Inspection Procedure 27

A/C Switch 2 Signal:

CIRCUIT OPERATION
- The ECM or PCM increases the engine idle speed by driving the IAC motor when the automatic compressor-ECU sends a "AC on" signal to the module.
- The automatic compressor-ECU detects how the air conditioning is applying load to the engine, and converts the information to a voltage signal (High voltage=low load, Low voltage=high load). This voltage signal is called "AC switch 2 signal." The ECM or PCM receives this AC switch 2 signal from the automatic compressor-ECU through terminal 65 or 61 , and determines the idle-up speed according to the high or low air conditioning load.

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Malfunction of the A/C control system.
- Open or shorted circuit, or improper connector contact.
- ECM failed.
- PCM failed.

DIAGNOSIS

STEP 1. Check the voltage at ECM connector C-58 or PCM connector C-55 .
1. Measure the voltage between terminal 65 or 61 and the ground under following condition. (Connectors should not be disconnected.)
a. Engine: Warm, idle
b. Outside temperature: 25°C (77°F) or higher

Standard value:
Battery positive voltage
(A/C temperature control: Maximum cooling position)
0 - 3 volts
(A/C temperature control: Maximum heating position)

If within specifications, go to Step 2.

If not within specifications, check the A/C system. Refer to - Heater, Air Conditioning and Ventilation Diagnosis.

STEP 2. Check harness connector C-58 at the ECM or harness connector C-55 at the PCM for damage.
If harness connector C-58 or C-55 is not damaged, replace the ECM or PCM.

If the harness connector C-58 or C-55 is damaged, repair or replace it. Refer to Harness Connector Inspection.
Then check that the malfunction is eliminated.