P1603

DTC P1603: Battery Backup Circuit Malfunction










TECHNICAL DESCRIPTION

- The ECM 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






Check Conditions

- Engine starting sequence was completed.
- Battery positive voltage is higher than 10 volts.
Judgement Criterion

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

FAIL-SAFE AND BACKUP FUNCTION

- All diagnosis codes are stored once failure judgment is completed.

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
- MB991910: Main Harness A
- MB992110: Power Plant ECU Check Harness

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 It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

STEP 2. Check harness connector B-10 at ECM for damage.

Q. Is the harness connector in good condition?

YES Go to Step 3.
NO Repair or replace it. Harness Connector Inspection.
Then go to Step 5.
STEP 3. Measure the backup power supply voltage at ECM connector B-10 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 No. 104 and ground.

- Voltage should be battery positive voltage.

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

YES Replace the ECM (Refer to, Removal and Installation Removal and Replacement).
Then go to Step 5.

NO Go to Step 4.

STEP 4. Measure the backup power supply voltage at ECM harness side connector B-10.

(1)Disconnect the ECM connector B-10 and measure at the harness side.





(2)Measure the voltage between terminal No. 104 and ground.

- Voltage should be battery positive voltage.

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

YES Repair harness wire between battery and ECM connector B-10 (terminal No. 104) because of harness damage. Then go to Step 5.

NO Repair harness wire between battery and ECM connector B-10 (terminal No. 104) because of open circuit or short circuit to ground. Then go to Step 5.

STEP 5. Using scan tool MB991958, read the diagnostic trouble code
(DTC).

(1)Turn the ignition switch to the "ON" position.

(2)Read the DTC.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC P1603 set?

YES Retry the troubleshooting.
NO The inspection is complete.