Code
P0712
HUMMER
P — Powertrain
Transmission Fluid Temperature (TFT) Sensor Circuit Low Input
Views:
UK: 25
EN: 37
RU: 29
AI status
Completed
Completed
100%
Causes
- Short to ground on TFT signal wire
- Faulty TFT (transmission fluid temperature) sensor
- Poor or corroded connector at the sensor
- Broken/shorted wiring harness between sensor and PCM
- Loss of sensor reference voltage or ground
- Contamination or fluid intrusion at connector
Symptoms
- Check Engine MIL illuminated
- Transmission may shift harshly, erratically, or default to limp mode
- Delayed or incorrect gear changes
- Transmission overheating warning or reduced performance
- Stored freeze-frame data showing abnormal TFT readings
What to check
- Read and record all related codes and freeze-frame data before clearing
- Visually inspect TFT sensor connector and wiring for corrosion, damage or fluid
- Backprobe TFT signal, reference and ground with ignition ON (engine OFF) and note voltages
- Measure sensor resistance (cold) and compare to specification if available
- Wiggle harness while monitoring signal for intermittent change
- Check for continuity to PCM pin and short to ground on signal wire
Signal parameters
- Typical TFT signal: variable voltage within ~0.2–4.8 V depending on fluid temperature (vehicle-specific)
- At cold temps the sensor output is usually higher; at hot temps output trends lower (NTC thermistor behavior)
- Low-input fault = signal voltage below PCM threshold or near 0 V (may indicate short to ground)
- Expect stable reference supply (often ~5 V) and good ground at PCM connector (verify with meter)
Diagnostic algorithm
- Verify: Retrieve freeze-frame and mode 6 data to confirm conditions when P0712 set. Note transmission temperature reading.
- Visual: Inspect TFT sensor connector, pins and harness for corrosion, fluid ingress, damaged insulation or pin push-out.
- Backprobe: With key ON (engine OFF), backprobe TFT signal, reference (often 5 V) and ground. Record voltages. Low signal (near 0 V) with good reference and ground suggests shorted signal or bad sensor.
- Continuity/short check: With battery disconnected, check continuity between TFT signal wire and chassis ground (should not be shorted). Check continuity from sensor connector to PCM pin.
- Resistance test: Remove sensor and measure sensor resistance vs ambient temperature. Compare to factory spec (if available). For NTC type, resistance decreases as temperature increases.
- Wiggle test: Reconnect and start engine (if safe). Monitor live TFT values while wiggling harness and connector to reproduce intermittent faults.
- Repair: Repair damaged wiring, clean/replace connector, or replace sensor as indicated. If sensor and wiring test good and fault persists, consider PCM input diagnosis or replacement per OEM procedures.
- Confirm: Clear codes, drive to run conditions and verify code does not return and TFT readings are plausible.
Likely causes
- Corroded or loose connector at TFT sensor
- Damaged insulation causing signal wire to short to ground
- Failed TFT thermistor (sensor)
- Blown or low reference supply (vehicle-specific)
- Fluid contamination inside connector
Fault status
Status
P0712 — Transmission Fluid Temperature (TFT) Sensor Circuit Low Input: low/near-zero voltage detected on TFT circuit.
Repair difficulty: Medium
Diagnostic time: 0.5 - 2.0 hours
Repair manuals
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