LaCrosse FWD L4-2.4L (2011)
Idle Speed: Testing and Inspection
Throttle/Idle Learn
Description
The engine control module (ECM) learns the airflow through the throttle body to ensure the correct idle. The learned airflow values are stored within the
ECM. These values are learned to adjust for production variation and will continuously learn during the life of the vehicle to compensate for reduced
airflow due to throttle body coking. Anytime the throttle body airflow rate changes, for example due to cleaning or replacing, the values must be
relearned.
An engine that had a heavily coked throttle body that has been cleaned or replaced may take several drive cycles to learn out the coking. To accelerate
the process, the scan tool has the ability to reset all learned values back to zero. A new ECM will also have values set to zero.
The idle may be unstable or a DTC may set if the learned values do not match the actual airflow.
Conditions for Running the Idle Learn Procedure
With Scan Tool - Reset Procedure
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DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P0171, P0172, P0201,
P0202, P0203, P0204, P0222, P0223, P0300, P0351, P0352, P0353, P0354, P0496, P0601, P0604, P0606, P0641, P0651, P0697, P06A3, P1516,
P2101, P2119, P2122, P2123, P2127, P2128, P2135, P2138, or P2176 are not set.
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Ignition ON, engine OFF.
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The vehicle speed sensor (VSS) is 0 km/h (0 mph).
Without Scan Tool - Learn Procedure
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DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P0171, P0172, P0201,
P0202, P0203, P0204, P0222, P0223, P0300, P0351, P0352, P0353, P0354, P0496, P0601, P0604, P0606, P0641, P0651, P0697, P06A3, P1516,
P2101, P2119, P2122, P2123, P2127, P2128, P2135, P2138, or P2176 are not set.
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The engine speed is between 450-4,000 RPM.
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The engine vacuum is greater than 5 kPa.
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The mass air flow (MAF) is greater than 2 g/s.
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The ignition 1 voltage is greater than 10 volts.
Idle Learn Procedure
With Scan Tool - Reset Procedure
1. Ignition ON, engine OFF, with a scan tool, perform the Idle Learn Reset in Module Setup.
2. Start the engine, monitor the TB Idle Airflow Compensation parameter. The TB Idle Airflow Compensation value should equal 0 percent and the
engine should be idling at a normal idle speed.
3. Clear the DTCs with a scan tool.
Without Scan Tool - Learn Procedure
Note: Do NOT perform this procedure if DTCs are set. Refer to Diagnostic Trouble Code (DTC) List - Vehicle (See: Powertrain
Management/Computers and Control Systems/Testing and Inspection/Diagnostic Trouble Code Descriptions/Diagnostic Trouble Code (DTC) List
- Vehicle) for further diagnosis.
1. Start and idle the engine in park/neutral for 3 minutes.
2. With a scan tool, monitor the desired and the actual engine speed.
3. The ECM will start to learn the new idle cells and the desired engine speed should start to decrease.
4. Ignition OFF for 60 seconds.
5. Start and idle the engine in park/neutral for 3 minutes.
6. After the 3 minute run time the engine should be idling normal.
Note: During the drive cycle the malfunction indicator lamp (MIL) may illuminate and idle speed DTCs set. If idle speed DTCs set, clear the
DTCs so the ECM can continue to learn.
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If the vehicle is driven for more than 10 km (6 mi) a BARO update is necessary so the ECM can continue to learn. To update the BARO,
accelerate to wide open throttle (WOT) and then release the throttle.
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If the engine idle speed has not been learned the vehicle will need to be driven at speeds above 70 km/h (44 mph) with several decelerations
and extended idles.
7. After the drive cycle, the engine should be idling normally.
