Chart A-2, Code 21 - Main Valve
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- ABS Main Valve is an internal solenoid valve in the hydraulic unit. Controlled by the EBCM, it modulates hydraulic pressure to front brakes. Power is supplied from EBCM pin No. 18 through circuit 856. Valve grounds through circuit 155.
- Any abnormal electrical condition in Main Valve circuit will cause Code 21 to set. Anti-lock function will be disabled and "ANTI-LOCK" lamp will turn on.
- Conditions that will cause Code 21 to set include: Short or open main valve solenoid, circuit 856 shorted or open, open in circuit No. 155SH or open in circuit No. 155 between valve block and EBCM (disconnecting ABS valve block will cause Code 21 to set).