- Start engine and monitor live ECT and TFT values while engine warms. Look for implausible values, rapid jumps, or a value stuck at extreme.
- Measure sensor resistance at the sensor while ambient/engine at known temperatures. Confirm resistance changes as temperature changes (heat or cool the sensor carefully) and that values respond plausibly.
- Check continuity between sensor connector and PCM connector for shorts or opens. Inspect for short to battery or ground.
- If wiring and connectors check good but signal still out of range, substitute a known-good sensor (or swap equivalent sensors if applicable) to confirm sensor vs wiring/ECM fault.
- Inspect cooling system (coolant level, thermostat) and transmission fluid level/condition; correct as needed and re-test because actual overtemperature or low fluid can trigger comparison faults.
- If all harness, connectors, sensors and fluids are correct and the fault persists, verify PCM power/grounds and consult manufacturer procedures for PCM testing or replacement.
- Clear codes and perform a road/drive cycle to verify repair and ensure the DTC does not return.
Likely causes
- Corroded or loose connector at ECT or TFT sensor
- Open or short in ECT or TFT sensor wiring harness
- Bad ECT sensor (most common)
- Bad TFT sensor or internal short
- Low coolant level or stuck thermostat causing abnormal coolant readings
- Intermittent wiring fault causing out-of-range voltage to PCM
Fault status
Status
ECT signal out of expected range when compared to the Transmission Fluid Temperature sensor input. Possible sensor, wiring/connector, fluid level or PCM-related fault affecting temperature readings.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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