DTC 35

Code 35 Chart:

Code 35 Wiring Diagram:

CIRCUIT DESCRIPTION:

The ECM controls idle speed to a calculated, "desired" rpm based on sensor inputs and actual engine rpm, determined by the time between successive 2X ignition reference pulses from the ignition module. The ECM uses 4 circuits to move an idle air control valve (IAC), which allows varying amounts of air flow into the the intake manifold, controlling idle speed.

Code 35 will set when:

^ Engine speed is at least 175 rpm more or less than "desired."
^ TPS voltage indicates throttle is open less than 1%.
^ VSS indicates vehicle speed is less than 3 mph.
^ All above conditions are continuously met for 5 or more.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. The IAC tester is used to extend and retract the IAC valve. Valve movement is verified by an engine speed change If no change in engine speed occurs, the valve can be retested when removed from the throttle body.


2. This step checks the quality of the IAC movement in step 1. Between 700 rpm and about 1500 rpm, the engine speed should change smoothly with each flash of the tester light in both extend and retract. If the IAC valve is retracted beyond the control range (about 1500 rpm), it may take many flashes in the extend position before the engine speed will begin to drop. This is normal on certain engines, fully extending IAC may cause engine stall. This may be normal. Steps 1 and 2 verify proper IAC valve operation while this step checks IAC circuits. Each lamp on the node lights should flash red and green while the IAC valve is cycled. While the sequence of color is not important if either light is "OFF" or does not flash red and green, check the circuits for faults begining with poor terminal contacts.


NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

DIAGNOSTIC AIDS:

^ Check for vacuum leaks, disconnected lines, brittle hoses, cuts, etc. Examine manifold and throttle body gaskets for proper seal. Check for cracked intake manifold.


^ Check for opens, shorts or poor connections to IAC valve in circuits 441, 442, 443, 444. This will result in improper idle control and may set a Code 35.


^ An IAC valve which is stopped and cannot respond to the ECM, a throttle stop screw which has been tampered with, or a damaged throttle body or linkage could cause Code 35. If no problem is found and Code 35 resets, replace ECM.