Porsche Meister Technician

the PORSCHE 918 Spyder Plug-In Hybrid - Porsche Intelligent Performance

2010-05-01T11:52:00.000-07:00

Porsche 918 Spyder Concept Promotional Video

2010-05-01T11:49:00.000-07:00

Porsche Carrera GT, Supercar

2010-04-27T18:35:00.000-07:00

Porsche Research & Development Facility

2010-04-27T18:31:00.000-07:00

Renault F1 Engine

2010-04-27T18:30:00.000-07:00

Porsche at the Monterey Historics - Pebble Beach promo 3

2010-04-24T20:32:00.000-07:00

Pancho Villa: El Mayor de los Dorados

2010-04-24T20:30:00.000-07:00

Advanced Diagnostic's

2010-02-02T19:58:00.000-08:00

Circuit-System Testing

There will be 3 basic types of electrical wiring/component faults.
For engine performance faults, you will always have X amount of probable causes. It will be to your advantage to not always use the old age adage that it's usually this that is the problem. It is true that certain vehicles will eventually produce pattern failures, known parts or systems that go bad.

Types of Electrical Problems
• High Resistance Faults
• Low Resistance Faults
• Component Faults
• Intermittent circuit/component failures

Circuit Failure Testing ( Consumer/Function operates intermittently).

If you have a failure that is not always present, intermittent failures can and will be the most difficult to diagnose. If the system is electronically controlled, and its control module is capable of storing a fault code, try to retrieve the fault code with a scan tool. Fault codes will always be a guide to diagnosis and will give you the most probable causes of the fault. There usually is a flow chart tree that will guide you in your diagnosis. There will be times when it is also useful for you to deviate from the test plan and create your own test plan. Think outside of the box.
Remember to that it is vital to gather the following information about any intermittent problem.
• When does the function fail?
• Are any other functions affected?
• Were any other functions in operation at the time of failure?
• Is the failure related to a vibration or bump occurrence?
• Does the failure occur at any specific temperature, time of the day, engine or transmission operating condition?
• Try to recreate the failure by operating the vehicle under the conditions observed at time of problem or described by client.
• If the failure can be replicated, proceed to with general diagnostic tests for the symptoms you observe or feel.
• Warning
• When performing a wire or circuit "wiggle test" make sure that the circuit being tested is not related to the airbag circuits.

Basic Electrical Faults

Basic electrical circuit faults can be categorized as follows:

Open Circuit

An open circuit is a break in the path of current flow. A circuit’s path must be complete from start to end, only then will current flow. An open circuit can be caused by a bad electrical connector or electrical pins with bad crimps, cracked wiring at the crimps, and broken wire strands and faulted components as well. It is essential to understand that if the circuit is powered, it will have voltage potential that will be present in the portion of the circuit that is still connected to the power source. It's also important to know that a bad ground of a circuit or component or connection will increase resistance.

With parallel circuits, an open circuit in one branch of the circuit will stop operation in that branch, but the other branches will continue to operate. An Ohmmeter test can determine if a circuit is open (infinite resistance). Remember that when you are testing for resistance in a circuit to test the integrity of the wiring, you must disconnect the power source and the other end of wire that goes to the component. It all depends on the circuit. As I describe the engine management’s sensor and actuators later in the book, you will see how the wiring tests can be performed.

A voltmeter from a Dvom can also be used to determine an open circuit by measuring the available voltage at various points of the circuit or the voltage drop between two points in the circuit. This procedure also helps to find and determine the location of the open circuit.

High Resistance

A high resistance circuit is a circuit with more resistance than specified. Any circuit resistance should typically in the components that perform work. High resistance will reduce the amount power, current and voltage that should be available to the components connected to the circuit.

High resistance in a circuit can be caused by loose, dirty or corroded connections or internal component failures. Broken strands of wire within the insulation will also increase the circuit’s resistance. When diagnosing a circuit for high resistance, try not to disturb the connections until you have narrowed down the possible area of high resistance. The reason behind this is that you may unintentially clean off corrosion in a connector. This might temporarily correct the fault and make your diagnosis more difficult to isolate.

You can use an ohmmeter to test an unpowered circuit; this will allow you to determine if you have high resistance in the circuit. But the preferred way to test for resistance is using the voltage drop method. We will get into this test method in just a bit.

Low resistance

A short circuit is a low resistance fault that allows too much current to flow to ground due to the low resistance. This will typically blow a fuse or damage wiring or components. Remember that low resistance is always caused by a short to ground or an unwanted ground.

Short circuit to ground

A short circuit to ground occurs when the circuit is grounded or partially grounded where it’s not designed to. Typically with Porsche this is usually caused by radio or accessory installations or body shop wiring repairs or the lack of. If there is a short circuit to ground after the load, the circuit control may be lost, causing operation of components when it is not wanted.

To diagnose a short circuit to ground in a fused circuit, systematically disconnecting circuit components until your voltmeter reads 0 V will identify the area of the short circuit.

Short circuit to power

A short circuit to voltage happens when the insulation fails causing the wire strands to contact the voltage of another circuit. This will cause the circuit or circuits to operate incorrectly. You should carefully observe the symptoms and refer to the appropriate wire diagram to understand the circuit operation flow. Remove fuses until the circuit is isolated, and then measure resistance and voltage to find the problem area.

Component faults

Sensors or Actuators or control units can fail and be faulty even when the part is new. This is definitely the most difficult part of diagnosis, since most of us don’t just have spare parts lying around to plug in and see what happens. But once you have verified that the wiring is ok and that the proper control signals and voltages and grounds to a component are present, then you can start to isolate the failure to a component. I will indicate the proper signals and resistance values and scope patterns that show what a bad and good component look like.

