B1390

Fig. 22 Code B1390: Wheel Sensor, Wrong Number Of Teeth (Part 1 Of 2):

Fig. 22 Code B1390: Wheel Sensor, Wrong Number Of Teeth (Part 2 Of 2):

Fault symptom
ABS warning lamp on, no ABS function.

Condition
The wheel speed is compared to a reference speed (= filtrated mean value of all wheel speeds).
- a wheel speed 25% higher than the reference speed for 20 seconds
- Two wheel speeds 6% higher than the reference speed for 20 seconds.
- a wheel speed <6% lower than the reference speed for 2O seconds, or two wheel speeds for 10 seconds.
- Continual ABS modulation for more than 60 seconds.

Diagnostic help
- Any particular wheel speed sensor can be read by the ISAT Scan Tool.
- Select "READ FUNCTIONS"
- Select "WHEEL SPEEDS"
The current wheel speed in km/h is displayed.

Diagnostic procedure
1 Diagnostic Trouble Code inspection
- Connect the ISAT Scan Tool.
- Start and test drive the car at an even speed. Read WHEEL SPEEDS according to the Diagnostic help. Compare the four displayed wheel speeds.
All wheel speed ratings should be the same.

Does the ISAT display the correct rating?
YES - Continue with point 2.
NO - Displays FL faulty reading, continue fault diagnosis according to B1371.
Displays FL faulty reading, continue fault diagnosis according to B1376.
Displays FL faulty reading, continue fault diagnosis according to B1381.
Displays FL faulty reading, continue fault diagnosis according to B1386.

2 Final inspection
- Erase the diagnostic trouble code.
- Carry out the driving cycle, drive the car with various load and engine speeds for 5 minutes.
- Read the diagnostic trouble code,

Is the diagnostic trouble code stored?
YES - Continue on "Test Procedure Prior To Replacing ECM"
NO - The diagnostic procedure performed is right or the fault is of intermittent character.