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What is a 35 code for 93 chevy pickup 350.

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What is a 35 code for 93 chevy pickup 350.


this is a problem with the idle air control valve


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Powertrain Controls - ECM/PCM


Chart DTC 35 Idle Speed Error
Circuit Idle Speed Error

The Idle Air Control(IAC) motor will constantly adjust its valve position to maintain the desired idle speed If idle speed is below the desired idle, the valve will open to allow more air flow and increase RPM. If the idle is too high, the IAC will slowly close to limit airflow and therefore engine RPM will decrease. If engine RPM becomes out of control for a long enough period, then a Diagnostic Trouble Code (DTC) 35 will be set. Review the description of the IAC valve.

DTC 35 Will Set When: DTC 24 is not present. Power steering is not cramped. Closed throttle engine speed is 350 RPM above or below desired idle for 50 seconds.

Action Taken (PCM will default to): The Powertrain Control Module (PCM) will turn the Malfunction Indicator Lamp (MIL) "ON" and set a DTC 35. The RPM will remain controlling erratically until the problem is corrected.

DTC 35 Will Clear When: A current DTC 35 will clear when the engine speed controls within a 350 RPM range of desired idle. A History DTC 35 will clear after 50 consecutive ignition key cycles without a current DTC 35 being stored.

Number(s) below refer to circled number(s) on the diagnostic chart.


  1. The Tech 1 RPM control mode is used to extend and retract the IAC valve. The valve should move smoothly within the specified range. If the idle speed is commanded (IAC extended) too low (below 700 RPM), the engine may stall. This may be normal and would not indicate a problem. Retracting the IAC beyond its controlled range (above 1500 RPM) will cause a delay before the RPMs start dropping. This too is normal.
  2. This test uses the Tech 1 scan tool to command the IAC controlled idle speed The PCM issues commands to obtain commanded idle speed. The node lights each should flash red and green to indicate a good circuit as the PCM issues commands. 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 beginning with poor terminal contacts.


  • A slow, unstable, or fast idle may be caused by a non-IAC system problem that cannot be overcome by the IAC valve. Out of range IAC counts will be above 60 if idle is too low and zero counts if idle is too high. If idle speedis above 600-700 RPM in drive with an A / T, locate and correct vacuum leak. If RPM is below spec., check for foreign material around throttle plates. The following checks should be made to repair a non-IAC system problem.
  • Vacuum leak high idle. If idle is too high, stop the engine. Fully extend IAC with tester. Start engine. If idle speed is above 800 RPM, locate and correct vacuum leak including crankcase ventilation system. Also check for binding of throttle blade or linkage.
  • System too lean (high air / fuel ratio). The idle speed may be too high or too low. Engine speed may vary up and down and disconnecting the IAC valve does not help. DTC 44 may set. Tech 1 (or equivalent scan tool) Heated Oxygen Sensor (HO2S) voltage will be less than 300 mV (.3 volt). Check for low regulated fuel pressure water in the fuel or a restricted injector.
  • System too rich (low air / fuel ratio). The idle speed will be too low. Tech 1 (or equivalent scan tool) IAC counts will usually be above 80. System is obviously rich and may exhibit black smoke in exhaust. DTC 45 may set. Tech 1 (or equivalent) scan tool HO2S voltage will be fixed above 800 mV (.8 volt). Check for high fuel pressure, leaking or sticking injector. Silicone contaminated HO2S will cause sluggish voltage variations on Tech 1 scan tool.
  • Throttle bodyRemove IAC valve and inspect bore or foreign material.
  • IAC valve electrical connections. IAC valve connections should be carefully checked for proper contact.
  • Crankcase ventilation valve. An incorrect or faulty valve may result in an incorrect idle speed
  • Refer to Diagnosis by Symptom / Rough, Unstable or Incorrect Idle,Stalling . See: Symptom Related Diagnostic Procedures\Rough, Unstable or Incorrect Idle/Stalling
  • If intermittent poor driveability or idle symptoms are resolved by disconnecting the I AC carefully recheck connections, valve terminal resistance, or replace IAC.
  • A/C compressor or relay failure. Refer to Diagnostic Charts / 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. See: Symptom Related Diagnostic Procedures\A - E Charts & Related Test Procedures\C Charts\Chart C-10 A/C Clutch Control Circuit Diagnosi
  • If above are OK, see Diagnosis by Symptom / Rough, Unstable or Incorrect Idle,Stalling . See: Symptom Related Diagnosti
Service and Repair


Fig. 166 Idle Air Control Assembly



  1. Remove air cleaner, then disconnect electrical connection from Idle Air Control (IAC).
  2. Using a suitable wrench, remove IAC assembly from throttle bodyand discard valve gaskets. Before installing new IAC assembly, measure extension of conical valve, Fig. 166. Make measurement from motor housing to end of pintle. The extension should be 11/8 inch. If cone is extended too far, the motor may be damaged during installation.


    Identify replacement IAC assembly as being either Type 1 or Type 2, Fig. 166. If dimension ``A'' is greater than 11/8 inch, reduce distance as follows:
    On Type 1, exert a firm pressure on conical valve to retract it.
    On Type 2, while turning valve in clockwise rotation, compress retaining spring from conical valve. Return spring to original position with straight part of spring end aligned with flat surface of valve.

    1. Install new IAC assembly to throttle body. Torque motor to 13 ft. lbs.
    2. Reconnect IAC electrical connection and install air cleaner.
    3. Start engine and run until normal operating temperature is reached. On 1984-88 vehicles, the ECM will reset idle speedwhen vehicle is driven over 35 mph.
Tim's Auto Repair, mechanic
Category: Chevy
Satisfied Customers: 15301
Experience: Have owned a repair shop for 25 yrs.
Tim's Auto Repair and 5 other Chevy Specialists are ready to help you
Customer: replied 7 years ago.
Thanks, XXXXX XXXXX a vacuum leak


glad you got it

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