Code 35: Idle Speed Control Circuit

Code 35 indicates that the ECM has seen the voltage at ECM term. "8" continually low with the throttle open. This indicates that the circuit through the ISC throttle switch is grounded. The voltage should go to 12 volts when the switch opens. A grounded circuit will cause stalling because the ECM will retract the ISC plunger completely resulting in low idle speed.

1. This step separates a shorted ISC throttle switch from a TPS/MAP/VAC problem. If the "SERVICE ENGINE SOON" light appears at idle on a restart, the fault is in the TPS/MAP/VAC circuits. Due to ECM calibration, a Code 35 could appear before a 21, 32 or 34 with a faulty TPS or faulty MAP/VAC sensor ground circuit.
2. This step checks for an open ground in circuit to ECM or ECM itself. If the test light is "ON", the fault is in the TPS circuit even though the conditions above may have set a Code 35.
3. This test verifies an ISC throttle switch failure. Raising RPM above 1200 takes the throttle off contact with the ISC. It also keeps a Code 21 from being set when TPS is depressed.
4. This step checks for a malfunctioning ISC nose switch with the connector off of the ISC motor. An ohmmeter should read infinite resistance (open circuit) when the throttle is moved off of the nose switch (and virtually zero with it closed).
5. With the harness disconnected, the voltage from term. "B" to "A" should be about 12 volts.

Fig 1: Code 35: Idle Speed Control Circuit Flow Chart