Circuit Description
The Powertrain Control Module (PCM) controls the air entering into the engine with an idle air control (IAC) valve. To increase the idle RPM, the PCM commands the pintle inside of the IAC valve away from the throttle body seat. This allows more air to bypass through the throttle blade. To decrease the RPM, the PCM commands the pintle towards the throttle body seat. This reduces the amount of air bypassing the throttle blade. A scan tool will read the IAC valve pintle position in counts. The higher the counts, the greater the airflow that bypasses the throttle blade.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0201. P0202, P0203, P0204, P0335, P0341, P0342, P0440, P0442, P0446, P0480, P0502, P0503, P0601, P0602, P1133, and P1441 are not set |
| • | The BARO is more than 72 kPa. |
| • | The engine coolant temperature (ECT) is more than 40°C (104°F). |
| • | The engine has been running more than 20 seconds. |
| • | The throttle position (TP) angle is less than 1 percent. |
Conditions for Setting the DTC
| • | The engine RPM is less than the desired RPM by more than 100 RPM for 19 seconds, for a manual transmission. |
| • | The engine RPM is less than the desired RPM by more than 60 RPM for 13 seconds, for an automatic transmission. |
| • | IAC command is more than 145 counts. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the malfunction present. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers. |
| • | A history DTC stores. |
| • | The coolant fan turns ON. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | Use the scan tool to clear the DTCs. |
Diagnostic Aids
| • | Inspect the IAC valve electrical connection for proper mating. |
| • | Inspect the wiring harness for damage. |
| • | Inspect the throttle stop screw for signs of tampering. |
| • | Inspect the throttle linkage for signs of binding or excessive wear. |
| • | A slow or unstable idle may be caused by one of the following conditions: |
| - | The fuel system is too rich or too lean. |
| - | There is foreign material in the throttle body bore or in the air induction system. |
| - | There is a leak or a restriction in the intake manifold. |
| - | There is excessive engine overloading. Check for seized pulleys, pumps, or motors on the accessory drive. |
| - | Overweight engine is being used. |
| • | Refer to Rough, Unstable, or Incorrect Idle and Stalling 2.2L. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Powertrain On-Board Diagnostic (OBD) System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool, if applicable. This creates an electronic copy of the data that was captured when the malfunction occurred. The scan tool stores this data for later reference.
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A normally operating IAC system will be able to be extended and retracted by a scan tool and change the engine idle RPM. The valve movement is verified by an engine RPM change.
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If the scan tool was able to command the IAC valve smoothly, a malfunction may still exist internally within the IAC valve. You can check this by checking the internal resistance of the IAC valve.
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The IAC circuits always have pairs of ground or voltage signals. If the test lamp illuminates on more or less than two terminals, one of the circuits is shorted to voltage or open.
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The IAC circuits always have ground or voltage signals on them in pairs. If the test lamp illuminates on more or less than two terminals, one of the circuits is shorted to ground or open.
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The IAC circuits are constantly switched between ground and voltage. The test lamp should blink on all circuits when it is connected to a ground.
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A test lamp that remains ON constantly indicates that the circuit is shorted to the voltage.
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Thoroughly inspect any suspected circuitry for the following conditions:
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Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline™ information for PCM programming.
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If no malfunctions have been present at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.
| • | Backed-out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Faulty terminal-to-wire connections |
| • | Physical damage to the wiring harness |
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||||
Does the engine RPM change smoothly when the engine is commanded by the scan tool? | 900-2,000 RPM | |||||||||
Are the resistances across terminals A and B and terminals C and D within the specified value? | 40-80 ohms | |||||||||
4 |
Are the resistances across terminals B and C and terminals A and D infinite? | -- | ||||||||
Does the test lamp illuminate on 2 terminals? | -- | |||||||||
Does the test lamp illuminate on 2 terminals? | -- | |||||||||
Does the test lamp flash ON and OFF for all terminals? | -- | |||||||||
Did the test lamp remain ON constantly for the terminals that did not blink? | -- | |||||||||
9 |
Was a repair necessary? | -- | ||||||||
10 |
Was a repair necessary? | -- | ||||||||
Was a repair necessary? | -- | |||||||||
12 |
Was a problem found? | -- | ||||||||
13 |
Was a repair necessary? | -- | ||||||||
14 | Replace the IAC valve. Refer to Idle Air Control Valve Replacement . Is the action complete? | -- | -- | |||||||
|
Important: Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | -- | ||||||||
16 |
Does the scan tool indicate that this diagnostic has run and passed? | -- | ||||||||
Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
