Initial Inspection and Diagnostic Overview
Power Seat Module
System overview
Control module
The task of the power seat module is to manage the following functions:
- Seat maneuvering
- Storage of memory positions (seat positions only).
The control module is under the seat on the driver's side. The seat must be removed in order to replace the control module.
The power seat module is directly connected to components and to other control modules via CAN communication.
The control module checks activations and input and output signals through an integrated diagnostic system. A diagnostic trouble code (DTC) is stored in certain cases if the control module detects a fault.
Diagnostic trouble codes (DTC) are stored in the control module memory. The data can be read off using the diagnostic tool.
A simple way to check that the power seat module (4/52) is supplied with power and grounded is to move the seat.
If the voltage is below 8.5 V or above 16.0 V the power seat module will not function. If the voltage increases to 9.0 V or falls to 15.5 V the control module will function again.
Signals
The table summarizes input and output signals to and from the power seat module (4/52). The signal types are divided into directly connected signals, serial communication and Control area network (CAN) communication. The illustration displays the same information with the Volvo part numbers.
Design
Control panel
There are two different types of control panels. In cars with power seats without memory, the control panel is directly connected to the motors and does not have a power seat module.
In cars with power seats and memory, the control panel is directly connected to the power seat module. An easy way of differentiating between power seats with memory (power seat module) and power seats without memory is to look at the control panel. Seats without memory do not have memory buttons 1-3 or a programming button.
This information refers to seats with memory (power seat module) unless otherwise stated.
The control panel is connected to the power seat module via wiring that is integrated in the control panel. The entire control panel must be replaced if there is a fault with the wiring or the panel.
The panel is used to transmit input signals to the control module from the user:
- Runs each of the four motors in the direction required
- Memory buttons. Input signal indicating the position of the buttons (Memory 1, 2 and 3 and the programming button)
- Ground
- To detect that a control panel is connected to the control module.
If there is no supply to the control panel, because of an open-circuit in the cable for example, the control module will not register any input signals from the control panel. If a cable breaks only that function will fail. For example Memory 1 cannot be programmed but the other memories are functioning.
The wiring cannot be replaced separately. The entire control panel must be replaced if there is a fault.
The control panel can be diagnosed.
Function
Seat programming
There are four buttons for programming seat positions. There are three memory buttons, 1, 2 and 3 and a programming button, MEM.
To program a new seat position, move the seat to the desired position and press MEM and one of the memory buttons at the same time.
To move the seat to a programmed position press and hold down the desired memory button. The button must be kept depressed for the seat to move. The seat stops if the button is released.
The seat stops moving when the position of the seat matches the position programmed into the memory. If another button is pressed the seat will stop moving. The seat will not move if no position is programmed.
If the car was built in structure week 9950 or later, the car has door mirrors with memories. When the desired memory button is pressed, the mirrors and seat are set to the desired positions. Data is sent from the power seat module (4/52) to the passenger door module (3/126) (3/127) to set the door mirrors to the programmed position. The memory positions of the door mirrors are stored in the driver's door module (DDM) (3/126) and passenger door module (PDM) (3/127). When setting a new mirror position, this is stored in each control module. The position of the driver's door mirror is stored in the driver door module (DDM). The position of the passenger door mirror is stored in the passenger door module (PDM).
When the seat is run, a maximum of two motors are activated at the same time. If all motors need to operate to reach the programmed position, there is an order of priority. Motor 1 (front-rear adjustment) and Motor 2 (backrest adjustment) operate first.
Each seat motor has a Hall sensor which detects the current seat position. When one of the stepper motors for the seat is run, the control module counts the number of pulses from the Hall sensor. The Hall sensor counts the number of revolutions made by the motor by detecting a magnet on the motor shaft. This creates a pulse for each revolution of the motor.
When a seat position is stored, information about the number of pulses recorded from each motor is stored in a memory, allowing the position of the seat to be saved.
When one of the memory buttons is pressed in, the control module calculates which motors need to be run and in which direction to obtain the desired position.
Maneuvering seats with memory
On a power seat, the backrest can be adjusted, the seat height can be altered and the seat can be moved forwards or backwards. There are four motors for moving the seat. The control buttons are on the outside of the seat and are in the shape of a small seat and a small backrest. There are two control buttons on each panel. The buttons are spring loaded, so they must be held pressed in for the seat to move.
The seat can be maneuvered:
- Within a period of 9 minutes and 40 seconds of the door being opened
- Within 40 seconds of the door being closed
- With the key in the radio position
- With the ignition on.
Remote operation of seats
There are three memories in the power seat module (PSM) which store the seat positions for a maximum of 3 remote controls. There are also three further memory positions which can be stored from the control panel. The seat can store a total of six different memory positions.
Cars with power seats with memory have a personal setting function. Using this function, the positions of the mirrors and seat can be stored individually for each remote control (a maximum of three remote controls, i.e. remote memory positions 1, 2 and 3).
The customer parameters in the power seat module (4/52) determine whether the remote memory for the seat is activated or not.
