P1603

DTC P1603: Battery Backup Line Malfunction

Battery Backup Circuit:

TECHNICAL DESCRIPTION
- The ECM is checks the open circuit of battery backup line.

NOTE: When 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 stored 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:

Logic Flow Chart

Check Conditions
- Starting sequence was completed.
- Battery positive voltage is higher than 10 volts.

Judgment Criterion
- Battery backup line voltage has continued to be 6 volts or lower for 2 seconds.

OBD-II DRIVE CYCLE PATTERN
None.

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 Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B

STEP 1. Using scan tool MB991958, read the diagnostic trouble code (DTC).

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.




1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Erase the DTC.
4. Start the engine and run it at idle.
5. Read the DTC.
6. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is DTC P1603 set?

YES: Go to Step 2.

NO: The inspection is complete.

STEP 2. Measure the backup power supply voltage at ECM connector C-119 by backprobing.




1. Do not disconnect the ECM connector C-119.




2. Measure the voltage between terminal No.60 and ground by backprobing.
- Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) present?

YES: Go to Step 5.

NO: Go to Step 3.

STEP 3. Measure the backup power supply voltage at ECM harness side connector C-119.




1. Disconnect the ECM connector C-119 and measure at the harness side.




2. Measure the voltage between terminal No.60 and ground.
- Voltage should be battery positive voltage.

Q: Is battery positive voltage (approximately 12 volts) present?

YES: Go to Step 4.

NO: Check connector A-13 at intermediate connector for damage, and repair or replace as required. If intermediate connector are in good condition, repair harness wire between relay box (fuse 8) and ECM connector C-119 (terminal No.60) because of open circuit or short circuit to ground. Then go to Step 6.




STEP 4. Check harness connector C-119 at ECM for damage.

Q: Is the harness connector in good condition?

YES: Check connector A-13 at intermediate connector for damage, and repair or replace as required. If intermediate connector are in good condition, repair harness wire between relay box (fuse 8) and ECM connector C-119 (terminal No.60) because of harness damage. Then go to Step 6.

NO: Repair or replace it. Then go to Step 6.




STEP 5. Check harness connector C-119 at ECM for damage.

Q: Is the harness connector in good condition?

YES: Replace the ECM. Then go to Step 6.

NO: Repair or replace it. Then go to Step 6.

STEP 6. Using scan tool MB991958, read the diagnostic trouble code (DTC).

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.




1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Read the DTC.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is DTC P1603 set?

YES: Retry the troubleshooting.

NO: The inspection is complete.