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(TA521-0608) ESP out of function

TECHNICAL ADVICE - Quick information for your help
Bulletin Nbr: TA521-0608
Date: ........... May 2006
Market: aLL
ESP out of function

VEHICLES CONCERNED

Saab 9-3 Sport Sedan, Convertible M03-M05.

BACKGROUND

Every sensor has a kind of natural offset caused by the ingoing components and their tolerance in combination with tolerance from the production process. This offset of the sensors should be in a certain range and fulfill the specification from GME.

In some cases ,when the sensor offset is on the edge of the specification AND the starting position of the vehicle (in which the sensor is installed in) has a certain inclination, this situation can lead to that the ESP system is switched off.

CONDITIONS

Continuos problems after fault tracing and after exchange of Yaw Rate sensor(-s).


• Fault codes C0186 00 and/or C0186 11.

• MIU: TCS OFF or ESP OFF

• SID: Anti-spin/Anti-skid not functioning.

• Message in SID: Contact a workshop. The symbol and text are displayed when system fault is detected.


SYMPTOM DESCRIPTION

ESP indication and in some cases fault code C0186 00 and/or C0186 11 are set.

ACTION

To solve this issue as easy as possible, is to measure the "built in" offset of the (lateral acceleration) sensor in that specific vehicle and "tilt" the sensor to receive a mechanical offset compensation. I.e possibilities to correct the lateral acceleration sensors raw values.


Necessary parts and tools:

• Proposal for nut washer dimensions:

Due to that its not possible to give the lateral acceleration sensor an absolute "zero" position =(0m/s²), the focus should be to have the corrections in controlled range of e.g.+/- 0,1 m/s². Washers with dimension which fits on a M6 bolt and max diameter of 20mm in steps of 0,5mm thickness (i.e 0,5mm;1,0mm;1,5mm....)

• Geometrical relations about "tilting the sensor" Tilting the sensor to either direction will automatically change the (raw value) sensor offset. Depending on the measured offset a correction can be done by adding nut washer on the respective side under the sensor.

• Placing nut washers under the left (2 bores) will "add" a value to the sensor offset.


• Placing a nut washer under the right (1 bore) will "subtract" a value from the sensor offset.


Geometrical relations and calculated values:

As a definition the relationship 1 m/s² = 5,7° is known and used in the following calculations. Using the trigonometric functions, the thickness of the nut washer (to fill the gap) can be calculated, to compensate the sensor offset. The pictures are seen from the back side of the sensor i driving direction.

+ Enlarging to the measured offset

- Reducing to the measured offset


Compensation values with tilted sensor:




How to proceed:

Park the car in a plane horizontal place and measure the "natural" lateral acceleration sensor offset (ESP/read values"LATERAL ACCELERATION SENSOR") with the TECH II tool.

Disassemble center console and gearshift module and dismount the sensor.

In case of a negative signed value in [m/s²]

Add nut washer on the right bolt (1psc) in respective thickness to compensate the offset by giving the sensor a defined inclination.

Mount the sensor and check with the TECH II if the offset has disappeared or has moved enough towards zero (between 0,09 to 0 is ok)

In case of a positive signed value in [m/s²]

Add nut washers on the left bolts (2 pieces) in respective thickness to compensate the offset by giving the sensor a defined inclination.

Mount the sensor and check with the TECH II is the offset has disappeared or has moved enough towards zero.

Assemble center console and gearshift module.