Code
P1492
PONTIAC
P — Powertrain
Battery Temperature Sensor Voltage Too High
Views:
UK: 13
EN: 49
RU: 22
AI status
Completed
Completed
100%
Causes
- Faulty battery temperature sensor
- Open or shorted wiring (short to B+ or loss of ground)
- Corroded/loose connector or poor pin contact
- Water intrusion or physical damage to harness/connector
- Faulty PCM or reference voltage circuit (rare)
- Aftermarket battery or sensor incorrectly installed
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Incorrect or no battery temperature reading in vehicle data/BCM
- Battery charging or thermal management may operate in a limp or protection mode
- Possible reduced charging performance or charging disabled in extreme cases
- Possible related battery pack warnings/messages on dash
What to check
- Read and record freeze frame and all stored/related codes with a scan tool
- Check live data: battery temperature value and raw sensor voltage/PID
- Visually inspect sensor and wiring harness for damage, corrosion, contamination or poor connections
- Back-probe the sensor connector with ignition ON (engine off) and measure signal voltage, reference (usually 5V) and ground
- Measure continuity and resistance of signal wire between sensor connector and PCM connector; check for short to B+ or short to ground
- Unplug sensor and check harness voltage at harness side to confirm if voltage remains high (isolates sensor vs. wiring/PCM)
Signal parameters
- Typical sensor signal range: ~0.1–4.9 V (varies by application)
- PCM reference voltage typically ~5.0 V; a signal near reference or above the allowed threshold (for example >4.7–4.8 V) usually sets a high-voltage DTC
- Battery temperature sensors commonly use a thermistor (NTC type) — resistance changes with temperature; signal voltage should change when sensor is heated/cooled
Diagnostic algorithm
- Connect professional scan tool; record DTCs and freeze-frame data.
- Monitor live PIDs: battery temperature and sensor voltage while key ON, engine OFF. Note voltage value that triggered the code.
- Visually inspect sensor, connector, and wiring for damage, corrosion, or contamination. Repair as needed.
- Back-probe connector: with connector attached measure signal-to-ground and signal-to-reference voltages. Verify reference supply (≈5V) and ground integrity.
- Unplug sensor and measure voltage at harness side. If harness shows high voltage with sensor disconnected, suspect wiring short to B+ or PCM fault.
- Measure sensor resistance at connector (unplugged) and compare to service specification. Heat or cool sensor to confirm resistance changes with temperature.
- Check continuity between sensor signal pin and PCM pin; check for shorts to battery positive and to ground.
- Repair or replace damaged wiring/connectors. If wiring checks OK and sensor resistance is out of spec, replace the battery temperature sensor.
- After repairs, erase codes, perform functional test/road test and re-scan to confirm code does not return. If wiring and sensor are good but high voltage persists, investigate PCM reference/ground and replace PCM only if confirmed faulty by manufacturer procedures.
Likely causes
- Damaged or failed battery temperature sensor
- Short to battery positive in signal wire or sensor connector
- Corroded/loose connector causing intermittent/high voltage reading
- Broken/shorted wiring between sensor and PCM
- PCM providing incorrect reference/ground (least likely)
Fault status
Status
PCM detected battery temperature sensor circuit voltage above the allowable upper threshold and stored P1492. MIL may be illuminated and battery thermal/charging control may take protective action.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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