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DTC P1603: Battery Backup Line Malfunction
 
 
 
 
TECHNICAL DESCRIPTION
  • The ECM checks the open circuit of battery backup line.
noteWhen the system detects an open circuit in the battery backup line, it makes 1 failure judgment of other diagnostic trouble codes (DTCs).
 
 
DESCRIPTIONS OF MONITOR METHODS
  • Battery backup line voltage is under specified value.
 
 
MONITOR EXECUTION
  • Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC set in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
DTC SET CONDITIONS
Logic Flow Chart
 
 
Check Conditions
  • Power supply mode of electric motor switch is ON.
  • 12V starter battery positive voltage is higher than 10 volts.
Judgment Criterion
  • Battery backup line voltage has continued to be lower than 6 volts for 2 seconds.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • All diagnostic trouble codes are set once failure judgment is completed.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Open or shorted battery backup line, harness damage or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tool:
  • MB992110: Power Plant ECU Check Harness
STEP 1. Using scan tool (M.U.T.-IIISE), read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn off the power supply mode of the electric motor switch before connecting or disconnecting scan tool (M.U.T.-IIISE).
(1) Connect scan tool (M.U.T.-IIISE). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) .
(2) Turn on the power supply mode of the electric motor switch.
(3) After the DTC has been deleted, read the DTC again.
(4) Turn off the power supply mode of the electric motor switch.
Is DTC P1603 set?
Go to Step 2.
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
 
STEP 2. Measure the backup power supply voltage at ECM connector by using power plant ECU check harness special tool MB992110.
(1) Disconnect all ECM connectors. Connect the power plant ECU check harness special tool MB992110 between the separated connectors.
(2) Measure the voltage between terminal BACK and ground.
  • Voltage should be 12V starter battery positive voltage.
Is 12V starter battery positive voltage (approximately 12 volts) present?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 4.
Go to Step 3.
 
STEP 3. Measure the backup power supply voltage at ECM harness side connector.
(1) Disconnect the ECM connector and measure at the harness side.
(2) Measure the voltage between terminal BACK and ground.
  • Voltage should be 12V starter battery positive voltage.
Is 12V starter battery positive voltage (approximately 12 volts) present?
Repair or replace the connector(s), or check and repair the harness of damage in BACK line between 12V starter battery and ECM connector. Then go to Step 4.
Repair or replace the connector(s), or check and repair the harness of short to ground and open circuit in BACK line between 12V starter battery and ECM connector. Then go to Step 4.
 
STEP 4. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P1603 set?
Retry the troubleshooting.
The inspection is complete.