Test AH: Visctronic Drive Fan (VDF)
PINPOINT TEST AH: VISCTRONIC DRIVE FAN (VDF)Flow Chart (Part 1):
Flow Chart (Part 2):
WARNING: To avoid the possibility of personal injury or damage to the vehicle, do not operate the engine until the fan blade has been first examined for possible cracks and separation. Failure to follow these instructions may result in personal injury or death.
This pinpoint test is intended to diagnose the following:
- VDF
- fan speed sensor
- harness circuits
- powertrain control module (PCM) (12A650)
VDF Connector
VDF Connector:
PCM Connector
PCM Connector:
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AH1 : PRELIMINARY DIAGNOSIS
- Ignition ON, engine OFF.
- Record the freeze frame data.
- Carry out the PCM self-test.
- Are any DTCs present?
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AH2 : CHECK THE COOLING FAN FOR MECHANICAL BINDING
NOTE: The VDF is a viscous coupling. The viscous drag should be smooth during fan rotation. The amount of resistance is dependant upon the final VDF operational state before engine shutdown.
- Ignition OFF.
- Manually rotate the cooling fan.
- Does the fan clutch rotation feel rough or binding?
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AH3 : CHECK THE VDF OPERATION
NOTE:
- Check and verify the most current PCM calibration level.
- Inherent to viscous clutches is a delay in transitioning from a low to a high speed or from a high to a low speed. This delay can vary between 10 seconds and 3 minutes and is dependant upon engine speed and clutch temperature. With the engine at operating temperature and at 2,500 RPM, the delay should be less than 30 seconds.
- The calibration limits the engine RPM when using output state control. The engine RPM must be increased using the accelerator pedal to reach the required RPM for this test.
- Ignition ON, engine running.
- Access the PCM and monitor the FANSS PID.
- Access the PCM and monitor the RPM PID.
- Increase the engine speed to 2,500 RPM using the accelerator pedal.
- Access the PCM and control the FANVAR PID.
- Control the FANVAR duty cycle to LOW.
- Allow the fan speed to stabilize below 600 RPM.
- Control the FANVAR duty cycle to HIGH.
- Does the fan speed change and does the FANSS PID indicate an RPM change?
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AH4 : CHECK THE VDF SOLENOID RESISTANCE
- Ignition OFF.
- Cooling Fan Clutch connector disconnected.
- Measure the resistance between:
- Is the resistance between 6 Ohm - 10 Ohm?
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AH5 : CHECK THE VDF SOLENOID FOR A SHORT TO GROUND
- Measure the resistance between:
- Is the resistance greater than 10 kOhm?
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AH6 : CHECK THE VDF SOLENOID VPWR CIRCUIT FOR VOLTAGE
- Ignition ON, engine OFF.
- Measure the voltage between:
- Is the voltage greater than 10.5 V?
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AH7 : CHECK THE VDF SOLENOID CONTROL CIRCUIT FOR AN OPEN
- Ignition OFF.
- PCM connector disconnected.
- Measure the resistance between:
- Is the resistance less than 5 Ohm?
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AH8 : CHECK THE VDF SOLENOID CONTROL CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between:
- Is the resistance greater than 10 kOhm?
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AH9 : CHECK THE VDF CONTROL CIRCUIT FOR A SHORT TO POWER
- Ignition ON, engine OFF.
- Measure the voltage between:
- Is any voltage present?
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AH10 : CHECK THE FAN SPEED SENSOR FOR VOLTAGE
- Ignition OFF.
- VDF connector disconnected.
- Measure the voltage between:
- Is the voltage greater than 10.5 V?
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AH11 : CHECK THE VBPWR CIRCUIT FOR VOLTAGE
- Measure the voltage between:
- Is the voltage greater than 10.5 V?
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AH12 : CHECK THE VBPWR CIRCUIT FOR AN OPEN
- Ignition OFF.
- PCM connector disconnected.
- Measure the resistance between:
- Is the resistance less than 5 Ohm?
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AH13 : CHECK THE VBPWR CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between:
- Is the resistance greater than 10 kOhm?
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AH14 : CHECK THE FAN SPEED SENSOR FSS SIGRTN CIRCUIT FOR AN OPEN
- Ignition OFF.
- PCM connector disconnected.
- Measure the resistance between:
- Is the resistance less than 5 Ohm?
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AH15 : CHECK THE FAN SPEED SENSOR SIGNAL CIRCUIT FOR AN OPEN
- Ignition OFF.
- PCM connector disconnected.
- Measure the resistance between:
- Is the resistance less than 5 Ohm?
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AH16 : CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between:
- Is the resistance greater than 10 kOhm?
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AH17 : CHECK THE SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition ON, engine OFF.
- Measure the voltage between:
- Is any voltage present?
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AH18 : CHECK THE SIGNAL CIRCUIT FOR VOLTAGE
- Ignition OFF.
- PCM connector connected.
- Ignition ON, engine OFF.
- Measure the voltage between:
- Is the voltage greater than 10 V?
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AH19 : CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Visually inspect for:
- pushed out pins
- corrosion
- Connect all the PCM connectors and make sure they seat correctly.
- Carry out the PCM self-test and verify the concern is still present.
- Is the concern still present?
