Code 51: Valve Relay Always Off

Remove and test valve relay. See HYDRAULIC UNIT RELAYS under COMPONENT TESTING. Replace relay if faulty. If relay is okay, measure voltage between relay receptacle terminal No. 6 and ground. See Fig 1 . If battery voltage is present, go to step 3).
If battery voltage is not present, check condition of fuse No. 1. Replace fuse as needed. If fuse is okay, inspect and repair circuit between fuse No. 1 and relay receptacle terminal No. 6.
Install valve relay. Ensure ignition is off. Disconnect ABS ECU harness connector. Turn ignition on. Measure voltage between ECU harness connector terminal No. 13 and ground. See Figure . If battery voltage is present, go to step 5).
If battery voltage is not present, turn ignition off. Remove valve relay. Using ohmmeter, check continuity between relay receptacle terminal No. 5 and ECU terminal No. 13. If continuity does not exist, inspect and repair circuit as needed. If continuity exists, inspect and repair circuit between fuse No. 13 and relay receptacle No. 2.
Measure voltage between ECU harness connector terminal No. 43 and ground. If battery voltage is present, replace ABS ECU and retest. If battery voltage is not present, inspect and repair circuit between ECU terminal No. 43 and relay receptacle terminal No. 3. See WIRING DIAGRAM.

Fig 1: Identifying Valve Relay Harness Connector

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA