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DTC B1156: Power supply voltage low
 
 
cautionWhen replacing the ECU, always check that the communication circuit is normal.
 
 
DIAGNOSTIC FUNCTION
If the system detects that +B voltage decreases, the KOS&OSS-ECU will set DTC B1156.
 
 
DTC SET CONDITION
Check Conditions
  • The power supply mode is NOT at ON without cranking with the KOS&OSS-ECU activated
Judgment Criterion
  • +B voltage remains 9.0 V or less for at least five seconds.
 
 
PROBABLE CAUSES
  • Damaged wiring harness or connector (+B line short to ground or open circuit)
  • Malfunction of KOS&OSS-ECU
  • Deteriorated battery
 
 
DIAGNOSIS
notePrior to diagnosis, check the battery. (Refer to GROUP 54A, Battery Test .)
STEP 1. Voltage measurement at +B connector (+B line)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Measure the voltage between the +B connector (+B line) and the body ground.
OK: System voltage
Is the check result normal?
Go to Step 3.
Go to Step 2.
 
STEP 2. Check of short to ground or open circuit in +B line between the KOS&OSS-ECU connector and the battery
Is the check result normal?
Go to Step 3.
Repair the connector(s) or wiring harness.
 
STEP 3. Recheck for diagnostic trouble code.
Check again if the DTC is set in the KOS&OSS-ECU.
(1) Erase the DTC.
(2) Turn the power supply mode of the engine switch from "OFF" to "ON".
(3) Check if DTC is set.
(4) Turn the power supply mode of the engine switch from "ON" to "OFF".
Is the DTC set?
Replace the KOS&OSS-ECU and register the VIN (Refer to ).
Intermittent malfunction is suspected (Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).