LEARNING GUIDE POWERTRAIN SPECIALIST VOLKSWAGEN POWERTRAIN CONTROL SYSTEMS DIAGNOSTICS TWO COURSE NUMBER: PT310-02
Notice Due to the wide range of vehicles makes and models, the information given during the class will be general in nature and should not be taken as specific to any vehicle/unit. Please consult manufacturer specifications for the correct number/specifications and repair procedures for the vehicle you are testing. This document is meant to be used as a guideline only. For further information, please contact: 1888 224 3834 No part of this book may be reproduced, stored in any retrieval system or transmitted in any form or by any means (including but not limited to electronic, mechanical, photocopying and recording) without prior written permission of CARS Network. This applies to all text, illustrations, tables and charts. Copyright 2010 CARS Network Page ii
Introduction OBJECTIVES Upon successful completion of this segment the participant will be able to: Interpret scan tool data from various input and output devices and understand the direct relationship to powertrain management and control. Locate and identify system components related to fault detection DTCs Describe the function, normal operation and symptoms of failure regarding system components. Perform diagnostic test procedures Expanded information and diagnostic s concerning: - Injector Circuit Malfunction P0200-P0212 - Injector Short to (B+) or Ground P0261-P0296 - Accelerator Position and Angle P0220-P0229 - Control Module (ECM) Malfunction P0600-P0619 Page 1
Volkswagen Powertrain Control Systems: Module Two In this module, we will focus on fuel injection systems and Powertrain diagnostics, specifically idle control, fuel systems and accelerator controls. Remember to always consult service information before diagnosing any vehicle s control systems. Idle Control Auxiliary Air Valve (All CIS and Digijet Systems) The auxiliary air valve provides a stable idle RPM during cold engine temperatures. During cold engine temperatures the auxiliary air valve will route air around the throttle plates to attain the higher RPM. An electrical coil is incorporated within the auxiliary air valve. After a predetermined amount of run time, the electrical coil will slowly close the passageways in the auxiliary air valve. Idle Air Stabilizer Valve (CIS-E, CIS-E Motronics, All Digifant, Motronics 2.9 & 5.9 Systems) An electronically operated idle stabilizing valve controls air flowing through the idle bypass channel. The ECU/ECM controls the duty cycle of the ISV. The ECU will rely heavily upon the idle switch and coolant temperature sensor to accurately control idle speed. Note: With the key on, throttle closed and the coolant temperature sensor connected there should usually be a humming sound coming from the ISV consult service information for details. Page 2
Idle Speed Boost Valve (Most CIS-E, CIS-E Motronics, All Digifant, Motronics 2.9 & 5.9 Systems) Digijet Systems: An electronically operated idle stabilizing valve (ISV) controls air flowing through the idle bypass channel. A separate idle stabilizer controller controls the idle stabilizing valve. Mono-Motronics: The Mono-Motronics ECM electronically controls the idle speed through the throttle position actuator. The throttle position actuator acts directly on the throttle plate to maintain idle control. Cold Start Valve (All CIS and Digijet Systems) In order to provide the additional fuel requirements during cold engine starting, the CIS system uses a separate cold start injector. A Thermo-Time Switch controls the voltage to the cold start valve depending upon engine temperature Injector Nozzles (All CIS Systems) The CIS system utilizes the use of poppet style fuel injectors. The injectors will begin to open at a predetermined pressure and as airflow increases so does the fuel pressure to the Pin Spring Filter injectors. As fuel pressure increases to the injectors so does the fuel quantity. O Ring Fuel Line Connection Common problems: Injector seals leak common site for vacuum leaks Injector spray pattern may also cause problems Page 3
