P1603

Battery Backup Circuit:

Connectors:

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 l,!ne, or loose connector.
- ECM failed.
- PCM failed.

DIAGNOSIS

Required Special Tool:
- 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 DTC P1603 set?

YES: Go to Step 2.
NO: The inspection is complete.

Connectors:

STEP 2. Measure the backup power supply voltage at ECM connector C-120 or PCM connector C-114 by backprobing.

1. Do not disconnect the ECM connector C-120 or PCM connector C-114 .
2. Measure the voltage between terminal No.80 or No. 66 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.

Connectors:

STEP 3. Measure the backup power supply voltage at ECM harness side connector C-120 or PCM harness side connector C-114 .

1. Disconnect the ECM connector C-120 or PCM connector C-114 and measure at the harness side.
2. Measure the voltage between terminal No.80 or No. 66 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 C-06 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 relay box (fuse 24) and ECM connector C-120 (terminal No.80) or PCM connector C-114 (terminal No.66) because of open circuit or short circuit to ground. Then go to Step 6.

Connectors:

STEP 4. Check connector C-120 at ECM or connector C-114 at PCM for damage.

Q: Is the harness connector in good condition?

YES: Check connector C-06 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 relay box (fuse 24) and ECM connector C-120 (terminal No.80) or PCM connector C-114 (terminal No.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.

Connectors:

STEP 5. Check connector C-120 at ECM or connector C-114 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 DTC P1603 set?

YES: Retry the troubleshooting.
NO: The inspection is complete.