Code
P00A9
Generic
P — Powertrain
Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic Bank 2
Views:
UK: 23
EN: 29
RU: 25
AI status
Completed
Completed
100%
Causes
- Damaged or corroded IAT2 connector or wiring (open, short to ground or battery, intermittent contact)
- Failed IAT sensor (thermistor out of tolerance or intermittent)
- Poor ground or power/5V reference to sensor
- Water intrusion or corrosion at connector
- Intermittent PCM/ECM input fault or internal module failure
- Aftermarket components or recent repair damage to harness
Symptoms
- Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
- Intermittent or incorrect intake air temperature displayed in live data
- Poor cold/hot start behavior or rough idle
- Incorrect fuel trims, hesitation, or reduced fuel economy
- Possible failed emissions test or reduced performance under load
What to check
- Retrieve freeze frame and freeze-frame/hlive data for IAT2 and compare to IAT1 and intake air actual temperature
- Monitor IAT2 live data while wiggling wiring and connector to reproduce intermittent behavior
- Visually inspect connector pins and harness for corrosion, bent pins, damaged insulation, or water intrusion
- Check for Technical Service Bulletins (TSBs) or recent software updates for PCM relating to IAT circuits
- Measure reference voltage/pulldown at the harness with key ON (engine OFF) and backprobe sensor connector
- Measure sensor resistance at known ambient temperature (disconnect sensor) and compare to manufacturer spec
Signal parameters
- Sensor type: typically NTC thermistor (resistance decreases as temperature rises)
- Typical electrical behavior: resistance varies with temperature; PCM sees a voltage in the sensor circuit typically in the ~0.1–4.9 V range depending on temp and vehicle design
- Typical resistance order of magnitude: hundreds of ohms at high temps to tens of kilo-ohms at very low temps (example: ~2–5 kΩ around ~20–25 °C on many sensors) — consult vehicle spec for exact values
- Intermittent/erratic fault: rapid, unpredictable changes or jumps in reported temperature, or values stuck at extreme ends
Diagnostic algorithm
- Use a capable scan tool to confirm P00A9 and view freeze-frame/live data for Bank 2 IAT2. Note ambient temp and compare to other sensors.
- With ignition ON (engine OFF) monitor the IAT2 voltage while gently wiggling the wiring and connector to try to reproduce the intermittent reading. Check for connector corrosion or loose pins.
- Visually inspect the harness from sensor to PCM for damage, chafing, or pinched sections. Repair any obvious damage.
- Backprobe the sensor connector: verify reference voltage (if applicable), signal voltage variation with changing air temperature (blow cold/hot air) and good ground continuity.
- Remove sensor and measure resistance across sensor terminals at known ambient temp; compare to vehicle-specific chart. Replace sensor if out of spec or intermittent under bench test.
- Check continuity and resistance of harness between sensor and PCM; repair short to power/ground if present. Check grounds and connector mating surfaces for resistance and corrosion.
- If wiring and sensor test good, test/inspect PCM input circuit and connector. Consider PCM bench test or replacement only after eliminating wiring/sensor faults.
- Clear codes and perform a drive cycle to confirm the fault does not return after repair.
Likely causes
- Dirty/corroded connector or pin causing intermittent contact
- Broken or chafed wiring harness to IAT2 on Bank 2
- Failed IAT2 sensor (thermistor intermittent)
- Loose/poor ground or connector seating
Fault status
Status
Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic — Bank 2. The PCM is detecting unstable or inconsistent IAT2 signal readings which may be caused by wiring, connector, or sensor faults.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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