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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 +B1 voltage decreases, the KOS&OSS-ECU will set DTC B1156.
 
 
JUDGMENT CRITERIA
Check Conditions
  • While the KOS&OSS-ECU is waking up and is not cranking.
Judgment Criterion
  • +B voltage remains 9.0 volts 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 - Battery Test ).
STEP 1. Voltage measurement at +B1 connector (+B1 line)
(1) Disconnect the connector, and measure at the wiring harness side.
(2) Turn the power supply mode of the engine switch from "ON" to "OFF."
(3) Measure the voltage between the +B connector (+B1 line) and the body ground.
OK: The voltage should measure approximately 12 volts (battery positive 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 +B1 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. Check whether the DTC is set again.
Is the DTC set?
Replace the KOS&OSS-ECU and register the ID code (Refer to ).
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).