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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
  • Engine starting sequence was completed.
  • Battery positive voltage is higher than 10 volts.
Judgment Criterion
  • Battery backup line voltage is less 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 circuit, harness damage or connector damage.
  • ECM failed.

 
 
DIAGNOSIS
STEP 1. Test the OBD-II drive cycle.
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position 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 the ignition switch to the "ON" position and delete the DTC.
(3) Carry out the test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 1 .
(4) Check the diagnostic trouble code (DTC).
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 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 battery positive voltage.
Is battery positive voltage (approximately 12 volts) present?
Go to Step 3.
Repair or replace the connector(s), or check and repair the harness of short to ground and open circuit in BACK line between battery and ECM connector. Then go to Step 5.
 
STEP 3. Check of harness damage in BACK line between the battery and ECM connector.
Is the harness wire in good condition?
Go to Step 4.
Repair it. Then go to Step 5.
 
STEP 4. Check the trouble symptoms.
(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?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 5.
The inspection is complete.
 
STEP 5. 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.