Test Description

The following list gives a description for appropriate step numbers in diagnostic procedure.

1. 1
   
   The DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS, prompts technician to complete some basic checks and store "Freeze Frame" data on scan tool if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 4
   
   This step tests whether PCM can operate IAC valve with scan tool. IAC valve can be commanded to increase and/or decrease engine speed by using scan tool RPM Control function. RPM Control function of scan tool is disabled when any DTCs are set, and when engine is less than normal operating temperature of 176°F (80°C).
3. 5
   
   This step checks operation of Electrical Load idle-up circuits. If there is no increase in IAC Duty Cycle percentage when accessory is turned on, Idle-Up circuit may be inoperative or always ON.
4. 6
   
   This step checks operation of A/C idle-up circuits. If there is no increase in IAC Duty Cycle percentage when A/C compressor is engaged, Idle-Up circuit may be inoperative or always ON.
5. 10
   
   This step checks electrical circuits between IAC valve and PCM.
6. 11
   
   This step determines whether PCM is attempting to control IAC valve. Each IAC Coil Control circuit should indicate a high voltage of 12 volts or more, and then a low voltage of zero to one volt as PCM commands changes in engine speed. Clear all DTCs and operate engine until engine reaches a normal operating temperature before attempting RPM Control with scan tool.