Test Description

The numbers below refer to the step numbers in the diagnostic procedure.

1. 1
   
   The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 2
   
   This step verifies whether the PCM responds to the operation of the rear defogger. The IAC Motor Command Cycle percentage and the idle speed will increase when the rear defogger is turned ON if the idle-up system is okay.
3. 3
   
   This step verifies whether the PCM responds to the operation of the taillights. The IAC Motor Command Cycle percentage and the idle speed will increase when the taillights are turned ON if the idle-up system is okay.
4. 4
   
   This step verifies the operation of the A/C idle circuit. If the engine idle speed and IAC Motor Command cycle increase when the A/C is turned ON, the A/C idle circuit is functioning normally.
5. 5
   
   This step verifies the operation of the Power Steering Pressure (PSP) switch circuit. If the engine idle speed and IAC Motor Command increase when the steering wheel is turned to 90 percent, the PSP switch idle circuit is functioning normally.
6. 6
   
   This step tests the PSP switch signal circuit for voltage from the PCM.
7. 7
   
   This step tests the operation of the PSP switch.
8. 10
   
   The A/C compressor clutch should not be engaged with the A/C switch Off. The PCM will not increase engine idle speed when the A/C compressor is supposed to be off.
9. 13
   
   If the A/C compressor clutch engages, the compressor clutch, the relay, and the control circuit are all OK. The PCM will then need to be replaced because there was no increase in the IAC motor command percentage during A/C operation in step 4)  .
10. 22
    
    This step tests for a short to ground in the diagnostic request circuit. A short to ground in the diagnostic request circuit can cause the PCM to ignore the idle-up signals to the PCM. A short in the diagnostic request circuit will cause the IAC motor command and the idle speed to remain fixed.