Fuel Injectors (All Electronic Systems) The fuel injectors are electrically operated solenoid valves which are connected to a common fuel rail. The fuel injectors are supplied with 12 volts and the ECM/ECU completes the ground circuit. The longer the on-time the more fuel will be delivered to the engine. The Digijet and Digifant systems fire the fuel injectors in groups where as the Motronics systems fire the fuel injectors sequentially. The Mono-Motronics system only has one fuel injector. Fuel Pump (All CIS Systems) Most Volkswagen applications will incorporate two electric fuel pumps. The main fuel pump is located on the vehicles crossmember while the auxiliary or transfer pump is located in the fuel tank. The main fuel pump creates the system operating pressure of 68-80psi, while the transfer pump simply draws fuel from the tank to supply the main fuel pump with fuel. Both electric fuel pumps are activated by the fuel pump relay. The vehicle RPM signal activates the fuel pump relay. To maintain fuel residual pressure you will find one or more check valves in the fuel system. This will prevent the fuel system having to be primed with each starting event. Fuel Pump (All Electronic Systems) The fuel pump assembly is located in the fuel tank. An inlet filter helps to prevent fuel pump damage. To prevent high pressure from damaging the fuel system an integral pressure bypass valve has been incorporated within the fuel pump assembly. In order to retain residual fuel line pressure a check valve is installed at the fuel pump outlet. Operated fuel line pressures vary depending upon the application. Page 4
Battery disconnecting/reconnecting (1998-2005 Passat) always consult service information: Lead-acid batteries Negative then positive Obtain radio code Ignition off, key removed before disconnecting battery Electronic Control Unit (ECU) Early example: CIS-E Systems The electronic control unit constantly attempted to correct the air/fuel mixture based mainly upon the output signal from the oxygen sensor. The ECU would send a varying signal to the pressure differential regulator. The ECU also controlled the idle air stabilizer valve. Newer Systems (1999-2005) ECM may control many systems, not just fuel systems (throttle, cruise, etc.) ALWAYS consult service information May use CAN data to communicate Usually need the dealer scan tool if replacing the ECM Preliminary diagnostic checks: Fuses Connectors Battery voltage Typical ECM location for newer Jetta, under windshield area ALWAYS consult service information Page 5
Replacement Cautions: Check the control module identification of the old module before removing the module Check that the replacement ECM control module identification matches the new control module identification May need VW scan tool for relearn (functions such as cruise control may not be written using the generic scan tool) always consult service information Theft deterrent may need to be reset using scan tool May need to generate readiness code after replacement consult service information Note: P0600 may be a CAN problem Checking terminal resistance ALWAYS consult service information ECM communicates with all modules on the data bus using CAN (Hi and Low) missing information is recognized as a malfunction and stored. CAN-Bus needs terminal resistance to operate correctly This central terminal resistor is located in the ECM Resistance specifications: 60-72Ω, pins 58 and 60 (ALWAYS consult service information) Engine RPM Sensors Early Example: CIS Systems The engine RPM sensor is located in the engines ignition distributor. Hall effect type produces a digital signal as the distributor shutter blades rotate past the air gap of the Hall effect sender. The ECU will use this signal for fuel and idle control. Page 6
Digijet, Digifant II & I Digijet system: the RPM signal is received from the ignition control unit, which in turn receives a signal from the hall switch (or sender) within the ignition distributor. The ECU will use this information to tailor the fuel curve. Digifant systems: the signal is derived from the hall switch or sender within the ignition distributor. The ECU will use this information to tailor the fuel and ignition curve. Motronics Systems The crankshaft speed and piston position information is provided by the camshaft position sensor (CMP) on the Mono-Motronics systems. This is a hall effect switch located in the ignition distributor. On the Motronics 2.9 and 5.9 the engine RPM signal is derived from the crankshaft speed sensor. The sensor is located on the cylinder block and reads a 58 tooth plus a 2-tooth gap wheel on the end of the crankshaft. If the two-wire variable reluctance sensor fails, the engine will not start. The camshaft sensor (Hall) sensor on the Motronics systems identifies cylinder position for knock regulation and sequential fuel injection control. On the four-cylinder engine, the camshaft position sensor is located in the ignition distributor and the six cylinders is located in the cylinder head. Typical service specifications for RPM sensor (ALWAYS consult service information): AEG engine: 480-1000Ω, AVH, AZG, BBW, BEV engines: 730-1000Ω (1999-2005 Jetta used in example) Page 7
