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 the IAC valve away from the throttle body seat. This allows more air to bypass the throttle plate. To decrease the RPM, the PCM commands the pintle towards the throttle body seat. This reduces the amount of air bypassing the throttle plate. A scan tool will read the IAC valve pintle position in counts. The higher the counts, the greater the airflow bypassing the throttle plate.
• | The following DTCs are not set: P0105, P0107, P0108, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0201, P0202, P0203, P0204, P0300, P0325, P0335, P0341, P0342, P0440, P0442, P0446, P0452, P0453, P0480, P0481, P0502, P0503, P0601, P0602, P1133, P1441 and P1621. |
• | The barometric pressure (BARO) is more than 72 kPa. |
• | The engine coolant temperature (ECT) is more than 40°C (104°F). |
• | The engine has been running for more than 20 seconds. |
• | The throttle position (TP) angle is less than 1 percent. |
• | The idle speed deviates above the desired RPM by more than 60 RPM for more than 13 seconds. |
• | The IAC valve reads less than 2 counts on the scan tool. |
• | The malfunction indicator Lamp (MIL) will illuminate after 2 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. |
• | The MIL will turn off after 3 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 a scan tool to clear the DTCs. |
• | Inspect the IAC valve electrical connection for proper mating. |
• | Inspect the wiring harness for damage. |
• | Inspect for any disconnected, cracked, or cut vacuum hoses. |
• | Inspect the intake manifold and the throttle body for leaks. |
• | Inspect the intake manifold for cracks. |
• | Refer to Rough, Unstable, or Incorrect Idle and Stalling in Symptoms. |
The numbers below refer to step numbers on the diagnostic table.
Step | Action | Values | Yes | No | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |||||||||||
2 |
Does the RPM change smoothly when commanded? | 700-1500 RPM | Go to Diagnostic Aids | Go to Step 3 | ||||||||||
3 |
Does the node lamp cycle? | -- | Go to Step 5 | Go to Step 4 | ||||||||||
4 |
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 | ||||||||||
5 |
Did you find and correct any of these conditions? | -- | Go to Step 10 | Go to Step 6 | ||||||||||
6 |
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 | ||||||||||
7 | Replace the IAC valve. Refer to Idle Air Control Valve Replacement Did you complete the repair? | -- | Go to Step 10 | -- | ||||||||||
8 |
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 | ||||||||||
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 10 | -- | |||||||||||
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |