P1603

Battery Backup Circuit:

Connectors:

TECHNICAL DESCRIPTION
- The ECM or PCM 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).

DTC SET CONDITIONS

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

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

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Open or shorted battery backup line, or loose connector
- ECM failed.
- PCM failed.

NOTE: When the engine is started with the IOD or storage connector disconnected, the ECU or PCM judges that an open circuit has occurred in the battery backup line. Consequently, the service engine soon/malfunction indicator lamp illuminates and the DTC is stored in memory

DIAGNOSIS

Required Special Tools
- MB991502: Scan Tool (MUT-II)

STEP 1. Using scan tool MB991502, read the diagnostic trouble code (DTC).

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502

1. Connect scan tool MB991502 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 the DTC P1603 output?

YES: Go to Step 2.

NO: The inspection is complete.

STEP 2. Check the backup power supply voltage at ECM connector C-115 or PCM connector C-118 by backprobing.
1. Do not disconnect the ECM connector C-115 or PCM connector C-118 .

2. Measure the voltage between terminal 80 or 66 and ground by backprobing.
- Voltage should be battery positive voltage.

Q: Is the voltage normal?

YES: Go to Step 5.

NO: Go to Step 3.

STEP 3. Check the backup power supply voltage at ECM harness side connector C-115 or PCM harness side connector C-118 .
1. Disconnect the ECM connector C-115 or PCM connector C-118 and measure at the harness side.

2. Measure the voltage between terminal 80 or 66 and ground.
- Voltage should be battery positive voltage.

Q: Is the voltage normal?

YES: Go to Step 4.

NO: Check connectors C-05, C-123 and C-129 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector are in good condition, repair harness wire between battery and ECM connector C-115 terminal 80 or PCM connector C-118 terminal 66 because of open circuit or short circuit to ground. Then go to Step 6.

STEP 4. Check connector C-115 at ECM or connector C-118 at PCM for damage.

Q: Is the harness connector in good condition?

YES: Check connectors C-05, C-123 and C-129 at intermediate connector for damage, and repair or replace as required. Refer to Harness Connector Inspection. If intermediate connector are in good condition, repair harness wire between battery and ECM connector C-115 terminal 80 or PCM connector C-118 terminal 66 because of harness damage. Then go to Step 6.

NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 6.

STEP 5. Check connector C-115 at ECM or connector C-118 at PCM for damage.

Q: Is the harness connector in good condition?

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

NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 6.

STEP 6. Using scan tool MB991502, read the diagnostic trouble code (DTC).

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.

1. Connect scan tool MB991502 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 the DTC P1603 output?

YES: Retry the troubleshooting.

NO: The inspection is complete.