DTC P1603: Battery Backup Line 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

MONITOR EXECUTION

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.

OBD-II DRIVE CYCLE PATTERN

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?

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. Check harness connector B-109 at ECM for damage.

Q. Is the harness connector in good condition?

	Go to Step 3.

	Repair or replace it. Refer to GROUP 00E, Harness Connector Inspection . Then go to Step 5.

STEP 3. Measure the backup power supply voltage at ECM connector B-109 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?

Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, Diagnosis - ID Code Registration Judgment Table <Vehicles with KOS>

or GROUP 42C, Diagnosis - ID Codes Registration Judgment Table <Vehicles with WCM>

. Then go to Step 5.

Go to Step 4.

STEP 4. Measure the backup power supply voltage at ECM harness side connector B-109.

(1)Disconnect the ECM connector B-109 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?

Repair harness wire between battery and ECM connector B-109 (terminal No. 104) because of harness damage. Then go to Step 5.

Repair harness wire between battery and ECM connector B-109 (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?

	Retry the troubleshooting.

	The inspection is complete.