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Audi Cars 1999-05

General Information


A distributorless ignition system was first introduced on the VR6 equipped Passat models in 1995 and used on all subsequent Passat models equipped with the 2.8L VR6 engine through 1997.

The Audi A4, which was first introduced in 1996, also uses a distributorless ignition system on the 2.8L V6 and on the 1.8L inline 4-cylinder turbocharged engine introduced in 1997.

Beginning with model year 1998, both the Audi A4 and the Passat models share the same 5-valve 2.8L V6 and 5-valve 1.8L inline 4-cylinder engines using distributorless ignition systems.

All vehicles equipped with the 1.8L, 2.8L VR6 and 2.8L V6 engines have distributorless ignition systems that use an Engine Control Module (ECM) to control the ignition timing based on input from a variety of sensors. The ECM has a fault memory, which can store Diagnostic Trouble Codes (DTC's) if a fault is recognized in the ignition system.

The stored faults are categorized as sporadic (intermittent), or present. If the fault is severe enough to compromise the integrity of the catalytic converter or another emissions related component, a warning light such as the Check Engine Light or Malfunction Indicator (MIL) Light is activated.

The most efficient method of diagnosing an ignition related problem on the A4 or Passat distributorless ignition system is to begin by interrogating the ECM's fault memory. This can be done specially designed diagnostic test equipment, such as the VAG 1551 or VAG 1552 diagnostic tester, or its equivalent. This equipment is required for all Audi and VW franchised dealers. Because of their cost many individuals may not invest in this equipment, however an independent repair facility may benefit greatly from the speed at which these or equivalent diagnostic tools operate.

The advantage the diagnostic tools such as the VAG 1551 or VAG 1552 or their equivalent offer is the ability to:

Interrogate the ECM fault memory
Check sensors without probing their wires
Check sensor operational values
Check every sensor used by the ECM
Check sensors without disconnecting them
Check sensors without removing them
Ability to reset the Check Engine Light
Ability to clear and reset the ECM fault memory

In 1996, all passenger vehicles sold in the US had to meet the mandated On Board Diagnostic version two (OBD II) standards. These standards mandate that the fuel and ignition control systems must provide a standardized 16-pin diagnostic electrical port referred to as the Data Link Connector (DLC) that can be accessed by a Scan Tool. The components used by these systems also use standardized nomenclature and the Diagnostic Trouble Codes (DTC's) are formatted such that they can be read and decoded to interpret their meaning. For additional information, please refer to the following topic(s): Driveability and Emission Controls, OBD-II Trouble Codes.

The Distributorless Ignition System does not use a conventional distributor. The system eliminates any moving parts, providing a completely wear-free, solid state ignition system.

The heart of the system on 2.8L V6 and VR6 engines consists of a coil pack comprised of three separate ignition coils, or an individual coil pack for each cylinder, as found on the 1.8L engine. These coils are controlled by the ECM, based on the inputs of the various sensors on the engine.

Systems using a coil pack in their distributorless system produce a 'waste spark' such that the companion cylinders are paired and the spark occurs simultaneously in the cylinder with the piston coming up on the compression stroke and in the companion cylinder with the piston coming up on the exhaust stroke.

The distributorless ignition system is composed of the following components:

Electronic Control Module (ECM) -The ECM is the 'brain' of the ignition system. The ECM controls when the spark occurs based on the input from the various sensors on the engine, including the knock sensor, coolant temperature sensor, crankshaft position sensor, and the Oxygen (O 2 S) Sensor.
Ignition Coil or Coil Pack -On 1.8L engines each cylinder has a separate ignition coil. On V6 and VR6 engines, the ignition coil pack actually consists of three separate double-sided ignition coils. These coils operate in the same manner as a conventional coil.
Knock Sensor -A Knock (KS) Sensor is a peizo-electric device that senses detonation or pre-ignition from the engine block. When the engine begins to knock, the sensor produces a small amount of voltage. This voltage is detected by the ECM, which typically retards the ignition timing slightly to prevent detonation.
Crankshaft Position Sensor -The Crankshaft Position (CKP) Sensor is used by the ECM to monitor the engine's speed, to tirgger the ignition coils and the fuel injectors. On models equipped with a tachometer, this sensor is used as input for the tachometer. The signal is also used by the ECM to recognize when to activate the fuel pump relay. If the engine stops running or reaches an over-rev condition, the ECM shuts off the fuel supply. Typically, the crankshaft position sensor is located on the engine block and is triggered by a cog wheel or by the ring gear teeth on the flywheel or flex plate.
Camshaft Position Sensor -The Camshaft Position (CMP) Sensor provides the ECM with information as to the relative position of each piston in the engine. By informing the ECM as to the sequence and when a piston nears Top Dead Center (TDC) on the compression stroke, The ECM knows exactly when to operate each cylinder's fuel injector and provide the ignition spark. The sensor uses an indicator on the camshaft or camshaft sprocket that informs the ECM when the piston for cylinder No. 1 is reaching TDC on the compression stroke.

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Fig. The 1.8L engines use a separate ignition coil for each cylinder. The coil is installed directly on top of the spark plug

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Fig. The 2.8L V6 engines use a coil pack consisting of 3 ignition coils that have 2 spark plug wire connections per coil