Code
P1397
GM
P — Powertrain
Wheel Speed Sensor 2 G-Sensor Circuit Low Voltage
AI status
Completed
Completed
100%
Causes
- Open or high-resistance wiring between sensor and control module
- Corroded, loose or damaged sensor connector or pins
- Failed wheel speed (G) sensor
- Short to ground on the sensor signal wire
- Damaged or missing reluctor/ tone ring or excessive air gap
- Faulty ABS/PCM/BCM module (rare)
Symptoms
- ABS warning light illuminated
- Traction/stability control warning or disabled
- Inoperative or erratic speedometer or cruise control (depending on vehicle)
- Possible intermittent ABS activation or no ABS when expected
- Diagnostic trouble code P1397 stored; possible related codes
What to check
- Read freeze frame and live data for wheel speed sensors with a scan tool
- Visually inspect sensor, connector, wiring harness, and reluctor/tone ring
- Check connector pins for corrosion, bent pins or poor mating
- Backprobe sensor signal and ground with ignition on to verify reference and ground
- Measure sensor output while spinning the wheel (multimeter or oscilloscope)
- Perform continuity and resistance checks on signal and ground wires to the module
Signal parameters
- Active Hall-type sensor: 5 V reference present; signal typically a square wave 0–5 V (or ~0.5–4.5 V) with speed
- Passive/VR sensor: AC voltage that increases with wheel speed (low-speed values may be
- Typical fault indication: signal stuck near 0 V (low) or no AC output on passive sensor
- Ground should be
Diagnostic algorithm
- Use a scan tool to confirm P1397 and review freeze-frame/live sensor data to verify low-voltage condition and identify affected wheel.
- Visually inspect the sensor, connector and wiring at the wheel for damage, corrosion, contamination or loose mounting.
- With ignition ON (engine off), backprobe the connector: verify reference voltage (if applicable), signal line voltage, and ground continuity to the module.
- Spin the wheel by hand or raise vehicle (safe support) and measure sensor output: passive sensor shows AC voltage increasing with speed; active shows switching/pulse voltages. Use an oscilloscope if available for best signal view.
- Check for continuity and shorts: measure resistance/continuity from sensor connector to ABS/module pins and check for short to ground or battery.
- Inspect the reluctor/tone ring and air gap; repair or replace if damaged, bent, missing teeth or excessively corroded.
- If wiring, connector or mounting issues are found, repair or replace damaged harness/connector, clean contacts, and secure sensor properly.
- If wiring and reluctor are good but signal still low, replace the wheel speed sensor with a correct OEM-type part and retest.
- After repair, clear codes, perform a road test while monitoring live data to confirm normal sensor outputs and that P1397 does not return.
- If code remains after sensor/wiring replacement and proper signal verified, test or consider replacing the ABS/PCM/BCM module or consult manufacturer service info for module-level diagnostics.
Likely causes
- Corroded connector at the wheel hub or module
- Broken/ chafed signal wire under vehicle or in suspension travel path
- Sensor contaminated with metal debris, grease or brake dust
- Reluctor ring teeth damaged, missing, or covered in rust
- Bad ground at the module or sensor ground circuit
- Aftermarket or incorrect replacement sensor with wrong output type
Fault status
Status
Low voltage detected on Wheel Speed Sensor 2 (G‑Sensor) circuit — inspect sensor, wiring, connectors, reluctor and module.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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