General DME 7.8

Introduction

General
The target group is trained automotive workshop personnel who have successfully taken part in Porsche technical training on the systems concerned and possess the necessary theoretical and practical knowledge to be able to carry out work on complex systems.

The basic requirement of all DME work is awareness and observance of safety instructions and warnings; these can be found in the "Notes" on the following.

NOTE: The following troubleshooting diagnosis is aimed exclusively at lefthand drive vehicles and describes only these vehicle types. In some cases, specified plugs and sockets may be assigned differently in right-hand drive vehicles, which can lead to incorrect interpretations during troubleshooting and to unforeseen accidents. Therefore, no work should be performed on right-hand drive vehicles without the correct wiring diagram and troubleshooting diagnosis description.

This OBDII Manual DME 7.8 applies to the following vehicles:
- 911 (996) with turbo engine as of model year 2001
- 911 (996FL) with aspirated engine as of model year 2002
- Boxster (9 Power Of 86FL) with aspirated engine as of model year 2003

The diagnosis and troubleshooting for the engine control module installed in Porsche sports cars (OBD = On-Board Diagnosis). Described are the naturally aspirated engine and Turbo OBD II versions (USA), which cover the full scope of diagnosis. This includes the EOBD (European OBD) and RoW (Rest of World) versions, which have been adapted to the respective laws and regulations from the point of view of diagnostics.

The main differences of versions OBD II and EOBD are the tank leak test legally required in den USA and the criteria for fault memory entry and activation of the CHECK ENGINE lamp (hereafter abbreviated CE), which is also designated as MIL (Malfunction Indication Light).

The following functions are guaranteed by the OBD II system:
- Detection of misfires
- Monitoring of catalytic converter efficiency
- Monitoring of tank ventilation system
- Monitoring of tank system for leaks
- Monitoring of secondary air injection
- Monitoring of adaptation limits (e.g. of oxygen sensor closed-loop control, boost pressure control)
- Monitoring of oxygen sensors
- Monitoring of thermostat and water temperature sensor
- Monitoring of positive crankcase ventilation (via oxygen control adaptation)
- Monitoring of Tiptronic transmission control unit
- Monitoring of emission-relevant sensors and actuators used in conjunction with DME (earlier OBD 1 scope)
- Activation of Check Engine lamp and fault storage
- Display of inspection readiness (readiness codes)
- Output of fault codes present
- Storage of defined operating parameters in the event of a fault (incl. freeze frame)
- Functional tests of OBD system (warm-up cycle, driving cycle)
- Communication with a standardised control module tester (scan tool) in the specified modes
- Standardised output of operating data such as engine speed, temperature etc.

The digital engine control module DME 7.8
The DME 7.8 is a proven and highly reliable engine control module, which has been specially adapted to Porsche requirements.

In the event of an open circuit in the voltage supply 'terminal 30', the following values are deleted from the control module:
- All fault memory entries
- Stored freeze frames of the faults
- All adaptation values
- The learned values of the throttle adjustment unit
- Ready statuses of individual diagnosis routines

Please note that programming the DME control module (e.g. reading in a new data record) also deletes the values referred to above.

Note on adaptation
The DME control module must perform a learning and adaptation routine for the throttle adjustment unit if:
- The power supply to the DME control module is interrupted
- The DME control module plugs are disconnected
- A new DME control module is installed
- The throttle adjustment unit is replaced
- The DME is programmed.

To do this:
1. Switch the ignition on for 1 minute without starting the engine. Do not actuate the accelerator pedal (for instance, make sure that there is not a carpet pressing on the pedal).
2. Switch off ignition for at least 10 seconds.

The following conditions must also be observed, otherwise learning is not possible:
- Vehicle is stationary
- Battery positive voltage between 10 V and 16 V
- Engine temperature between 5 °C and 100 °C
- Intake air temperature between 10 °C and 100 °C

Standard fault codes in accordance with ISO 15031
Diagnostic fault codes, which can be issued by the control module, are standardised in accordance with ISO 15031. This ISO standard is based on SAE/ 2012.

The fault code (DTC = Diagnostic Trouble Code) is always a 5-character alphanumeric value, e.g. "P0100".

The first character of the code (a letter) identifies the system that set the code. In all, there are four system types:
- P for Powertrain (all OBD2 fault codes begin with this)
- C for Chassis
- B for Body
- U for future systems.

