Exhaust Heat Recirculation System Circuit

2AZ-FXE COOLING: EXHAUST HEAT RECIRCULATION SYSTEM: Exhaust Heat Recirculation System Circuit
- Exhaust Heat Recirculation System Circuit

DESCRIPTION

In the exhaust heat recirculation system, coolant is warmed up using conventionally wasted exhaust gas heat to accelerate engine warm-up time, enhancing fuel efficiency and heater performance. Since this system allows the engine to be warmed up with greater efficiency, contributing to low fuel consumption.

The heat recirculator is positioned in the exhaust center pipe assembly after the catalyst. Coolant from the engine flows around the heat recirculator and then returns to the engine. If the engine is started while the engine is cold, the exhaust pipe gas control actuator rod is contracted and the exhaust flow control valve is closed, routing the exhaust gas around the heat recirculator to warm up the coolant.

After the engine coolant temperature rises and the engine has warmed up, the heat of the coolant expands the thermostat and the exhaust pipe gas control actuator rod extends. This opens the exhaust flow control valve to switch to the normal exhaust gas path.

The exhaust flow control valve can also be opened by exhaust gas pressure to prevent insufficient acceleration performance when the engine is cold. In addition, to monitor the engine coolant temperature, a water temperature switch is provided between the engine and the heat recirculator. When the engine coolant temperature is normal, the water temperature switch is closed (on). If the engine coolant temperature is excessively high (overheating), the switch opens (turns off) and the water temperature indicator light in the combination meter assembly illuminate to inform the driver of the malfunction and DTC B1503 is stored B1503.





WIRING DIAGRAM

Refer to System Diagram Description and Operation.

INSPECTION PROCEDURE

PROCEDURE

1. CHECK HARNESS AND CONNECTOR (TEMPERATURE SWITCH - COMBINATION METER - BODY GROUND)

(a) Disconnect the temperature switch connector.

(b) Disconnect the combination meter assembly connector.

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance (Check for Open):





Standard Resistance (Check for Short):





(d) Reconnect the combination meter assembly connector.

(e) Reconnect the temperature switch connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

2. CHECK COMBINATION METER ASSEMBLY

(a) Turn the power switch on (IG).

(b) Disconnect the temperature switch connector.

(c) Check the water temperature indicator light in the combination meter assembly.

Result:





(d) Reconnect the temperature switch connector.

B -- REPLACE WATER TEMPERATURE SWITCH

C -- REPLACE COMBINATION METER ASSEMBLY Removal

A -- SYSTEM OK

3. REPLACE WATER TEMPERATURE SWITCH

(a) Replace the water temperature switch Removal.

NEXT -- Continue to next step.

4. CHECK COMBINATION METER ASSEMBLY

(a) Turn the power switch on (IG).

(b) Disconnect the temperature switch connector.

(c) Check the water temperature indicator light in the combination meter assembly.

Result:





(d) Reconnect the temperature switch connector.

B -- REPLACE COMBINATION METER ASSEMBLY Removal

A -- END