Operation CHARM: Car repair manuals for everyone.
Home >> Porsche >> 2004 >> Boxster S (986) F6-3.2L >> Repair and Diagnosis >> Relays and Modules >> Relays and Modules - Accessories and Optional Equipment >> General Module >> Testing and Inspection >> PCM2/CDR23 Diagnosis >> PCM2/CDR23 CD Changer >> CD Changer Control Module Function

CD Changer Control Module Function



Control Unit Function - CD Changer

Terminating Resistors On The CAN
Terminating resistors are fitted to each end of the wiring to prevent reflection on the wiring. These terminating resistors are integrated into each control module. The interconnection prevents the resistors from being measured with the ohmmeter from the outside.

Replacing An Optical Waveguide
When working on the optical waveguide, attention must be paid to the correct fitting of each diode (transmitter and receiver diodes), otherwise function cannot be guaranteed.

When working on the optical waveguides, please observe the instructions in assembly.
- Fit the diode with the white moulding ('Transmitter diode') on the locking element.
- Fit the diode with the black moulding ('Receiver diode') opposite the locking element.

CAN Comfort
Communication between the Porsche System Tester II No. 9588 and the MOST control modules only takes place via the K lead to the instrument cluster. The data is transferred from the instrument cluster gateway to the MOST control modules, via CAN Comfort to the PCM2 gateway, via the electrical MOST in the PCM2 and via the optical MOST outside of the PCM2.

CD Changer (CDC)
The CDC is available as an optional feature and is linked to the PCM2 via the optical waveguide.

NOTE: When trying to remove the electrical plug connection it may be that, because tolerances are too tight, this cannot be done. In this case remove the holder on the CD changer. Remove the side cover above the electrical plug connection and lift off. Using the appropriate tool between the plug and the housing, carefully make a gap of about one millimeter so that the latch can be disengaged from the cover and the plug can be pulled off.

On the PCB under the cover there is a glass fuse (3 amps); if the CD changer voltage supply fails, check this and replace if necessary.

Coding Table










Data Transfer Fault
If faults are detected when the data is decoded, this is known as a data transfer fault. The faults can arise when the data is encoded, when the data is transferred through an input level that is optically too low or when the data is decoded. A fault entry is not recorded.

Extended Identification
Additional data present in the control unit can be read out using this menu item.
1. Connect and start the Porsche System Tester II No. 9588 and switch on the ignition.
2. Select 'Boxster (986)' in the Vehicle type menu and confirm with the >> key.
3. Select 'PCM' in the control modules selection and confirm with the >> key.
4. Select 'CD changer' in the PCM2 function selection and confirm with the >> key.
5. Select the "Identification" menu item and press the >> key.
6. "Diagnosis software number; PCM2 parts number" appears on the display.
7. Confirm PCM2 GW extended identification with the F8 key or the >> key.

The following data can be read out:
- CRIN (Car Radio Identification Number)
- Date of ECU Manufacturing (YYYY;MM;DD)
- Repair Shop Code or Tester Serial Number
- System Supplier ECU Hardware Number (cw, year)
- System Supplier ECU Hardware Version Number
- System Supplier ECU Software Number (cw, year)
- System Supplier ECU Software Version Number
- Vehicle Manufacturer Diagnostic Index
- Vehicle Manufacturer ECU Hardware Number
- VIN (Vehicle Identification Number)

Function Of The Components







Gateway
The gateway is integrated in the PCM2. Together with the MMI, it is a fixed component of each PCM2. It provides a connection to CAN Comfort via its nodes. Diagnostic and useful data is exchanged with the CAN via these nodes. It creates links to the following systems:
- CAN Comfort
- Media Oriented Systems Transport (MOST), internal (electrical)
- Voice control system (VOCS) (optional/insertion)
- Navigation (optional/insertion)
- Man Machine Interface (MMI)
- Single CD
- Media Oriented Systems Transport (MOST), external bus (optical)

Identification
The diagnosis software number and the part numbers for the PCM2 can be read out under this menu item.
1. Connect and start the Porsche System Tester II No. 9588 and switch on the ignition.
2. Select 'Boxster' in the Vehicle type menu and confirm with the >> key.
3. Select 'PCM' in the control modules selection and confirm with the >> key.
4. Select 'PCM2/CDR23' in the control units selection and confirm with the >> key.
5. Select 'PCM2 GW' in the PCM2 function selection and confirm with the >> key.
6. Select the "Identification" menu item and press the >> key.
7. "Diagnosis software number; PCM2 parts number" appears on the display.

Lock/Unlock
A lock occurs when the signal sent from the MMI via the wake-up/diagnosis distribution line is understood and answered by the connected MOST control modules; this results in a 'lock (connection)'. The lock is maintained until the signal disappears, i.e. an 'unlock' occurs.

