Inspection Procedure 26

A/C Switch 2 Signal:

CIRCUIT OPERATION
- The PCM increases the engine idle speed by driving the IAC motor when the automatic compressor-ECU sends a 'A/C ON' signal to the PCM.
- 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 A/C switch 2 signal." The PCM receives this A/C switch 2 signal from the automatic compressor-ECU through terminal 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.
- PCM failed.

DIAGNOSIS




STEP 1. Check the circuit at PCM connector C-90.
1. Disconnect connector C-90, and measure at the harness side.
2. Turn the ignition switch "ON".
3. Turn the A/C switch "ON".
4. Measure voltage between terminal 61 and ground.

- If atmospheric air temperature is 15° C (59° F) or less, the voltage should be 2 volts or less.
- If atmospheric air temperature is 18° C (65.4° F) or more, the voltage should be approximately 12 volts (battery positive voltage).

5. Turn the A/C switch "OFF".
6. Turn the ignition switch "OFF".

If within specifications, go to Step 2.

If not within specifications, check the harness wire and connector between the PCM and the automatic compressor-ECU, and repair or replace if necessary. Refer to vehicle level Testing and Inspection. If the harness wire and connector are in good condition, check the A/C system. Refer to Diagnosis. Then check that the malfunction is eliminated.




STEP 2. Check harness connector C-90 at the PCM for damage.

If harness connector C-90 is not damaged, replace the PCM.

If harness connector C-90 is damaged, repair or replace it.
Refer to vehicle level Testing and Inspection.

Then check that the malfunction is eliminated.