The Engine Speed (RPM) Oscillates
The engine speed (RPM) oscillates
Checking the neutral check
- Ignition off.
- Check transmission connectors A and B and the transmission control module (TCM) connector for contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
- Reconnect the connectors, reinstall components etc.
- Raise the car so that the drive wheels are unimpeded.
- Start the car.
- Move the gear selector to position D and accelerate so that the speed exceeds 50 km/h.
- Brake the wheels and let the engine run at idling speed without touching the accelerator pedal (AP). The neutral check should display "Active" status (this may take up to 30 seconds).
- Brake the wheels, move the gear selector to position D. Carefully depress the accelerator and check that the neutral check changes to the "Inactive" status.
The engine speed (RPM) should be even when transferring from Active to Inactive status.
Check that the function operates in gear positions 4, 3 and 2.
Is the transmission function OK ?
Yes - Test driving
No - Checking solenoid SLT
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Checking solenoid SLT
Note! The transmission must not be colder than room temperature when activated.
- Ignition on.
- Activate solenoid SLT.
The solenoid should"click" on activation (use a stethoscope to hear the sound more clearly) and the current should oscillate between 0 and 1 A. If no " click" is heard this indicates that there is a mechanical fault.
Was solenoid SLT OK?
Yes - Test driving
No - Replacing the transmission
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Test driving
- Ignition off.
- Reconnect the connectors, reinstall components etc.
- Test drive the car according to Verification Neutral Check.
Check that the shifts and the neutral check function without any problems.
Other information
- To access transmission connectors A and B, see Replacement Of Control System Cable Harness With Oil Temperature Sensor.
- To access the control module connector, see Connecting the breakout box, B5234T9, B5244T7 Connecting The Breakout Box.
Is the transmission operating correctly?
Yes - FAULT FOUND
No - Replacing the transmission
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Replacing the transmission
Hint: Transmission AW 50-55 must be replaced in the event of internal faults during the first year on the market.
- Ignition off.
Replace the transmission according to Removing the transmission Transmission, Removal.
Continue - Resetting the adaptation and oil quality counter
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Resetting the adaptation and oil quality counter
Resetting the adaptation
Resetting adaptation and the counter for "Transmission oil change"
Hint: The transmission has torque controlled adaptive pressure control. Pressure control means that the transmission regulates the pressure itself during each gear shift. This avoids harsh gear shifting. Each gear shift is evaluated by the control module and stored in the memory. This allows for compensation for wear and tear in the transmission and clutch. It is important that the adaptation in the memory is reset after the transmission has been repaired. This is to ensure normal operation. The oil is replaced during repair; the "Transmission oil change" counter must be reset. If the counter is not reset when the fluid is drained and replaced, there is a risk that a diagnostic trouble code (DTC) will be stored in incorrect circumstances.
Note! This applies only if the transmission or one of the components in the transmission have been replaced.
- Ignition on.
Click on the VCT2000 symbol to reset the adaptation and counter.
Continue - DONE
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DONE - Verification
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Verification
Verification
Hint: After carrying out the repair, check that the fault has been remedied.
- Ignition off.
- Reconnect the connectors, reinstall components etc.
- Raise the car so that the drive wheels are unimpeded.
- Start the car.
- Move the gear selector to position D and accelerate so that the speed exceeds 50 km/h.
- Brake the wheels and let the engine run at idling speed without touching the accelerator pedal (AP). The neutral check should display "Active" status (this may take up to 30 seconds).
- Brake the wheels, move the gear selector to position D. Carefully depress the accelerator and check that the neutral check changes to the "Inactive" status.
Check that the function operates in gear positions 4, 3 and 2.
Is transmission function OK ?
Yes - VERIFIED
No - VERIFICATION FAILED
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VERIFICATION FAILED - Fault-tracing information
VERIFIED - FAULT FOUND
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Fault-tracing information
Information
Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.
Do you want to exit fault-tracing?
Yes - Exit fault-tracing
No - Attempt New Test
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Attempt New Test - Checking the neutral check
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