Man Machine Interface (MMI)
The MMI is part of the PCM2 (on the mainboard). It carries out the diagnostics of the ring break diagnosis line (stub cable) and the diagnostics of the optical distribution line.

MOST Switch
The MOST switch is part of the PCM2. It keeps the electrical MOST closed if no other MOST control module is optically connected to the MOST. The MOST switch is opened when a light signal is received from the connected MOST control modules.

The following settings can be coded:
- MOST switch open
- MOST switch closed

NOTE:
- When the PCM2 is replaced, the coding must be performed in accordance with the vehicle equipment.
- When the 'Switch closed' parameter is set, the switch remains closed even in existing MOST control modules. Communication is then not possible.

MOST Actual And Required Installed Components Lists
All MOST control modules that are connected to the PCM2 are entered via diagnostic tester in the 'required installed components list'. Only the MOST control units recorded in the MOST required installed components list are activated. An 'actual installed components list' of detected devices is written and saved when the PCM2 is started.

MOST - Optical/Electrical
MOST signals are transferred electrically within the PCM/CDR23 and optically outside of the PCM/CDR23. Internally, the PCM2 consists of at least 2 nodes (GW and MMI), which are installed in the device and can also be expanded to four nodes by adding the navigation and VOCS nodes. Internally, the CDR23 consists of one node (GW) which is installed in the CDR23.

The data is transferred outside of the PCM2 via the optical waveguide, which creates a connection to the nodes in the external MOST control modules such as external amplifiers, CD changers, and/or telephone/telematics (depending on the equipment). The data is transferred outside of the CDR23 via the optical waveguide, which creates a connection to the nodes in the external MOST control modules such as external amplifiers and/or CD changers (depending on the equipment). The gateway node represents the connection to CAN Comfort.

Navigation
The navigation module is designed as a module box, which can be inserted in the PCM2 as an option. After the insertion, an electronic switch is opened automatically and the module is integrated into the MOST ring.

Ring Break Diagnosis Line
The ring break diagnosis line is an electrical lead, which, as a stub cable, connects the individual MOST control modules in the system with one another.

The existing MOST control modules and wiring of the ring break diagnosis line are checked at regular intervals.

Single CD
The CD player is part of the PCM2. It is used to update the navigation system.

Voice Control System (VOCS)
The VOCS is designed as a module box which can be pushed into the PCM2 (optional). After the insertion, an electronic switch is opened and the module is integrated into the MOST ring.

PCM2 Control Module (Head Unit)
The PCM2 control module (head unit) includes the following components:

- Internal:
- PCM2 gateway
- PCM2 Man Machine Interface (MMI)
- Amplifier (internal)
- Tuner
- Single CD
- Navigation (optional/insertion)
- VOCS (voice control system) (optional/insertion)
- Controller Area Network (CAN) Comfort
- MOST switch

- External:
- External amplifier (optional, Harman or BOSE)
- CD changer (CDC), (optional)
- Telephone/telematics (optional)

The PCM2 consists of at least two but a maximum of four MOST nodes, (Gateway, MMI and Navigation and VOCS (optional)), which communicate with each other electronically via the MOST. Data is transferred outside of the PCM2 via the optical MOST.

Input Signals
The following queries can be run using this menu item:
- 3 dB lowering

NOTE: Deactivate the 'automatic traffic announcement' before performing the diagnosis on the PCM2. If this is not done, the diagnosis will abort.

Menu item Function

- 3dB lowering Under this menu item, it is possible to check the electrical and optical MOST during troubleshooting.
- Connect and start the Porsche System Testing II No. 9588 and switch on the ignition.
- Select 'Boxster' in the Vehicle type menu and confirm with the >> key.
- Select 'PCM' in the control modules selection and confirm with the >> key.
- Select 'PCM2/CDR23' in the control units selection and confirm with the >> key.
- Select 'PCM2 GW' in the PCM2 function selection and confirm with the >> key.
- Select the Input signals menu item and press the >> key.
- Select "3dB lowering" menu item using the > and press the >> key.
- Read out values from the display field.

Telephone/Telematics
The telephone/telematics feature is available as an option and is linked to the PCM2 via the optical waveguide.

Tuner
The tuner is part of the PCM2 (on the main board).

Unlock Counter
Interruptions occur in the system if perfect communication is no longer possible. If the relevant threshold values are exceeded, an entry is recorded in the appropriate control module and the 'unlock counter' is incremented.

External Amplifier
The external amplifier (Harman or BOSE) is available as an optional feature and is linked to the PCM2 via the optical waveguide.

Internal Amplifier
The internal amplifier is part of the PCM2 (installed on the main board).

Wake-Up Function
All control units connected to the MOST are in sleep mode if the PCM2 is deactivated. When the PCM2 is switched on, a 'light' is switched on via the MMI. It is reinforced and passed on by the MOST control modules that are connected.
pro multis · About Operation CHARM