Code No.B1156 Power supply voltage low

caution

When 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 diagnosis code No. B1156.

JUDGEMENT CRITERIA

Check Conditions

The power supply mode is NOT at ON without cranking with the KOS&OSS-ECU activated

Judgement 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 earth or open circuit)
Malfunction of KOS&OSS-ECU
Deteriorated battery

DIAGNOSIS PROCEDURE

note

Prior 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 earth.
OK: System voltage

Q. Is the check result normal?

Go to Step 3.

Go to Step 2.

STEP 2. Check of short to earth or open circuit in +B line between the KOS&OSS-ECU connector and the battery

Q. Is the check result normal?

Go to Step 3.

Repair the connector(s) or wiring harness.

STEP 3. Check whether the diagnosis code is set again.

Q. Is the diagnosis code set?

Replace the KOS&OSS-ECU and register the chassis number (Refer to

Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction