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DTC codes / GM codes / P1398

P1398 · GMWheel Speed Sensor 2 G-Sensor Circuit High Voltage

This code means the body control module (BCM) or electronic brake control module (EBCM) has detected an abnormally high voltage on the signal circuit of wheel speed sensor 2, which on many GM vehicles also incorporates a lateral G-sensor used for stability control. The computer expects the sensor's output to stay within a specific voltage window, and a reading above that window for a set time triggers the code.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaIgnition system and misfire

Symptoms you may notice

  • Anti-lock brake system (ABS) warning light illuminated on the dashboard
  • Traction control or stability control (StabiliTrak) warning light on, often with a message in the driver information center
  • ABS and stability control systems disabled, though normal braking usually remains
  • Speedometer may fluctuate or read incorrectly if the affected sensor also provides a wheel speed signal
  • Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

  1. Damaged or chafed signal wire shorted to voltage or to a 12-volt source along the harness
  2. Corroded, loose, or water-intruded connector at the wheel speed sensor or the module
  3. Failed wheel speed sensor or G-sensor assembly, particularly after impact or bearing service
  4. Debris or metallic particles stuck to the sensor tip or tone ring, causing an erratic high-voltage signal
  5. Faulty ABS/ESC control module or BCM, though this is less common and should be confirmed last
  6. Aftermarket electrical accessories tapped into the sensor circuit, introducing stray voltage

How to diagnose and fix it

  1. Inspect the wheel speed sensor and its connector at the affected wheel for corrosion, water intrusion, or physical damage, and clean or replace the connector as needed
  2. Check the sensor signal circuit for a short to voltage using a digital multimeter with the key on and the sensor disconnected, looking for battery voltage on the signal wire
  3. Inspect the harness routing for chafing against suspension components or the wheel well, and repair any exposed or shorted wires
  4. Measure the sensor's internal resistance and compare it to the GM specification for that axle; replace the sensor if it is open or out of range
  5. Clear the code and perform a road test with a scan tool watching the wheel speed and G-sensor live data to confirm the signal is stable and within range
  6. If the signal remains high with a known-good sensor and verified wiring, test the ABS/ESC module ground and power feeds, then substitute a known-good module only after all other tests pass

Why a G-sensor code often isn't the sensor

  • On many GM vehicles, wheel speed sensor 2 is shared with the lateral G-sensor function, so a high-voltage fault can be set by a shorted harness rather than a failed sensor, and technicians who replace the sensor first often see the code return.
  • A common missed cause is water intrusion into the connector behind the wheel well, which creates a resistive path to voltage and mimics a failed sensor; the connector looks fine until you pull the boot back.
  • Aftermarket alarm or remote-start wiring tapped into the wheel speed circuit can back-feed voltage and set this code, so always ask about recent electrical add-ons before condemning the sensor.
  • The code can be intermittent and only set during certain driving conditions such as hard cornering or rough roads, so a static test at the shop may pass; a scan tool with data logging during a road test is more reliable.
  • A weak or corroded ground at the ABS/ESC module can cause a reference voltage shift that reads as a high signal on the sensor circuit, so ground integrity should be verified before replacing any parts.

Can I keep driving with P1398?

You can usually drive the vehicle with this code because normal hydraulic braking remains, but ABS and stability control are disabled, so avoid hard braking, sharp evasive maneuvers, and slippery road conditions until the fault is repaired. If the brake pedal feels abnormal or the warning light is accompanied by a red brake warning, stop driving and have the vehicle towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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