Test Point 2

Test point 2

Front left speed sensor, signal implausible DTC 4206
Control module receives a false / unrealistic speed sensor signal.

Procedure:
Check the speed sensor signal with the System Tester 2 via the "Actual values" menu. To do this, call up the front left wheel speed.

Two tests are possible here.
Test 1 with raised vehicle.
(Swap of speed sensors and test of the speed sensor signal quality.)

Test 2 with vehicle driving straight at approx. 2 - 4 km/h. (Comparison of wheel speed signal qualities with each other.) Test 2 is a better measure of the signal quality than is test 1.

Further to test 1
To perform the test, manually rotate the left front wheel at a speed of approx. 2 - 3 km/h (observe display in the Tester screen). Slowly increase the speed and simultaneously observe the speed increase (display).

Nominal values/required display
Speed steps of approx. 0.06 km/h. First display at 1.81 km/h. This means: From the value measured last, the next value must be 0.06 km/h higher or, if the wheel is rotating slower, must be 0.06 km/h lower.The Tester rounds the value down to 0.05 km/h or up to 0.07 km/h in some cases.

Example
First measured value = 1.81 km/h
Second nominal value = 1.87 km/h
Third nominal value = 1.93 km/h
etc.

Further to test 2
Display all four wheels in the Tester display. Drive straight ahead at a uniform speed of approx. 2-4 km/h and have a second person observe the Tester display. Required display: Deviation between the wheel speeds of the four wheels max. 1 km/h.

Further details about tests 1 and 2 are given under "Actual values menu".

Possible faults (cause in the event of deviation):
1. Air gap between speed sensor and gear wheel (pulse wheel) too large or, due to wear (chip formation), too small (check installation).
2. Pulse wheel defective or corroded.
3. Wheel bearing damage (wheel bearing not adjustable).
4. Plug connection in wiring from the speed sensor to the control module or PIN on the control module connector not OK.