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 the closed throttle engine speed is 300 rpm above or below the desired (commanded) idle speed for 20 seconds.

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.

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

1. Continue with test even if engine will not idle. If idle is too low, "Scan" will display 80 or more counts, or steps. If idle is high it will display "0" counts. Occasionally an erratic or unstable idle may occur. Engine speed may vary 200 rpm or more up and down. Disconnect IAC. If the condition is unchanged, the IAC is not at fault. There is a system problem. Proceed to diagnostic aids below.

2. When the engine was stopped, the IAC Valve retracted (more air) to a fixed "Park" position for increased air flow and idle speed during the next engine start. A "Scan" will display 80 or more counts. Observe idle immediately as on a warm engine, the idle speed should decrease rapidly.

3. Be sure to disconnect the IAC valve prior to this test. The test light will confirm the Electronic Control Module (ECM) signals by a steady or flashing light on all circuits.

4. There is a remote possibility that one of the circuits is shorted to voltage which would have been indicated by a steady light. Disconnect ECM and turn the ignition "ON" and probe terminals to check for this condition.


DIAGNOSTIC AIDS:

^ A slow unstable idle may be caused by a system problem that cannot be controlled by the IAC. "Scan" counts will be above 80 counts if idle is too low and "0" counts if it is too high. If idle is too high, stop engine. Ignition "ON." Ground diagnostic terminal, Wait a few seconds for IAC to seat then disconnect IAC. Start engine. If idle speed is above 550 rpm in drive with an Automatic Transmission/Transaxle (A/T) or 650 in neutral with a Manual Transmission/Transaxle (M/T), locate and correct vacuum leak. If rpm is below specification, check for foreign material around throttle plates and if OK, reset minimum idle speed. See Adjustment procedures.

^ System too lean (High Air/fuel ratio Idle speed may be too high or too low. Engine speed may vary up and down, disconnecting IAC does not help. This may set Code 44. "Scan" and/or Voltmeter will read an oxygen sensor output less than 300 mV (0.3 volt). Check for low regulated fuel pressure or water in fuel. A lean exhaust with an oxygen sensor output fixed above 800 mV (0.8 volt) will be a contaminated sensor, usually silicone. This may also set a code 45 or 61.

^ System too rich (Low Air/fuel ratio) Idle speed too low, "Scan" counts usually above 80. System obviously rich and may exhibit black smoke exhaust. "Scan" tool and/or Voltmeter will read an oxygen sensor signal fixed above 800 mV (0.8 volt).

Check:

^ For fuel in pressure regulator hose
^ High fuel pressure
^ Injector leaking or sticking.
^ Throttle body. Remove IAC and inspect bore for foreign material or evidence of IAC valve dragging the bore.
^ A/C Compressor or Relay failure. See CHART C-10. If the A/C control relay drive circuit is shorted to ground, or if the relay is faulty, an idle problem may exist.
^ If above are all OK, See DIAGNOSIS BY SYMPTOM.