P00DB

Code

Generic P — Powertrain

Ambient Air Temperature Sensor Circuit B Low

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 34 RU: 22

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Page language: EN

Causes

Ambient air temperature sensor (Sensor B) shorted to ground
Failed or internally shorted AAT sensor (B)
Damaged wiring harness (chafing, pinched, water intrusion)
Corroded/loose connector or terminal
Incorrect or poor sensor grounding
Open or poor connection at PCM/module

Symptoms

Ambient outside temperature readout incorrect or pegged low on HVAC/driver info display
HVAC system may behave incorrectly (auto climate control errors)
Possible altered engine cold-start strategies (if vehicle uses AAT for calibration)
Check Engine Light (MIL) or HVAC warning illuminated

What to check

Connect a scan tool; record freeze frame and live data for Ambient Air Temp B
Visually inspect AAT sensor B, connector, and wiring for damage, corrosion, or moisture
Verify vehicle battery voltage is stable during tests
Unplug the AAT sensor connector to see if the code changes (some modules will set an open-circuit code)
Backprobe the sensor circuit at the harness and at the PCM to inspect voltage and continuity

Signal parameters

Sensor type: typically an NTC thermistor (resistance decreases as temperature rises)
Typical reference: 5 V sensor circuit with pull-up resistor (designs vary by OEM)
Expected voltage range (generic): about 0.1 V to 4.9 V across operating temperature range
Circuit-low condition (typical trigger): measured voltage near 0.1–0.3 V (varies by manufacturer)
Typical resistance example (common NTC): ~10 kΩ at 25 °C (specs vary; consult OEM data)

Diagnostic algorithm

Read and record trouble code(s) and freeze frame data with a scan tool. Note ambient temp value shown and PCM status.
Perform a careful visual inspection of the AAT sensor B, connector, and wiring from the sensor to the module. Look for corrosion, bent pins, broken wires, tape/zip-tie damage, or water entry.
With ignition ON (engine off), backprobe the sensor connector and measure sensor circuit voltage to ground. Compare to expected ranges. A reading near 0 V indicates a short to ground or failed sensor.
Measure the sensor resistance (remove sensor if necessary) at known ambient temperature and compare to the sensor specification. For NTC sensors, resistance should be within expected values (e.g., ~10 kΩ at 25 °C—consult OEM).
If voltage is low at the sensor, disconnect the sensor and check if voltage at the harness/PCM side changes. If harness voltage rises when the sensor is unplugged, the sensor is likely shorted.
Check continuity from the sensor signal wire to the PCM pin. Also check for continuity between the signal wire and chassis ground to detect shorts.
Wiggle test the harness while monitoring the live data for intermittent changes. Inspect and repair any damaged sections of wiring or connectors.
If wiring and sensor check good, inspect PCM connector pins for damage/corrosion. If all wiring and connector tests are good and the sensor replacement does not clear the issue, consider module diagnostics per OEM.
After repairs, clear codes, retest, and verify proper ambient temperature readings over a cooldown/warmup or test drive.