Code
P1532
SATURN
P — Powertrain
A/C Evaporator Temperature Sensor Circuit Low Voltage
Views:
UK: 32
EN: 39
RU: 36
AI status
Completed
Completed
100%
Causes
- Short to ground on the evaporator temperature sensor signal wire
- Failed/shorted evaporator temperature sensor (thermistor)
- Corroded, loose or damaged connector or pins at the sensor
- Poor ground or reference supply at the HVAC control module
- Wiring harness damage (chaffing, water intrusion)
- Faulty HVAC/AC control module
Symptoms
- Malfunction Indicator Lamp (MIL) or A/C-related warning and stored DTC
- Reduced or disabled A/C compressor operation
- Erratic cabin temperature control or blower cycling
- HVAC system running in a limp or fail-safe mode
- Possible evaporator freeze / poor cooling performance
What to check
- Scan for P1532 and any related HVAC codes; record freeze-frame and live data
- Visually inspect sensor connector, wiring along firewall/evaporator area for damage or corrosion
- Backprobe sensor connector and measure signal voltage with ignition on and A/C commanded
- Check reference voltage and ground at the sensor connector or HVAC control module
- Measure sensor resistance (thermistor) at ambient and while warming/cooling it by hand/ice to confirm temperature-dependent change
- Perform continuity tests to check for shorts between the signal wire and chassis ground or battery positive
Signal parameters
- Typical evaporator temp sensor signal: about 0.5–4.5 V (varies by design); expect a mid-range voltage near ambient temperature (manufacturer-specific)
- Low-voltage fault threshold commonly below ~0.3–0.5 V (varies by vehicle)
- Thermistor resistance will change with temperature — expect resistance to increase or decrease predictably when warmed/cooled (refer to manufacturer table)
- Reference supply to sensor typically 5 V or a module-supplied pull-up (check vehicle service data)
Diagnostic algorithm
- Retrieve code(s) and freeze-frame data with a scan tool; verify P1532 is current or historic.
- Visually inspect the evaporator sensor connector and wiring for corrosion, pins pushed out, or damage. Repair any obvious issues.
- With ignition ON (engine off) and A/C commanded, backprobe the sensor connector: measure signal voltage, reference voltage (if present), and ground continuity.
- If signal voltage is low, disconnect the sensor and measure for short to chassis ground between the signal wire and ground. Repair any shorted wiring.
- Measure the sensor resistance at ambient temperature and then warm or cool the sensor; confirm resistance changes as a thermistor should. Replace sensor if it does not change correctly.
- If wiring and sensor check good, verify reference/pull-up voltage and ground at the HVAC control module; check for proper operation of the module.
- Repair or replace damaged wiring/connectors/sensor as required. Clear codes and retest system operation and live data to confirm repair.
- If fault persists after sensor and wiring replacement, consider HVAC control module diagnostics or replacement per service manual.
Likely causes
- Shorted signal wire to chassis ground (most common)
- Moisture/corrosion at the sensor connector causing low signal voltage
- Failed evaporator temperature sensor (open/short behavior depending on sensor type)
- Intermittent connector contact or pin pushed out
- Control module fault (least common)
Fault status
Status
A/C evaporator temperature sensor signal is below the expected voltage range. Check sensor, connector, wiring for shorts to ground, and verify HVAC module reference/ground.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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