The P codes for powertrain are divided into two main categories in accordance with ISO 15031:
- Uniformly standardised codes: P0XXX and P2XXX; these are the same for all manufacturers
- Manufacturer codes: P1XXX and P3XXX; only the first three characters are standardised here (example: P13XX for ignition system diagnosis or misfire detection); the last two digits can be selected freely by the manufacturer.

Only the P codes are required for OBD II.

The standardised codes are subdivided as follows:
P0001 to P0299 Fuel and air proportioning
P03xx Ignition system and misfire detection
P04xx Additional exhaust regulations
P05xx Speed and idle speed control
P06xx Computer and output signals
P0700 to P0999 Transmission

P2000 to P2299 Fuel and air proportioning
P23XX Ignition system and misfire detection
P24XX Additional exhaust regulations
P25XX Additional input signals
P26XX Computer and output signals
P27XX Transmission
P28XX Reserved
P29XX Fuel and air proportioning

Definition of terms

Warm-up cycle
Warm-up cycle means the warm-up phase of the engine. To satisfy the 'warm-up cycle' condition, the engine temperature must not exceed a certain value during starting (presently 44 °C). The operating phase of the engine must last long enough to achieve a certain temperature increase (presently 21 °K, although the temperature reached must be at least 54 °C). The warm-up cycle condition is required in order to decrement the deletion counter for faults that are registered as "remedied" (on this see the paragraph 'Remedying faults').

Driving cycle
A driving cycle consists of the engine start, an arbitrary journey (with idling, part load, constant-speed driving and trailing throttle phase components) and the time after switching off the engine until a new start. For faults to be frozen/remedied, the driving cycle must also partly include the procedure of the respective diagnosis.

Ready status
The menu item "Ready status" displays whether the required fault checks of the OBD system have been performed since the last 'Clear fault memory' or 'Reset'. If a check is OK, testing for a Ready status once is sufficient; if the system is faulty, the Ready status is reached after testing twice.

The Ready status is important for example when testing the exhaust; it detects if the fault memory has been cleared before testing a faulty vehicle without remedying the cause(s) for the fault entry.

The Ready status is displayed for the following subsystems:
- Catalytic conversion
- Tank ventilation system
- Secondary air system
- Oxygen sensor
- Oxygen sensor heating

Once a subsystem has attained the Ready status, this is maintained until the next 'Clear fault memory'.

NOTE:
- In some countries (currently USA, Canada), after intervention on the DME, it is necessary to reset the Ready status before delivering the vehicle to the customer.
- To do this, perform the short tests recommended in the 9588 Porsche System Tester II or a test drive to obtain the relevant diagnostic conditions (these can be found for each system at the beginning of the instructions for finding P codes).
- Please refer any questions on this to your importer.

Freeze frames ('frozen fault boundary conditions' specified by the authorities)
Freeze frame data is standardised and records operating conditions in the event of a (first) fault. Freeze frames have different priorities.

This may be important in the case of output to a scan tool, as there may be only one freeze frame that can be displayed, although several faults are stored (misfires or fuel supply faults override the freeze frames of other faults).

Freeze frames can, for example, be examined in the "extended fault memory" of the 9588 Porsche System Tester II.

The control module must be able to output the following freeze frame data to a standard diagnostic unit (scan tool):
- Fault codes causing this freeze frame to be stored
- Engine load
- Engine speed
- Coolant temperature
- Oxygen control status (open or closed loop)
- Mixture adaptation values
- Fuel pressure (if available - not the case for DME 7.8)
- Intake pipe pressure (if available - in the case of DME 7.8 for turbo vehicles only)
- Vehicle speed

In the case of DME 7.8, a freeze frame is stored for each initial occurrence of a fault that contains all the actual values referred to above with the exception of fuel pressure.

Further environmental conditions
In addition with DME 7.8, for every occurrence of a fault, three further operating conditions (actual values at time of fault occurrence) as well as operating hours and total mileage since model year 2002 are also stored. There is a memory entry for the first occurrence of the fault (remains stored) and a further entry for each last occurrence of the fault (updated for each new occurrence). This data can provide reference points to the cause of the fault in difficult diagnoses and can only be viewed in the "extended fault memory" of the 9588 Porsche System Tester II. The list of possible environmental conditions partly covers more than one freeze frame so that important environmental conditions can also be stored after the first fault occurrence.

