Inspection Procedure 31
INSPECTION PROCEDURE 31A/C system
A/C Circuit
WIRING DIAGRAM and CONNECTOR VIEW
CIRCUIT OPERATION
- When the A/C is "ON," the battery positive voltage is applied on the ECM (terminal 45) from the Automatic Compressor ECU. When the battery positive voltage is applied on the ECM, the ECM turns "ON" the power transistor in the ECM. The ECM delays A/C engagement momentarily white it creases idle rpm. Then the A/C compressor clutch relay coil will be energized.
With this, the A/C compressor clutch relay turns "ON," and the A/C compressor clutch functions.
TROUBLESHOOTING HINTS
The most likely causes for this case:
- Malfunction of the A/C control system.
- Malfunction of the A/C switch.
- Improper connector contact, open circuit or short-circuited harness wire.
- Malfunction of the ECM.
DIAGNOSIS
STEP 1. Check the circuit at the ECM connector C-51, C-53.
(1) Disconnect connectors C-51 and C-53 and measure at the harness side.
(2) Turn the ignition switch "ON."
(3) Turn the A/C switch "ON."
(4) Measure the voltage between terminals 22, 45 and ground.
- Voltage should be from 0 to 1 volt when the A/C switch is "OFF".
Voltage should be approximately 12 volts (battery positive voltage) when the A/C switch is "ON."
(5) Using a jumper wire, connect terminal 22 to the ground.
- A/C compressor clutch should turn "ON."
(6) Turn the A/C switch "OFF."
(7) Turn the ignition switch "OFF."
If the checks above do not meet the specifications, go to Step 2.
If the checks above meet the specifications, go to Step 3.
STEP 2. Check the harness wire between the ECM connector C-51 and the A/C compressor clutch relay connector A-55X.
NOTE: After inspecting the intermediate connector A-17, inspect the wire. If the intermediate connector A-17 is damaged, repair or replace it. Refer to Harness Connector Inspection. Then confirm that the malfunction symptom is eliminated.
If the wire between the ECM connector C-51 and the A/C compressor clutch relay connector A-55X is damaged, repair it.
If the wire between the ECM connector C-51 and the A/C compressor clutch relay connector A-55X is not damaged, check the A/C system. Then confirm that the malfunction symptom is eliminated.
STEP 3. Check the harness connectors C-51, C-53 at the ECM for damage.
If harness connectors C-51, C-53 are damaged, repair or replace it. Refer to Harness Connector Inspection.
If harness connectors C-51, C-53 are in good condition, replace the ECM.
Then confirm that the malfunction symptom is eliminated.