Inspection Procedure 1: Power Supply Circuit Check: Diagnosis
Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicles Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
- STEP 1. Using scan tool MB991958, read the combination meter diagnostic trouble code.
Check if DTC is set to the combination meter.
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.- Connect scan tool MB991958. Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III)
- Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
- Check if DTC is set.
- Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
- YES: Troubleshoot the combination meter (Refer to DIAGNOSTIC TROUBLE CODE CHART ).
- NO: Go to Step 2.
- STEP 2. Check combination meter connector C-04 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is combination meter connector C-04 in good condition?
- YES: Go to Step 3.
- NO: Repair the defective connector.
- STEP 3. Check the battery power supply circuit to the combination meter. Measure the voltage at combination meter connector C-04.
- Disconnect the connector, and measure at the wiring harness side.
- Turn the ignition switch to the LOCK (OFF) position.
- Measure the voltage between terminals 1 and ground.
- The voltage should measure approximately 12 volts (battery positive voltage).
Q: Is the measured voltage approximately 12 volts (battery positive voltage)?
- YES: Go to Step 5.
- NO: Go to Step 4.
- The voltage should measure approximately 12 volts (battery positive voltage).
- STEP 4. Check the wiring harness between combination meter connector C-04 (terminal 1) and the fusible link (36).
- Check the power supply line (battery supply) for open circuit and short circuit.NOTE: Also check ETACS-ECU connectors C-307 and C-317 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If ETACS-ECU connectors C-307 and C-317 is damaged, repair or replace the damaged component(s) as described in HARNESS CONNECTOR INSPECTION .
Q: Is the wiring harness between combination meter connector C-04 (terminal 1) and the fusible link (36) in good condition?
- YES: The trouble can be an intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
- NO: Repair the wiring harness.
- Check the power supply line (battery supply) for open circuit and short circuit.
- STEP 5. Check the battery power supply circuit to the combination meter. Measure the voltage at combination meter connector C-04.
- Disconnect the connector, and measure at the wiring harness side.
- Turn the ignition switch to the ON position.
- Measure the voltage between terminals 2 and ground.
- The voltage should measure approximately 12 volts (battery positive voltage).
Q: Is the measured voltage approximately 12 volts (battery positive voltage)?
- YES: Go to Step 8.
- NO: Go to Step 6.
- The voltage should measure approximately 12 volts (battery positive voltage).
- STEP 6. Using scan tool MB991958, check data list.
Check the input signal from the ignition switch (IG1) in the ETACS-ECU.
- Check the ETACS data list.
- Turn the ignition switch to the "LOCK" (OFF) position.
Q: Do the scan tool MB991958 display the item "IG voltage" is normal condition?
- YES: Go to Step 7.
- NO: Troubleshoot the ETACS-ECU. Refer to INSPECTION PROCEDURE 2 "THE IGNITION SWITCH (IG1) SIGNAL IS NOT RECEIVED ."
- STEP 7. Check the wiring harness between combination meter connector C-04 (terminal 2) and the fusible link (34).
- Check the power supply line (battery supply) for open circuit and short circuit.NOTE: Also check ETACS-ECU connectors C-309 and C-317 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If ETACS-ECU connector C-309 or C-317 is damaged, repair or replace the damaged component(s) as described in HARNESS CONNECTOR INSPECTION .
Q: Is the wiring harness between combination meter connector C-04 (terminal 2) and the fusible link (34) in good condition?
- YES: The trouble can be an intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
- NO: Repair the wiring harness.
- Check the power supply line (battery supply) for open circuit and short circuit.
- STEP 8. Check the ground circuit to the combination meter. Test at combination meter connector C-04.
- Disconnect combination meter connector C-04 and measure the resistance available at the wiring harness side of the connector.
- Measure the resistance value between terminal 13 and ground.
- The resistance should be 2 ohms or less.
Q: Is the measured resistance 2 ohms or less?
- YES: Go to Step 10.
- NO: Go to Step 9.
- The resistance should be 2 ohms or less.
- STEP 9. Check the wiring harness between combination meter connector C-04 (terminal 13) and ground.
- Check the ground wire for open circuit.
Q: Is the wiring harness between combination meter connector C-04 (terminal 13) and ground in good condition?
- YES: The trouble can be an intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
- NO: Repair the wiring harness.
- Check the ground wire for open circuit.
- STEP 10. Retest the system.
Check that the combination meter works normally.
Q: Is the check result satisfactory?
- YES: The trouble can be an intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
- NO: Replace the combination meter.