Oxygen Sensors Critical emission sensor Always diagnose DTCs correctly oxygen sensor DTCs may be set by other systems Newer (WRAF) sensors may be expensive to replace and may need to generate readiness code before releasing the vehicle Switching style sensor: Zirconium dioxide Generates its own voltage Measures exhaust oxygen content only Use correct adapters when diagnosis never jam a test light or probe into the connector or terminal Some instructors use T pins from craft stores with good results Operates in similar way to non-vw switching oxygen sensors WHT WHT GRY BLK BLK BRN RED/WHT YEL WHT BRN/WHT RED/WHT BLK/YEL WHT/RED BLK HEATED OXYGEN SENSOR (HO2S) WHT WHT GRY BLK HEATED OXYGEN SENSOR (HO2S) 1996 Jetta typical oxygen sensor schematics Page 8
Wide Band WRAFs The wide band 02 sensor has the ability to measure air fuel ratio over a wider range. The ECM can more accurately meter the fuel reducing emission and better fuel economy. The wide band operates at approximately 650C or 1200F The wide band changes current output in relation to the amount of oxygen in the exhaust stream Exhaust Sample Pump Circuit Reference Voltage Heater Control Example of WRAF operation Heated Oxygen Sensor ECM Pump Current Input Pump Current Low Reference Ignition Relay Fuse Reference Voltage Heater Control Example of WRAF circuit operation Page 9
Additional Diagnostic Information: Secondary Air Injection (AIR) (Motronics Systems): The Motronics ECM controls the operation of an electric air pump which injects fresh air behind the exhaust valves during cold engine operation, reducing hydrocarbon emissions. Vehicle Speed Sensor (Motronics Systems): Not all Volkswagens use an electronic vehicle speed sensor. The vehicle speed sensor (VSS) is a three-wire sensor or Hall-type sensor. The VSS will have small influence on the fuel curve, ignition curve and engine emission components but its main purpose is for electronic transmission and instrument panel control. Air Conditioning Input (Motronics Systems): A signal is sent to the ECU/ECM when the air conditioning is turned on. The ECU/ECM will react by increasing the duty cycle of the idle air control valve and adjust the fuel curve. Automatic Transmission Control Module (Motronics Systems): Shares such information as vehicle speed, gear selector position and kick-down switch with the ECM/ECU. The ECM/ECU tailors the idle speed, fuel curve and ignition timing based upon this information. Battery Input (Motronics Systems): The ECU/ECM will monitor battery voltage and in turn will tailor the idle speed, fuel curve and ignition timing based upon this information. Data Link Connector (Motronics Systems): The ECU/ECM will monitor the current status of the data-link connector and when it is jumped it will flash the check engine light and/or the installed light emitting diode (LED). The flashing light(s) representing a possible diagnostic trouble code (DTC). Page 10
Power Supply Components (Motronics Systems): The Motronics engine management system relies upon power supply relay, fuel pump relay and oxygen sensor heater relay for proper operation. The ECM supplies a ground path for all three relays. The power supply relay will provide power to the ECM as well as many other engine management components. The fuel pump relay supplies power to the fuel pump once the engine is running. The oxygen sensor heater relay supplies 12 volts to the oxygen sensor heater element. Instrument Cluster (Motronics Systems): The Motronics ECM will feed such information as vehicle speed, engine RPM, and engine temperature to the vehicles instrument cluster. Automatic Transmission Controls (Motronics Systems): To compliment the electronic function of the automatic transmissions controls, the Motronics ECM will feed such information as vehicle speed, engine RPM, and engine temperature to the automatic transmission control module. Data Link Connector (Motronics Systems): Once the Motronics ECM is placed in the diagnostic mode, the ECM will begin to flash any diagnostic trouble codes through the installed tester. NOTES: Page 11