DME 7.8
DME 7.8
INTRODUCTION
General
The target group of this manual 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".
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 manual describes 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 J 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
P0700to 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 in).
- 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. See also the next section.
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.
Notes on troubleshooting
Working on the oxygen sensors
NOTE: Oxygen sensors used with the DME 7.8
The LSU (Lambda sensor Universal) is able to determine the lambda value in a wide range window
The LSF (Lambda sensor Flat) is only able to determine lambdas greater or less than 1 (the rich/lean jump)
Arrangement of oxygen sensors for 996 Turbo
Arrangement of oxygen sensors for 996 aspirated engine
1 - Oxygen sensor in front of catalytic converter
2 - Oxygen sensor after catalytic converter
NOTE:
- Do not interchange oxygen sensors before and after the catalytic converter, otherwise implausible error entries will arise. This information refers to the possibility of installing a sensor before the cat in the installation position of a sensor after the cat in the exhaust line. The plugs themselves are coded and cannot be interchanged.
- Do not use contact spray on the plug connections of the oxygen sensor, otherwise irreparable damage will be caused to the lines (contamination of the oxygen sensor via the reference air duct).
Troubleshooting procedure
Troubleshooting can only be performed when the fault is present. In other words, specific troubleshooting can only be performed in accordance with instructions (given under Diagnosis/troubleshooting for each fault code) if the entry has the status 'present' in the fault memory.
If the fault is currently 'not present', please check the following:
- Is the fault correction counter and perhaps the deletion counter decremented? This would provide information on a remedied fault (however achieved)
- Is the fault an old one? Read out the extended fault memory (operating time and mileage at last fault entry)
- Are the diagnostic conditions satisfied? If necessary, perform a short test or test drive
- Are officially approved plug connections and ground points of the affected current path OK?
- Set all wiring harnesses of the affected current path to a state that corresponds to driving by pulling and shaking them (loose contact)
- Condition/gas tightness of catalytic converter
- For the tank system: Condition/gas tightness of hoses and the tank cap, if applicable
Diagnostic conditions
NOTE:
- Important: All unnecessary electrical loads must be switched off before the diagnosis. When working on the vehicle with the ignition switched on for fairly long periods (above approx. 15 minutes), a suitable battery charging unit must be connected.
- The control module can only detect the fault if the requirements listed under 'Diagnostic conditions' are met. For this reason, the specified procedure must be observed after a fault is repaired:
1. Clear the fault memory after printing out or saving
2. Satisfy the requirements listed under 'Diagnostic conditions' or perform a short test with the 9588 Porsche System Tester II. It should be noted here that, owing to reset adaptation values (in particular for fuel supply and misfire detection), fault detection by the DME control module is only possible after a fairly long driving time. If may be necessary to observe the relevant adaptation values ("actual values") during a subsequent test drive to be able to identify any trend
3. Read out fault memory again.
Possible causes of fault
NOTE: The 'possible causes of fault' that are responsible for the fault are listed here. Please note that in certain circumstances further faults may be stored in the fault memory after troubleshooting (e.g. if plugs are disconnected). After repairs, read out the fault memory of all control units and delete the faults appearing as a result of the troubleshooting and repairs.
DME faults
NOTE:
- A faulty control module is extremely rare. Although in theory almost any fault can also be caused by a faulty control module, it has been shown in the past that, particularly in the case of DME control modules, even control modules sent in for checking were OK.
- At this point we again stress that before exchanging a DME control module (the final logical step at the end of unsuccessful troubleshooting), all other possible fault causes must be rigorously checked; if necessary, delete the fault entry and perform a test drive or short test.
- If other faults are entered, then remedy these first as instructed (An example: a fault in adjusting the inlet camshaft may under certain circumstances also lead to an oxygen sensor fault being output).
- Fault entries solely in connection with the troubleshooting, repair or programming of control units (e.g. CAN timeout faults) should be deleted.
Diagnosis/troubleshooting
NOTE: The fault memory Info key F8 on 9588 Porsche System Tester II can be used to access the 'extended fault memory'. Besides the freeze frames and environmental conditions, this also includes information on the fault type
Fault type
The following fault types are possible for the DME
- Above upper limit (Max)
- Below lower limit (Min)
- No signal/no communication (Sig)
- Signal implausible (Plaus)
Several fault types may be stored at the same time.
Fault status
The following status types are possible:
- present
- not present
This information should be saved using the Save key F4 and printed out.
NOTE:
- Faults "not present": Where faults are entered but not actually present, after obtaining or adjusting the diagnostic conditions, wiring positions connected to moving parts on and in the vehicle must be checked systematically. Various statuses that can cause a fault to occur must be simulated with the aid of the wiring diagram. It should be noted that the 9588 Porsche System Tester II shows the current fault status only conditionally. The fault frequency counter gives information on operating time and mileage at last fault occurrence
- In difficult cases where faults are currently not present, it is recommended to clear the fault memory (after printing out) and to observe whether the fault is re-entered whilst simulating a loose contact.
- Visual inspection of plug connections: As part of troubleshooting, it must be ensured that the pins of affected plug connections, both on the wiring side and component side, are neither damaged nor corroded. Furthermore, the wiring and plugs must be checked for external damage (cracks, etc.) and proper contact (pins not bent, spread or pushed into the housing). Repair damaged or corroded pins if possible, otherwise replace them. Repair or replace damaged wires. If wiring to the oxygen sensors is damaged, always replace the complete sensor.
- Visual inspection of components: As part of troubleshooting, it must be ensured that there are no signs of visible damage (e.g. cracks, deformation or chafed areas) on the affected components and wiring harnesses. This is particularly important for components that cannot be tested with a multimeter, e.g. bar ignition modules, or components that can cause sporadic faults due to penetrating moisture.
- Battery voltage and signals: A battery voltage of between 11.4 and 14.5 V is generally required for diagnosis/troubleshooting. This must be checked and, if necessary, guaranteed by means of a battery charging unit.
- Specified resistance values are based on an ambient temperature of 20 °C unless otherwise stated.
End of troubleshooting (-> End)
-> End marks the end of the described diagnosis/troubleshooting in the troubleshooting tables. After successful repair, the fault memory of the DME control module must be cleared and, if necessary, adaptation of the throttle adjustment unit performed, followed by a short test or test drive to achieve the diagnostic conditions for the particular fault. Afterwards the fault memory must be read out again. Depending on the country, Ready statuses must be generated.