Code
B1310
HUMMER
B — Body
Ambient Air Temperature Sensor Failure
Views:
UK: 23
EN: 33
RU: 31
AI status
Completed
Completed
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Causes
- Open or short in the ambient air temperature sensor circuit
- Corroded, loose, or damaged sensor connector
- Failed ambient air temperature sensor (thermistor)
- Wiring damaged by abrasion, water ingress, or rodent activity
- Poor ground or intermittent connection
- Control module input fault (rare)
Symptoms
- Ambient temperature display is blank, incorrect, or frozen
- Automatic HVAC may behave erratically or use default settings
- Possible related comfort features (auto defog, remote start) may be affected
- Diagnostic trouble code B1310 stored; MIL may not be illuminated
What to check
- Retrieve freeze frame/live data: note ambient temp sensor reading and related flags
- Visual inspection of sensor location (front bumper/grille) for damage or contamination
- Inspect sensor connector for corrosion, bent pins, moisture, or loose terminals
- Wiggle test wiring with engine/accessory on while monitoring live data for intermittent changes
- Measure sensor circuit voltage/resistance per service manual
- Check for aftermarket parts or recent repairs in the front bumper area
Signal parameters
- Ambient sensor typically is an NTC thermistor; expected signal is a voltage between ~0.5–4.5 V (varies by design) or a resistance that changes with temperature
- Resistance decreases as temperature increases (negative temperature coefficient)
- Exact resistance or voltage vs. temperature values are manufacturer-specific — consult the HUMMER service manual or wiring diagram
- Look for open-circuit (very high/OL resistance) or short-to-ground/short-to-battery (near 0 Ω or heavy constant voltage) conditions
Diagnostic algorithm
- Retrieve B1310 and any related codes; record freeze frame and live ambient temperature reading.
- Visually inspect the sensor (usually mounted behind grille or in bumper) and connector for damage, contamination, or water intrusion. Clean and reseal as needed.
- Backprobe the sensor connector and monitor live data while warming/cooling the sensor by hand or with a heat source (hair dryer) and/or cold spray. Confirm the signal changes smoothly with temperature.
- With ignition off, disconnect sensor and measure resistance across sensor terminals; compare to expected chart in service manual for ambient temperature at the time of test.
- Check continuity between sensor harness connector and the body control/HVAC module pins; inspect for shorts to ground or battery and for high resistance/opens.
- Repair any damaged wiring, terminals, or connector issues. If wiring and connectors are good but sensor resistance/voltage is out of specification, replace the sensor.
- After repair, clear codes, re-test by cycling power and driving/letting sensor reach ambient temperature; verify the ambient reading is plausible and B1310 does not return.
- If code returns after verifying sensor and wiring, consider module input testing per factory diagnostics or consult technical service bulletins.
Likely causes
- Failed/contaminated ambient air temperature sensor
- Connector corrosion or pushed-out terminal at the sensor
- Chafed wiring causing intermittent open/short to ground or battery
- Connector not fully seated after recent service
- Faulty HVAC or body control module input (less common)
Fault status
Status
Ambient Air Temperature Sensor Failure — sensor signal missing, out of range, or implausible. Check sensor, connector, and wiring; replace sensor if out of specification.
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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Repair manuals
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