Inspection Procedure 5

INSPECTION PROCEDURE 5: Engine Coolant Temperature Gauge does not Work.

Engine Coolant Temperature Gauge Circuit Part 1:

Engine Coolant Temprature Gauge Circuit Part 2:

CIRCUIT OPERATION
- The ignition switch (IG1) circuit is the power source for the engine coolant temperature gauge.
- Resistance value, which the engine coolant temperature gauge unit sends to the combination meter, is dependent on temperature of the engine coolant. This causes circuit current to fluctuate.
- The engine coolant temperature gauge moves the needle according to the circuit current.

TECHNICAL DESCRIPTION (COMMENT)
The cause is thought to be due to malfunction of engine coolant temperature gauge unit or the combination meter.

TROUBLESHOOTING HINTS
- Malfunction of the engine coolant temperature gauge unit
- Malfunction of the combination meter
- Damaged wiring harness or connectors

DIAGNOSIS

Required Special Tool:
- MB991223: Harness Set

STEP 1. Check with other meter.

Check to see that the speedometer, tachometer and fuel gauge operate normally.

Q: Do all other meters operate?

YES : Go to Step 2.

NO : Refer to INSPECTION PROCEDURE 6.

STEP 2. Check the engine coolant temperature gauge unit.

Check to see that the engine coolant temperature gauge unit operate normally.

Q: Is the engine coolant temperature gauge unit normal?

YES: Go to Step 3.

NO: Replace the engine coolant temperature gauge unit. The engine coolant temperature gauge should work normally.










STEP 3. Check engine coolant temperature gauge unit connector B-112 and combination meter connector C-02 for damage.

Q:Are engine coolant temperature gauge unit connector B-112 and combination meter connector C-02 in good condition?

YES: Go to Step 4.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. The engine coolant temperature gauge should work normally.













STEP 4. Check the wiring harness between engine coolant temperature gauge unit connector B-112 (terminal 1) and combination meter connector C-02 (terminal 50).

NOTE: Also check intermediate connector C-124. If intermediate connector C-124 is damaged, repair or replace the connector as described in Harness Connector Inspection.

Q:Are the wiring harness between engine coolant temperature gauge unit connector B-112 (terminal 1) and combination meter connector C-02 (terminal 50) in good condition?

YES: Repair or replace the combination meter. The engine coolant temperature gauge should work normally.

NO: Repair the wiring harness. The engine coolant temperature gauge should work normally.