Test 2: Wheel Sensor Short Circuit

Ensure wheel sensor bolts and tone wheel bolts are tight. See TORQUE SPECIFICATIONS . Go to next step.
Measure sensor to tone wheel air gap around entire wheel. Ensure gap is within specification. See WHEEL SPEED SENSOR AIR GAP under ADJUSTMENTS. If gap is too small, use Spacer (26755AA000) to increase gap to specification. If gap exceeds specification, remove spacer(s) and replace tone wheel or faulty wheel speed sensor. When gap is set, go to next step.

If an oscilloscope is not available, go to step 5. If an oscilloscope is available, raise and support vehicle with wheels off of ground. Turn ignition off. On Forester and Impreza, connect oscilloscope to appropriate connector terminals at Blue bulkhead connector B100, located at top left corner of dash, and 12-pin wiring harness connector F55, located behind instrument cluster. See Fig 1. See CHECKING ABS SENSOR SIGNAL USING OSCILLOSCOPE (FORESTER & IMPREZA) table. On Legacy, connect oscilloscope to appropriate connector terminals at Blue bulkhead connector B100, located at top left corner of dash, and 8-pin wiring harness connector F1, located at top left corner of dash. See Fig 2. See CHECKING ABS SENSOR SIGNAL USING OSCILLOSCOPE (LEGACY) table.

CHECKING ABS SENSOR SIGNAL USING OSCILLOSCOPE (FORESTER & IMPREZA)

DTC

⁽¹⁾⁽²⁾ Connector (Terminals No.)

B100 (5 & 14)

B100 (7 & 16)

F55 (6 & 7)

F55 (1 & 2)

⁽¹⁾	See Fig 1.

⁽²⁾	Second terminal listed is to be connected to oscilloscope ground lead.

CHECKING ABS SENSOR SIGNAL USING OSCILLOSCOPE (LEGACY)

DTC

⁽¹⁾⁽²⁾ Connector (Terminals No.)

B100 (12 & 13)

B100 (3 & 4)

F1 (5 & 4)

F1 (2 & 1)

⁽¹⁾	See Fig 2.

⁽²⁾	Second terminal listed is to be connected to oscilloscope ground lead.

NOTE: This test procedure, when completed, may set DTC 29.

On all models, turn ignition on. Observe oscilloscope while rotating each wheel, depending on trouble code. Voltage reading on oscilloscope should be .12-1.00 volt (AC waveform). If voltage is not as specified or waveform is erratic, go to next step. If voltage and waveform is as specified, go to step 7.
Check sensor and tone wheel for damage or contamination. Clean, repair or replace as needed. Go to next step.
Check hub runout. If runout is less than .002" (.05 mm), go to next step. If runout is .002" (.05 mm) or more, replace hub.
Turn ignition off. Depending on specific trouble code, disconnect appropriate ABS wheel sensor connector. Measure resistance between wheel sensor terminals. If resistance is 800-1200 ohms (Forester, Impreza rear and Legacy) or 1000-1500 ohms (Impreza front), go to next step. If resistance is not 800-1200 ohms (Forester, Impreza rear and Legacy) or 1000-1500 ohms (Impreza front), replace wheel sensor.
Measure resistance between ground and wheel sensor terminal No. 1. If resistance is more than one megohm, go to next step. If resistance is less than one megohm, replace wheel sensor.

Reconnect wheel sensor connector. Disconnect ABSCM/HU connector. Check resistance of sensor circuit at ABSCM/HU connector terminals. See CHECKING WHEEL SENSOR CIRCUITS (TEST 2) table. See Figure. If resistance is 800-1200 ohms, go to next step. If resistance is not 800-1200 ohms, repair wiring between wheel sensor and ABSCM/HU.

CHECKING WHEEL SENSOR CIRCUITS (TEST 2)

DTC

⁽¹⁾ Terminals No.

11 & 12

9 & 10

26 (Forester)

13 & 15

26 (Impreza & Legacy)

14 & 15

7 & 8

⁽¹⁾	At ABSCM/HU connector. See Figure.

Measure resistance between ground and ABSCM/HU connector terminals as specified. See CHECKING WHEEL SENSOR CIRCUITS FOR SHORT (TEST 2) table. If resistance is more than one megohm, go to next step. If resistance is less than one megohm, repair short in wiring harness between wheel sensor and ABSCM/HU.

CHECKING WHEEL SENSOR CIRCUITS FOR SHORT (TEST 2)

DTC

⁽¹⁾ Terminal No.

26 (Forester)

26 (Impreza & Legacy)

⁽¹⁾	At ABSCM/HU connector. See Figure.

Measure resistance between ground and ABSCM/HU connector terminal No. 23. If resistance is less than .5 ohm, go to next step. If resistance is .5 ohm or more, repair wiring harness between ground and ABSCM/HU.
Check ABSCM/HU connector and wheel sensor connector contacts. If connector contacts are poor, repair contacts. If contacts are okay, go to next step.
Ensure car telephone or wireless transmitter are properly installed and routed away from sensor harness. Go to next step.

Reconnect all connectors. Measure resistance between ground and shield connector terminals at appropriate connector(s). See ABS WHEEL SENSOR SHIELD CONNECTOR TERMINAL IDENTIFICATION (FORESTER & IMPREZA) or ABS WHEEL SENSOR SHIELD CONNECTOR TERMINAL IDENTIFICATION (LEGACY) table. If resistance is less than .5 ohm, go to next step. If resistance is .5 ohm or more, repair shield harness.

ABS WHEEL SENSOR SHIELD CONNECTOR TERMINAL IDENTIFICATION (FORESTER & IMPREZA)

DTC

⁽¹⁾ Connector (Terminal No.)

B100 (15)

B100 (6)

F55 (8)

F55 (3)

⁽¹⁾	For terminal locations, see Figure.

ABS WHEEL SENSOR SHIELD CONNECTOR TERMINAL IDENTIFICATION (LEGACY)

DTC

⁽¹⁾ Connector (Terminal No.)

B100 (11)

B100 (2)

⁽²⁾

⁽¹⁾	For terminal locations, see Figure.

⁽²⁾	Go to step 15.

Reconnect all connectors. Erase memory. Recheck for trouble codes. If same trouble code returns, replace ABSCM/HU. If other trouble codes exist, go to proper test procedure. If no trouble codes exist, problem was a temporary noise interference. Recheck harness and connectors.

Fig 1: Connecting Oscilloscope To Connectors B100 & F55 (Forester & Impreza)

Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Connecting Oscilloscope To Connectors B100 & F1 (Legacy)

Courtesy of SUBARU OF AMERICA, INC.