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DTC codes / B01xx · Airbags, seats, doors, lights and comfort systems / B0158

B0158Ambient Air Temperature Sensor Circuit

B0158 indicates the body control module or climate control module has detected an out-of-range signal from the ambient air temperature sensor circuit. The sensor is a thermistor that changes resistance with outside temperature, and the module expects a voltage within a specific range; a reading outside that range for a set time triggers the code.

SystemBody
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

  • Outside temperature display shows dashes, a fixed default value, or an obviously wrong reading
  • Climate control system may default to a fixed temperature strategy or stop automatic air mixing
  • Often no symptoms besides the warning light, especially if the display is not monitored closely
  • Remote start or battery management features that rely on ambient temperature may behave oddly
  • In some vehicles, the radiator cooling fan may run continuously as a failsafe

Common causes, most likely first

  1. Ambient air temperature sensor itself failed or drifted out of specification
  2. Damaged or corroded sensor connector, often from road splash or front-end impact
  3. Broken, chafed, or open wiring between the sensor and the control module
  4. High resistance in a ground circuit shared with the sensor
  5. Control module internal fault on the sensor input circuit
  6. Sensor installed in a location exposed to engine heat or debris, causing skewed readings
  7. Aftermarket accessories or front-end repairs that disturbed the sensor harness

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data to confirm the code is current and not history
  2. Locate the ambient air temperature sensor, usually behind the front bumper or grille, and inspect the connector and wiring for corrosion or damage
  3. Measure sensor resistance with a multimeter and compare to the temperature-resistance chart for the vehicle
  4. Back-probe the sensor signal and ground circuits at the module connector to check for opens, shorts, or excessive resistance
  5. Wiggle-test the harness while watching live data to catch intermittent faults
  6. Replace the sensor if resistance is out of range, then clear codes and verify the temperature display reads correctly
  7. If wiring and sensor are good, test the module input circuit and replace the control module only as a last resort

Why the ambient sensor code misleads

  • A failed ambient air temperature sensor often causes no driveability complaint at all, so many of these codes are found during routine scans rather than by driver report.
  • The sensor is frequently damaged during front bumper removal or collision repair, and the resulting code may not appear until weeks later when corrosion sets in.
  • On some vehicles the ambient temperature reading is shared over a data bus, so a communication fault elsewhere can set B0158 even when the sensor circuit is intact.
  • A sensor that reads plausibly but inaccurately can pass a basic resistance check at room temperature yet still be skewed at cold or hot extremes, so test across the expected temperature range.
  • Replacing the sensor without checking the ground circuit is a common misdiagnosis, because a high-resistance ground shifts the voltage the module sees just like a failed sensor.

Can I keep driving with B0158?

This code does not affect engine operation or safety, so the vehicle can be driven normally. Avoid relying on the outside temperature display or automatic climate functions until the fault is repaired, and address it before any long trip in extreme weather.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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