Checking Incorrect Engagement of Four-Wheel Drive
Checking incorrect engagement of four-wheel drive
Fault-tracing information
Differential electronic module (DEM) checks engagement and disengagement of four-wheel drive. The control module controls engagement and disengagement using a number of parameters, among others, by comparing speed of the wheels. If the vehicle's tires are worn unevenly (compared front and rear, or if a tire with incorrect dimension is installed (compared with the vehicle's other tires) on the vehicle's front or rear axle, this may result in incorrect engagement of four-wheel drive. Incorrect engagement of four-wheel drive may be experienced as jerk or hack when driving.
Incorrect engagement is if four-wheel drive is activated at a time when the following parameters are fulfilled:
- Constant vehicle speed (above 20 km/h).
- Constant engine rpm.
- Brake pedal released (no braking).
- The parking brake is not applied.
- Engine brake not active (accelerator pedal pressed down).
Causes of interference can be:
- Unevenly worn tires (compared front and rear).
- Tire with incorrect dimension has been installed on front or rear axle (compare with other tires on the vehicle).
Continue - Checking tire wear
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Checking tire wear
Check tires for wear. The tires shall be worn evenly when comparing front and rear. Check that all tires have the same dimension. If any or some tires are more worn than the others or have a different dimension, it is recommended that these are replaced.
Continue - Checking software version
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Verification
Information
Fault-tracing information
In case of this defect, troubleshooting is not followed by verification.
The information can be displayed again or the fault-tracing for this fault can be interrupted.
Do you want to view the information again?
Yes - Attempt New Test
No - Exit fault-tracing
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Attempt New Test - Fault-tracing information
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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 - Fault-tracing information
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Checking software version
From and incl. week 39 year 2007, there is software with greater tolerance for different wheel speeds, this to minimize the risk of incorrect engagement of four-wheel drive at, e.g., slightly unevenly worn tires. The rolling circumference may vary slightly even on new tires.
Check if new software is available for download in Differential electronic module (DEM).
Continue - Test driving and reading off diagnostic trouble codes (DTCs)
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Test driving and reading off diagnostic trouble codes (DTCs)
After changing tire and/or new software has been downloaded in the control module, the vehicle shall be test-driven and then read out with VIDA. Before test-driving, connect VIDA and read out parameter "Number of detections of malfunction condition" via CARCOMMUNICATION/Parameters. Note the quantity.
Test-drive the vehicle and fulfill the following criteria at the same time at least once:
- Constant vehicle speed (above 20 km/h).
- Constant engine rpm.
- Brake pedal released (no braking).
- Engine brake not active (accelerator pedal pressed down).
After test-driving:
Connect VIDA and read out parameter "Number of detections of malfunction condition" via CARCOMMUNICATION/Parameters. Compare the number before and after test-driving, if the number of "detections of malfunction condition" is higher after test-driving it indicates that Differential electronic module (DEM) has detected "incorrect engagement" of four-wheel drive.
The parameter "Number of detections of malfunction condition" is only counted up once per driving cycle if "incorrect engagement" is detected.
Has the counter counted up after test-driving?
Yes - Fault-tracing information
No - Verification
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