- Turn the ignition switch OFF.
- Disconnect the redundant brake SW connector.
- Check for open or short to ground in the redundant brake SW circuit wire.
Is a problem found?
YES – Repair open or short to ground in the redundant brake SW circuit wire. 
NO – Go to step 18.
- Replace the redundant brake SW.
- Connect the ECM connector A.
Is there DTC P1550 being output?
YES – Substitute a known-good ECM and recheck. If symptom/indication goes away, replace the original ECM.
NO – System is OK.
| NOTICE |
The battery power supply short circuit to 5 V power supply damages the ECM.
