Code
P1534
HUMMER
P — Powertrain
A/C High Side Temp. Sensor Low Voltage
Views:
UK: 10
EN: 15
RU: 14
AI status
Completed
Completed
100%
Causes
- Open or shorted sensor wiring (short to ground)
- Corroded, loose or damaged connector at the sensor
- Failed A/C high‑side temperature sensor (thermistor)
- Poor ground or lost reference voltage from the PCM/ECM
- Intermittent harness damage (pinched, chafed)
- PCM/ECM fault or internal driver failure (less common)
Symptoms
- Malfunction indicator lamp (MIL) may or may not be illuminated depending on system
- Reduced or disabled A/C operation, compressor cycling or stuck off
- Incorrect cabin temperature control or poor cooling performance
- Freeze frame or live data shows sensor voltage abnormally low or fixed near 0V
What to check
- Retrieve freeze frame and freeze‑frame data with a scan tool; record live A/C high‑side temp sensor voltage and temperature
- Visual inspection of sensor, connector, and wiring for corrosion, damage, splits, or pinched sections
- Backprobe the sensor connector with ignition ON and A/C requested to observe signal voltage and reference voltage
- Measure sensor resistance (with sensor disconnected) across its terminals and compare to service data or verify it changes with temperature
- Check for good ground at sensor harness and continuity to PCM ground
- Wiggle test wiring while watching live data for intermittent changes
Signal parameters
- Typical reference voltage: about 5.0 V (verify exact value in factory manual)
- Expected sensor signal range: approximately 0.5–4.5 V depending on temperature (thermistor type)
- Open circuit: signal tends toward high impedance or floats (often near reference or 5V); short to ground: signal near 0 V
- Typical thermistor resistance examples (manufacturer specifics required) — verify with service data; resistance should change predictably with temperature
Diagnostic algorithm
- Read and record DTC(s) and freeze frame with a scan tool; note operating conditions when code set.
- Visually inspect sensor, connector, and A/C harness for damage, corrosion, or heat damage; repair obvious issues.
- With key ON (engine off or running per service manual) and A/C request active, backprobe connector: verify reference voltage (≈5V) and good ground at harness. If reference missing, trace back to PCM/fuse.
- Measure sensor signal voltage at connector; if near 0 V suspect short to ground. Wiggle wiring while monitoring for changes.
- Disconnect sensor and measure resistance across sensor terminals at known ambient temperature; compare to factory chart. If out of spec, replace sensor.
- If wiring shows short/open, isolate by disconnecting segments and checking continuity/short to ground; repair or replace harness as needed.
- After repairs or sensor replacement, clear codes and perform A/C function test and road/operational test; confirm DTC does not return.
- If wiring and sensor test good but problem persists, test PCM output/reference and grounds; replace control module only after confirming external circuits are good.
Likely causes
- Wiring short to ground at sensor harness
- Corroded/loose connector at sensor
- Failed temperature sensor element
- Bad ground or missing 5V reference from module
Fault status
Status
A/C High Side Temperature Sensor Circuit — Low Voltage detected. Check sensor, wiring, and reference/ground circuits.
Repair difficulty: Medium
Diagnostic time: 0.5-1.5 hours
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