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Home >> Toyota >> 1998 >> Avalon XLS >> Repair and Diagnosis (Single Page) >> Brakes >> Anti-Lock Brakes >> Anti-Lock Brake System W/O Traction Control >> Diagnostic Tests >> DTC 31, 32, 33, 34, 35, 36, 38 & 39: Speed Sensor Circuit >> Diagnostic Procedure

Diagnostic Procedure

  1. For front speed sensor access, remove fender shield. Disconnect speed sensor connector. Measure resistance between speed sensor connector terminals. Resistance should be 0.6-2.5 k/ohms. Measure resistance between ground and each speed sensor connector terminal. Resistance should be one megohm or more. If resistance is as specified, go to next step. If resistance is not as specified, replace speed sensor.
  2. For rear speed sensor access, remove rear seat cushion and side seat back. Disconnect speed sensor connector. Measure resistance between speed sensor connector terminals. Resistance should be 1.2-2.3 k/ohms. Measure resistance between ground and each speed sensor connector terminal. Resistance should be one megohm or more. If resistance is as specified, go to next step. If resistance is not as specified, replace speed sensor.
  3. Check for open or short circuit in wiring harness between each speed sensor and ABS ECU. See WIRING DIAGRAMS . Repair as necessary. If wiring harness is okay, go to next step.
  4. Check speed sensor installation. Ensure retaining bolt is tightened to specification. See TORQUE SPECIFICATIONS . Ensure zero clearance exists between sensor and front steering knuckle or rear axle carrier. Replace speed sensor if necessary. If speed sensor installation is okay, check speed sensor signal. See SPEED SENSOR DIAGNOSTICS under DIAGNOSIS & TESTING . If speed sensor DTC is present, repair appropriate speed sensor. If signal is normal (light blinks 2 times per second), go to next step.
  5. If oscilloscope is available, check speed sensor signal wave form. Disconnect ABS ECU connector. Connect oscilloscope between terminal GND and terminals FR+, FL+, RR+ and RL+ at ABS ECU connector. See Figure. Drive vehicle at 19 MPH and observe signal wave form. Signal should be smooth and consistent without any irregular wave forms. If wave form is smooth and consistent, replace ABS ECU. If wave form is not smooth and consistent, go to next step.
  6. Check speed sensor rotor for missing teeth or damage. Check sensor tip for scratches, damage or foreign objects. Replace components as necessary. If rotor and sensor are okay, replace ABS ECU.
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