Code
P1398
CADILLAC
P — Powertrain
Wheel Speed Sensor 2, G-Sensor Circuit High Voltage
AI status
Completed
Completed
100%
Causes
- Short to battery or chassis voltage on sensor circuit (wiring pin shorted to 12V)
- Faulty wheel speed or G‑sensor (internal short or failed electronics)
- Corroded/damaged connector or wiring harness (water ingress, chafing)
- Faulty ABS/ESC control module or internal driver circuit
- Incorrect or swapped sensor (wrong type)
- Damaged tone ring or magnetic interference causing erroneous readings
Symptoms
- ABS, Traction Control or StabiliTrak warning lamp illuminated
- Reduced or disabled ABS/traction/stability functions
- Erratic speedometer or wheel speed readings in live data
- Possible abnormal ABS activation or braking behavior
- Diagnostic trouble code P1398 stored
What to check
- Use a scan tool to read freeze frame and live data for wheel speed/G‑sensor channels and note which sensor is affected
- Perform a visual inspection of sensor 2 wiring, connector and tone ring for damage, corrosion or contamination
- Check for related ABS/traction/stability codes that may point to wiring or module faults
- Backprobe the sensor connector with ignition ON and engine OFF to measure reference voltage and signal
- Measure sensor resistance and compare to manufacturer spec (if available)
- Inspect harness for pinched or chafed wiring where it routes over suspension components or the frame
Signal parameters
- Hall‑effect wheel speed sensor: 0–5 V square wave referenced to vehicle 5 V supply; signal toggles with wheel rotation
- VR (magnetic) wheel speed sensor: AC sine voltage typically up to ~1.0–1.5 VAC at moderate wheel speeds (no DC reference)
- G‑sensor/accelerometer (if applicable): typically a 0.5–4.5 V range with ~2.5 V center at rest (manufacturer dependent)
- High voltage fault threshold (typical): sensor circuit voltage above ~5.5 V is considered out of range (may vary by OEM)
- Open/low thresholds: near 0 V (open or short to ground) or no waveform present
Diagnostic algorithm
- Connect a scan tool, confirm P1398 and record freeze frame/live data for Wheel Speed Sensor 2 and related channels.
- Visually inspect sensor 2, connector and harness for damage, contamination, loose pins, and bent or corroded terminals.
- With ignition ON (engine OFF) backprobe the sensor connector: verify reference supply (usually +5 V for Hall sensors) and ground presence. If reference voltage is above ~5.5 V, suspect short to battery/incorrect supply or module fault.
- Measure sensor resistance (for a VR sensor) and compare to spec. For Hall sensors verify 5 V supply and check the signal line for DC offset at rest.
- Wiggle the harness and connector while monitoring live data; note intermittent changes which indicate wiring/connector faults.
- Spin the wheel (or road test with safe measures) while observing the waveform with an oscilloscope or the scan tool: verify correct waveform shape and amplitude. For Hall sensors expect a square wave; for VR sensors expect AC waveform proportional to speed.
- If wiring or connector fault is found, repair or replace damaged wiring/connector and retest.
- If wiring is good and sensor fails bench/onsite tests, replace the wheel speed/G‑sensor and retest.
- If sensor and wiring check good, suspect ABS/ESC control module driver fault; further module-level diagnostics or replacement may be required.
- Clear codes and perform a road test to confirm the fault does not return.
Likely causes
- Short to battery voltage on Wheel Speed Sensor 2 circuit
- Failed wheel speed/G‑sensor at wheel/hub assembly
- Corroded/loose connector at the sensor harness
Fault status
Status
Wheel Speed Sensor 2 / G‑Sensor Circuit High Voltage — the ABS/ESC module is detecting voltage above the expected range on the sensor 2 input. ABS/traction/stability may be disabled until corrected.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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