Components can fail from normal wear and tear or an outright defect with the part.

2009-09-05T12:16:00.000-07:00

This is the first part of the Engine Management Basics. I hope that it is interesting and useful information for all of you.

The goal of the fuel system is to maintain the air fuel ratio at the most efficient air to fuel ratio, this is called Stoichiometric. This means that the Air to fuel ratio is 14.7 parts of air to 1 part of fuel. This ratio is called Lambda in German, and is displayed on a Factory style scan tool as either Actual Lambda, Oxygen sensing or Fuel trim mean value. This Lambda value is displayed as 1 and is the equivalent to the Stoichiometric ratio.

Lambda= Air mass (Mass Air Flow) divided by the theoritical required air mass

Lambda less than 1= a lack of air or rich mixture

Lambda greater than 1= an excess of air or lean mixture

When these values are displayed on a scan tool, they indicate the actual air fuel mixture and the health of the engine as well.
It is important to know that if you are using a generic OBD II scanner the Lambda value will not be displayed, but will be shown as short term and long term fuel trim. This will be discussed in detail in later posts though.

Porsche uses a Closed loop Feedback fuel managemet system that has a goal. The DME's ultimate duty is to make sure that emissions do not exceed a certain limit. To do this it needs a variety of sensors and other components that will work in harmony to not only keep emissions under control, but also produce good driveabilty and power at the same time. The engine management system contains map programs that are base starting points and are able to be modified to produce the most optimal performance.

The closed loop feedback systems main input sensors are the Mass air flow sensor and the oxygen sensors before the catalytic converters. The use of the oxygen sensors are essentially informatio sensors that enable the DME to determine if the fuel mixture control is actually doing its job correctly. Think of these sensors like an EKG of the engines overall health. The outputed signals that they produce are extermely useful for engine performance diagnositcs. Diagnosis by analyzing the oxygen sensors will be discussed in the future. For now lets go over how the DME engine control unit determines the amount of fuel that will be needed to in proportion to your accelertor pedal request.

*The DME will look at the mass air flow and the engine speed.
*Then the controller will access its programmed injector duration map.
*Dme determines the injector pulsewidth on-off time for your given engine load and speed range.
*Dme will analyze the oxygen sensor signal inputs and determine the exact fuel mixture that is needed.
*Injector pulsewidth is modified and fine tuned based on the oxygen sensor input

The oxygen sensor is really the heart of the fuel mixture system, without it the DME would not be able to control emissions.
This sensor's signal must stay within a certain range and average, when this is accomplished the catalytic converter will be able to function at its most optimal potential by reducing the gases HC, CO and NOx. The oxygen sensor operates on the galvanic concentration cell principle. Think of this sensor as a battery that can generate voltage. It consists of a ceramic Nernst cell that is made up of ceramic sheets of wafers coated with platinum and are porus as well. When the sensor is at operating temperature of 650*F. thanks to an internal heater, it will react to the exhaust gases concentration of oxygen or lack of it. The sensor has a reference channel to the outside atmosphere which is used for differential measurement. It is important to note that the wiring harness for these sensors should never be repaired as it can affect the flow of air to the reference channel at the top of the sensor.

When there is a difference in oxygen content between the reference air channeled into the sensor and the exhaust stream on the outside of the sensor, then the oxygen ions will migrate from the inside of the sensor to the outside electrodes in the sensor. This creates a voltage in the range of 0.1 millivolts and 0.9 millivolts. This voltage input to the DME is proportional to the air fuel ratio. If the sensor's average is in the range of 450 mv then this is indicative of Lambda 1 and allows for effective control of emissions. Its important to remember that if the internal heater fails or is failing intermittantly, it can effect engine performance and fuel economy. The reason why is that the sensor must stay above 650*F. to be able to generate voltage, if the sensor is not at the right temperature, you can get partial voltage switching that can cause excess lean or rich conditions.

More to come in due time.

Basic Electrical Diagnostic's

2009-06-07T21:39:00.000-07:00

When it comes to engine performance issues such as a check engine light or some body electrical issue, there is always an easy way to troubleshoot and a wasteful way to diagnose. From my personal experience, its always best to not guess but test first. The following are some basic routines that are very helpful and important.

Do you have a complete understanding of how the particular component is supposed to function?
Always use the correct wiring diagram to understand the layout of the system/component.
Verify proper voltage supply to component, control unit or fuses, always check with a Digital volt ohm meter (DVOM).
Inspect all relevant electrical connections, ground points, check for Voltage Drop.
The use of a Scan tool is invaluable to diagnose and test.
Always check for fault codes and reference any technical information available such as Technical service bulletins.
When replacing a part, always use a quality OEM spec part, as some aftermarket components can make new problems or not fix the issue at all.

These are just some basic things but we can get more technical later on specific issues on the various Porsche models later.

2009-06-07T21:15:00.000-07:00

Well this is my first ever Blog post, here it goes. I am fortunate to have the opportunity to work on these awesome cars day in and day out. That being said, I wish I could afford one to take home. Some day I hope.

My passion is everything that has to do with the technical aspects of Porsche's Engine management technology and Body electronics systems. It's so fascinating to see how electronics have taken over the Carrera's. I can only imagine how an owner must feel when his car is not healthy, since I am on the other side of the transactions I'm insulated from the human side of things. I've been recently thinking about writing a book so that an owner can be able to diagnose and repair his 996-997 or 9pa or Boxster. I personally think that if someone can read about how a particular system is designed to work and has the information as to what is normal or not, well if he or she is inclined to take on a little challenge, technical issues can be resolved and repaired.

The new 997 Gen. II is such a technological marvel when it comes to the new engines and DFI system. Some time in the future I'd like to start posting little articles on how the various engine management systems function.