Figure 1.1 – Fast Idle Warmup (ISL8.3 CM850)

Feature Description

Fast Idle Warmup increases idle speed and operates the engine on three cylinders during extended idle periods in cold conditions. It activates when:

• The engine idles for 30 seconds.
• No vehicle speed is detected.
• Coolant temperature is at or below 140°F.
• Intake manifold temperature is at or below 15°F.

Once activated, the idle speed increases to 1200 RPM while three cylinders are cut out, and fueling for the active cylinders is increased to improve combustion efficiency and engine temperature.

If coolant temperature is below 32°F, Fast Idle Warmup activates regardless of intake manifold temperature. It automatically deactivates when coolant temperature exceeds 170°F or under these conditions:

• The clutch is depressed (on vehicles with a clutch switch).
• The service brake pedal is depressed.
• The accelerator is pressed.

After deactivation, the engine returns to normal idle on all six cylinders.

Activation on Manual Transmission Vehicles

Fast Idle Warmup can be activated when:

• Coolant temperature is below 140°F.
• Intake manifold temperature is below 15°F.
• The brake pedal is depressed and held for 30 seconds.

Conditions preventing activation:

• Vehicle speed is detected.
• Vehicle speed tampering faults are active.
• Vehicle speed signal faults are active.

For manual transmission vehicles where Fast Idle Warmup activates due to clutch or service brake engagement, ensure the transmission is in neutral before releasing the clutch or brake to deactivate the feature.

For automatic transmissions, Fast Idle Warmup deactivates when the service brake is depressed.

Interaction with Other Features

• Fast Idle Warmup will not activate if PTO is engaged and the load exceeds the set threshold.
• If the PTO load drops below the threshold but later exceeds it, Fast Idle Warmup deactivates.
• If coolant or intake manifold temperature sensor faults are detected, the lowest recorded temperatures since the key switch was turned on are used to determine activation.
• Fast Idle Warmup does not activate if vehicle speed tampering or signal faults are detected.

Adjustable Parameters

Figure 1.2 – Fast Idle Warmup (Features and Parameters)

1. Fast Idle Warmup: Enable or disable via the ECM Value column dropdown.
2. Fast Idle Warmup Idle Speed: Allows fine-tuning of idle speed to reduce vibrations. Default is 1200 RPM.
3. Fast Idle Warmup PTO Load Threshold: Determines the PTO load level required for activation. Default is 10%.

Fast Idle Warmup Test

This test simulates the feature to help determine the most suitable engine speed when active.

Performing the Test:

1. Attach a PC to a running engine in a stationary vehicle.
2. Select Fast Idle Warmup Test from the ECM Diagnostic Tests Wizard and click Next.

Figure 1.3 – ECM Diagnostic Tests Wizard

Figure 1.4 – Fast Idle Warmup Test

1. Ensure engine speed is 600 RPM or higher.
2. Review any displayed messages or warnings.
3. Click Start.

Figure 1.5 – Fast Idle Warmup Test (Value: Inactive)

1. Select Engage to manually test Fast Idle Warmup.
   • A delay of 30 seconds to 5 minutes occurs before the engine speed ramps up.

Figure 1.6 – Fast Idle Warmup (Engage)

1. Adjust the idle speed using the Fast Idle Warmup Speed spin box.
2. Click Adjust to send the speed setting to the ECM.

Special Instructions

Use the Fast Idle Warmup State Monitor to determine ECM commands:

• Inactive: Fast Idle Warmup is not active.
• Delay: ECM is within the activation delay period (30 seconds to 5 minutes).
• Ramp: Fast Idle Warmup is active, and the engine speed is increasing.
• Active: Fast Idle Warmup is fully engaged.

Figure 1.7 – Fast Idle Warmup (Value: Ramp)

Figure 1.8 – Fast Idle Warmup (Value: Active)

Note: ECM changes during testing are temporary. To permanently change Fast Idle Warmup settings, use the Features and Parameters window.

The test runs for a maximum of 15 minutes and stops automatically. The timer box displays elapsed test time.

1. Click Disengage, then Stop to end the test.

Figure 1.9 – Fast Idle Warmup (Disengage)

Figure 1.10 – Test Stopped (Stop)

Click Back to perform a different test.

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