Fault persistence (confirmation of a suspected fault)
When a fault occurs for the first time during a diagnostic routine, it is stored as a suspected fault. At the same time a fault persistence counter is started with a certain value (e.g. 2). In the course of further diagnostic operations, if the fault is present in the same range window the counter is decremented by 1. If the persistence counter has the value 0, the fault is assessed as persistent and registered accordingly. If provided for by the fault category, the CE lamp is also activated.

Remedying faults (CE lamp OUT)
When a fault occurs for the first time during a diagnostic routine, it is stored as a suspected fault. In the subsequent driving cycle, the suspicion is either confirmed (fault recurs) or cancelled (fault does not recur, no indication on a scan tool). If the fault activates the CE lamp, a fault correction counter is started at the same time with a certain value (e.g. 5). In the course of further diagnostic routines, if the fault is not present in the same range window the correction counter is decremented by 1. If the correction counter has the value 0, the fault is assessed as remedied. If the fault activated the Check Engine warning light, this will be switched off if not prevented by any further fault. The fault remains in the fault memory for the time being and is only deleted after a number of further warm-up cycles (defined in the fault deletion counter) (workshop assistance if for example the tank cap is temporarily not correctly screwed in).

Fault deletion counter
A separate deletion counter is run for every fault detected. It contains the specified number of GO checks until deletion of the corresponding fault from the fault memory.

When a fault is first detected, the deletion counter is, for example, set to 80 (suspected fault).

If a non-persistent fault is detected as remedied, the deletion counter (only visible for the PST2) is set to 10 (workshop assistance if fault very sporadic).

Whenever a persistent fault is detected (= CE lamp ON), the deletion counter is set to 40, for example. This value is retained until the fault is detected as having been remedied.

The deletion counter is decremented by 1 after every warm-up cycle if the fault is non-persistent fault or detected as remedied. Confirmed faults not detected as remedied are not decremented in the deletion counter. If the deletion counter reaches the value 0, the fault is deleted from the memory.

Fault frequency counter
This counter shows how often a fault has recurred since its first occurrence. If the frequency value is 1, the fault has only occurred once. It can now be either "present" or "not present". Every time the fault status changes from "not present" to "present", the number in the frequency counter is increased by 1. A rather high value in the fault frequency counter may therefore indicate a loose contact. It should be noted that the environmental conditions apply only to the first and the last occurrence of each fault.

Warning notes

DANGER:
- Danger of accident when operating test and diagnostic equipment (PST2, scan tool etc.) while the vehicle is in motion.
- While the vehicle is in motion always get a second person to operate test and diagnostic equipment
- This also applies to the "smaller valve lift" system check for the 'VarioCam Plus' adjustment
- Many tests or system checks can impair the drivability of the vehicle, so only perform these in areas closed to road traffic.
- Gasoline is toxic.
- Inhaling vapours can lead to irritation of the mucous membranes and eyes
- It represents a serious risk to health when inhaled, touched or swallowed over longer periods
- Wear a breathing mask with active charcoal filter; do not breathe in any fuel vapours
- Wear protective gloves that are fuel-resistant
- Only work on the fuel system in well-ventilated spaces
- Before opening the fuel lines or fuel hoses, relieve the fuel pressure
- Collect escaping fuel, absorb it if necessary with a suitable binding material and dispose of properly (special-category waste.)
- Pay attention to cleanliness when working on the fuel system
- Danger of fire and explosion when handling gasoline
- Keep clear of ignition sources
- Do not smoke
- Danger of fire due to naked flame and flying sparks, e.g. during welding or grinding work
- Danger of fire due to escaping fuel (e.g. on hot engine components) and/or electrostatic charge
- Make the vehicle safe, e.g. with a warning sign
- Change any clothing soaked with fuel immediately
- In case of fire, use CO2 or dry powder fire extinguishers

WARNING:
- Risk of injury due to hot and/or rotating parts.
- Never work on the engine when it is running or hot or on a hot exhaust system.
- Danger of injury due to rotating fan. Fans can suddenly start if the air conditioning system is switched on or the engine compartment is hot. Never work in this area if the engine is running.

CAUTION:
Danger of damage due to improper handling of batteries and control module plug connections.
- Never disconnect battery with engine running.
- Never start engine if battery terminal clamps are not connected securely.
- Never pull off or push on plug connections for the control modules or other electronic components when the ignition is switched on.
- Observe the warnings in the body manual before carrying out welding on vehicles.