Subaru IMPREZA 2002 Service Manual page 239

DIAGNOSTICS CHART WITH DIAGNOSIS CONNECTOR
ABS (DIAGNOSTICS)
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L: DTC29
ABNORMAL ABS SENSOR SIGNAL (ANY ONE OF FOUR)
DIAGNOSIS:
Faulty ABS sensor signal (noise, irregular signal, etc.)
Faulty tone wheel
Wheels turning freely for a long time
TROUBLE SYMPTOM:
ABS does not operate.
ABS-53