Engine Coolant Temperature Communication Circuit - Air Conditioning System

AIR CONDITIONING: AIR CONDITIONING SYSTEM: 14: Engine Coolant Temperature Communication Circuit

DTC 14 - Engine Coolant Temperature Communication Circuit

DESCRIPTION

This circuit converts the resistance of the engine coolant temperature sensor into a pulse signal and transmits to the A/C amplifier.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK DTC
(a) Check that DTC P0115 is not output.
Result:





B -- GO TO ENGINE CONTROL SYSTEM
A -- Continue to next step.

2. INSPECT ECM (THWO)




(a) Remove the ECM with the connectors still connected.
(b) Turn the ignition switch ON.




(c) Measure the waveform between terminal THWO of the ECM connector and body ground.
OK:
Pulse generation
- The correct waveform is as shown.
- The waveform frequency "A" becomes longer as the engine coolant temperature becomes higher, as shown in the chart.





NG -- REPLACE ECM
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (ECM - AIR CONDITIONING AMPLIFIER)
(a) Check for open and short circuit in the harness and the connector between the ECM and the A/C amplifier Electronic Circuit Inspection Procedure.
Result:





C -- REPAIR OR REPLACE HARNESS OR CONNECTOR
B -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
A -- REPLACE AIR CONDITIONING AMPLIFIER