From model year 2003 inclusive the remote control memory for the mirrors can also be switched off. This is done using a customer parameter in the driver's door module (DDM) (3/126) and passenger door module (PDM) (3/127). "Programming of the remote control settings" for seats and mirrors is carried out via VADIS/VIDA vehicle communication.
The signal from the remote control is transmitted to the upper control module (UEM) (4/70) when the car is locked or unlocked. The upper electronic module (UEM) also identifies which remote control is being used. The central electronic module (CEM) (4/56) receives this information from the upper electronic module (UEM). The central electronic module (CEM) identifies and stores the remote control which is being used and determines the data to be sent to the power seat module (PSM) (4/52), driver door module (DDM) (3/126) and passenger door module (PDM) (3/127). This is done when the door is opened.
For model year 2003 the central electronic module (CEM) transmits information about which remote control locked the car.
From model year 2003 inclusive, the central electronic module (CEM) transmits information about which remote control locked the car and which unlocked the car.
If the position of the seat is changed, the power seat module (PSM) (4/52) stores the new position before reverting to sleep mode.
Remote memory positions are stored in the power seat module (PSM) in the following cases:
- 10 minutes after the door has been opened
- 1 minute after the door has been closed
- With the ignition off
- When the key is removed from the ignition switch
- When a new remote control is activated.
The remote memory positions for the door mirrors are stored for the driver door module (DDM) and passenger door module (PDM) in the following cases:
- When the key is removed from the ignition switch
- When a new remote control is activated.
When the car is unlocked, the power seat module (PSM) uses the information about which remote control unlocked the car. This is so that the correct remote memory position can be selected (i.e. the seat position last set by the driver for this remote control). When the door is opened the seat starts to move to the programmed remote memory position. The seat can be stopped by pressing one of the buttons on the control panel.
If the car is opened with a key, the memory settings for the seat are not affected. Remote operation of the seat is not possible if the key is in the ignition switch.
On model year 1999-2002 cars, the system may exhibit unwanted properties. Only information about which remote control unlocked the car is transmitted, a new memory position is not stored if the car was unlocked before this. This is because when a car door is opened and the power seat module (PSM) switches into active mode, the module is unable to identify which remote control is being used.
In addition, when a door is open, it takes 10 minutes before the power seat module (PSM) switches to sleep mode. If this occurs, and the customer then attempts to set a new seat position, the information about which remote control opened the door will have been lost and a new memory position will not be stored.
Maneuvering seats without memory
Power seats without memory do not have memory management buttons. The seat motors can only be operated directly via the control panel. This type of seat does not have a power seat module (PSM). The seat motors are directly connected to the control panel.
Power seat module diagnostic functions
General
The control module has a built-in diagnostic system, the Volvo on-board diagnostic (OBD) system, which continuously monitors itself and its input and output signals.
Diagnostic trouble codes (DTCs)
If the control module detects a fault it will store a diagnostic trouble code (DTC). A fault which is detected in the latest driving cycle is defined as permanent. Other detected faults are defined as intermittent.
Reading and erasing diagnostic trouble codes (DTCs)
Stored diagnostic trouble codes (DTCs) can be erased using this function.
Erasing diagnostic trouble codes (DTCs) can only be carried out when all diagnostic trouble codes (DTCs) have been read at least once.
Reading off control module identification
VADIS/VIDA identifies the control modules by reading off a number of codes from control module memory.
The codes contain information about control module:
- P/N hardware (control module without software)
- serial number hardware (control module without software)
- P/N software
- P/N diagnostic software
Downloading software and replacing the control module
New software can be downloaded into the power seat module. When ordering software, the hardware and the software in the car is compared to the Volvo central database. If the comparison is OK the software is downloaded to the control module.
If the comparison between the car and Volvo central database does not correspond, the database is updated with the configuration of the car. New software is downloaded after the update is complete.
A control module may already have software installed which will result in incorrect information being updated on Volvo's Central Database. To avoid this, tick the box in the VADIS/VIDA software manager indicating the software has been replaced when the control module has been replaced.
A number of customer parameters can be programmed into the power seat module. These customer parameters are stored in the control module but not in the Volvo central database. This means that the customer parameters must be reprogrammed when the hardware is replaced and when downloading software.
The power seat module calculates the current required by the motors. A current limit can be set to protect the wiring from high currents.
- There is a parameter which detects when the seat has reached its limit position, in other words blocked motor. (Programmable)
- There is a parameter for detecting short-circuits (Can be read off).
The value of the current for a blocked motor can be set using the diagnostic tool. When programming, the value of the blocked motor must be less than the value for a short-circuit. If this is not the case, the control module will indicate a short-circuit in the cable when the seat is run to its limit position.
The motor stops when the current exceeds the value for a blocked motor and the control module registers no pulses from the Hall sensor. The level of current for a blocked motor can be set between 9 and 20 Amperes.
It is possible to reprogram the function so that the seat is automatically set by remote control. With this function activated the seat can be set using the remote control. This function is removed if it is deactivated.