CODE 35, IAC IDLE SPEED ERROR, USING TECH I
Code 35 will set when closed throttle engine speed is 150 RPM greater or less than correct idle speed for 20 seconds.
Note. Test numbers refer to numbers on diagnostic chart.
- Tech 1 RPM control mode is used to extend and retract IAC valve. Movement is verified by an engine speed change. If no change in speed occurs, valve can be retested when removed from throttle body. If IAC valve is retracted beyond control range (about 1500 RPM), many flashes in extend position may occur before engine speed begins to drop. This is normal on certain engines. Fully extending IAC may cause engine to stall. This may be normal.
- This test uses Tech 1 to command IAC-controlled idle speed. Control module issues commands to obtain requested idle speed. Each light on node light should flash red and green while IAC valve is cycled. While sequence of color is not important, check circuits for faults beginning with poor terminal contacts if either light is off or does not flash red and green.
A slow, unstable idle may be caused by a system problem which cannot be overcome by IAC. "Scan" counts will be greater than 60 if idle is too low and zero counts if idle is too high. If idle is too high, stop engine. Fully extend IAC with driver. Start engine. If idle speed is greater than 800 RPM, look for possible vacuum leaks.
If air/fuel ratio is too lean, idle speed may be either too high (check for vacuum leaks) or too low. Engine speed may vary up and down; disconnecting IAC may not help. "Scan" and/or digital voltmeter (10-megohm) will read an oxygen (O2) sensor output less than 300 mv (.3 volt). Check for low fuel pressure or water in fuel. A contaminated O2 sensor (caused by silicone) will produce lean air/fuel mixtures with an O2 sensor output fixed greater than 800 mv (.8 volt). This may also set Code 45.
If air/fuel ratio is too rich, idle speed will be too low and "Scan" tester counts will usually be greater than 80. System may be obviously rich, with black smoke from exhaust pipe. "Scan" tester and/or voltmeter will read an O2 sensor voltage signal fixed greater than 800 mv (.8 volt). Look for high fuel pressure and injectors leaking or sticking. Remove IAC, and inspect bore for foreign material and evidence of IAC valve dragging bore.
Remove IAC, and inspect bore for evidence of IAC valve dragging.
Inspect carefully for loose or corroded connections.
An incorrect PCV valve may cause incorrect idle speed.
