Tire Pressure Module: Description and Operation
GF4015-P-5124SX Tire Pressure Monitor Control Unit, Component Description
MODEL 216.3, 221.0 /1 with CODE (475) Tire pressure monitor (Siemens)
MODEL 216.3, 221.0 /1 with CODE (470) Tire pressure monitor (base)
MODEL 216.3 with CODE (494) USA version
Location
The TPM [RDK] control unit is located in the passenger footwell.
Design
The TPM [RDK] control unit consists of a HF-receiver module, a control unit circuit board with microprocessor control and an interface for the Controller Area Network (data bus/CAN Bus) CAN data bus.
Task
Tire temperature is taken into account in the comparison of the tire pressure currently determined by the respective sensor with the stored specified pressure. The TPM [RDK] control unit calculates the valid limits for the current tire temperature. If these limit values are dropped below, then depending on the pressure deviation the TPM [RDK] control unit passes on a corresponding CAN signal to the instrument cluster (A1). This CAN signal is processed in the instrument cluster and the appropriate information is displayed for the driver on the multifunction display (A1p13). The TPM [RDK] control unit also constantly monitors all input and output signals for faults. Detected faults that are relevant to function are entered into the fault memory.
The tire pressure monitoring system control unit receives information from the following sensors via a radio frequency (RF) line from the tire pressure monitoring system antenna (A2/97):
- Left front TPM [RDK] wheel sensor (A69/1/)
- Right front TPM [RDK] wheel sensor (A69/2/)
- Left rear tire pressure monitor sensor (A69/3)
- Rear right tire pressure control wheel sensor (A69/4)
On vehicles with the code (475) Tire pressure monitor (Siemens) the TPM [RDK] control unit is connected to the following components via the local interconnect network (LIN):
- Left front tire pressure monitor antenna (A2/44)
- Right front TPM [RDK] wheel antenna (A2/45)
Upon request from the TPM [RDK] control unit the wheel antenna transmit in sequence a trigger signal to the respective wheel sensor. The wheel sensors then transmit a transmission protocol to the TPM [RDK] via the central TPM [RDK] antenna. These transmission protocols are required for wheel sensor determination after system activation.
In system operation the wheel sensors automatically send the transmission logs at specific intervals.
The transmission logs also contain the following data:
- Tire inflation pressure
- Tire interior temperature
- Wheel acceleration
- Individual sensor ID
- Condition of sensor battery
Via the Controller Area Network (data bus/CAN bus) (CAN) a data exchange takes place with the following control units and controls:
- Instrument cluster, via the central-CAN
- Front SAM control unit with fuse and relay module (N10/1) via the interior CAN
- EIS [EZS] control unit (N73)
- Central gateway control unit (N93), via the interior CAN
- Steering column module (N80), via the chassis CAN
- ESP control unit (N47-5), via the chassis CAN
- CDI control unit (N3/9) (model 221.0/1 with engine 629 or engine 642)
- ME-SFI [ME] control unit (N3/10) (model 216.3, model 221.0/1 except engine 629 or engine 642)
Note: The central gateway control unit forms the interface between the interior CAN, the chassis CAN and the central CAN.
The following information from other systems is processed here:
SAM control unit with fuse and relay module
- Outside air temperature
EIS [EZS] control unit
- Status of circuit 15
CDI control unit (model 221.0/1 with engine 629 or engine 642)
- Status of circuit 61
ME-SFI [ME] control unit (model 216.3, model 221.0/1 except engine 629 or engine 642)
- Status of circuit 61
Steering column module
- Steering angle via steering angle sensor (N49)
- Signals from the left multifunction steering wheel button group (S110) and right multifunction steering wheel button group (S111)
ESP control unit
- Wheel speed of the respective wheel
Central gateway control unit
- Country code
- Engine/body variant
- Diagnosis
The following information is issued to other systems:
Instrument cluster
- Actuation of tire pressure monitor warning lamp (A1e66)
- The measured tire pressure
- Information for display messages
Central gateway control unit
- Diagnosis