P00A9

Code

Generic P — Powertrain

Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic Bank 2

Brand: Generic

Type: P — Powertrain

Views: UK: 26 EN: 37 RU: 28

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Page language: EN

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