Code
P0074
MITSUBISHI
P — Powertrain
Ambient air TEMP.intermittent
Views:
UK: 15
EN: 47
RU: 24
AI status
Completed
Completed
100%
Causes
- Faulty ambient air temperature (AAT) sensor (thermistor)
- Loose, corroded, or damaged connector at the sensor
- Broken, exposed, or shorted wiring/harness to the sensor
- Poor ground or intermittent power/reference to the circuit
- Water intrusion or corrosion at sensor or connector
- Intermittent PCM or body control module internal fault or software glitch
Symptoms
- Intermittent or incorrect ambient temperature displayed in HVAC or instrument cluster
- Automatic climate control may behave erratically (incorrect vent/temperature control)
- Check Engine Light (MIL) may be illuminated or flash intermittently
- Occasional stored freeze-frame or intermittent driveability complaints are unlikely but possible
- Service codes stored after exposure to water or vehicle wash
What to check
- Connect a scan tool and read pending/active codes and freeze frame data
- Monitor live AAT PID while changing ambient conditions (airflow or touching sensor) to see unstable readings
- Visually inspect sensor location, connector, and wiring for damage, corrosion, or water intrusion
- Wiggle test wiring and connectors while observing live data to reproduce intermittent behavior
- Backprobe the sensor connector and measure voltage and/or resistance vs temperature
- Check for applicable Technical Service Bulletins (TSBs) or software updates
Signal parameters
- Sensor type: typically a 2-wire negative-temperature-coefficient (NTC) thermistor (resistance falls as temp rises)
- Expected voltage range at sensor circuit: typically ~0.1 V to ~4.9 V depending on temp and vehicle design
- Expected resistance: decreases with rising temperature — verify against OEM chart if available
- Intermittent code triggers when voltage/resistance fluctuates outside expected range or signal is erratic
Diagnostic algorithm
- Use a scan tool to confirm P0074 is current or pending and note freeze-frame/live AAT values.
- Visually inspect the AAT sensor and wiring harness at the sensor mounting point (look for corrosion, looseness, or damage).
- With ignition ON (engine off), backprobe the sensor connector and observe voltage or measure resistance while comparing to ambient temperature. Verify stable values; consult OEM specs if available.
- Perform a wiggle test: move the wiring and connector while watching live PID for intermittent jumps. Repair any wiring/chafe found.
- If readings are unstable, disconnect sensor and measure open/short to ground and reference. Repair short/open faults and restore proper grounding.
- If wiring and connectors check good, replace the AAT sensor with an OEM or equivalent part and clear codes.
- After repair, recreate conditions and monitor live data to ensure stable readings. Drive or cycle power to confirm code does not return.
- If problem persists with good wiring and new sensor, consider module diagnosis (check for intermittent reference voltage or PCM faults) and consult dealer-level resources/TSBs.
Likely causes
- Corroded connector or water ingress at AAT sensor
- Wiring harness chafe causing intermittent short or open when flexed
- Sensor intermittently out of spec due to internal fault
- Intermittent poor ground or intermittent reference voltage from module
Fault status
Status
Ambient Air Temperature Sensor Circuit Intermittent — control module has detected an intermittent or unstable signal from the ambient air temperature sensor circuit. Inspect sensor, connector, and wiring for intermittent faults.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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