Subaru Forester 2004 Service Manual page 103

Diagnostics Procedure with Diagnostic Trouble Code (DTC)
ABS (DIAGNOSTIC)
F: DTC 27 OPEN OR SHORT CIRCUIT IN REAR LEFT ABS SENSOR CIRCUIT
DIAGNOSIS:
• Faulty ABS wheel speed sensor (Broken wire, input voltage too high)
• Faulty harness connector
TROUBLE SYMPTOM:
ABS does not operate.
ABS-102