Volkswagen-Audi Vehicle Communication Software Manual [888kb ...

Testing
Testing Engine Systems
4. Road test at Wide Open Throttle (attain at least 3500 RPM).
5. Decelerate.
6. Perform all steps several times.
Remember that all modules should be re-checked for codes after the test drive. Use automatic
test mode to automatically print out all interrogated modules and codes (“00-Automatic
System Test” on page 20).
Important Tips for Codes
• The message on the scan tool states that to clear codes, the engine must be off. Input from
field technicians indicates that this is not always necessary.
• Intermittent codes have the message “Error Occurs Intermittent” after the code description
(VW calls these codes “sporadic”). Codes are considered intermittent if they occur for a
maximum of five seconds. Intermittent codes do not turn the Check Engine Light on. They are
automatically erased from memory after 40 drive cycles if they do not occur again. When a
malfunction is first detected, it is stored as a static or pending malfunction. If the malfunction
no longer exists after a pre-determined time or distance travelled, then it is labelled
intermittent.
• Most 1995 and earlier Bosch control modules may show you a false DTC “00513 - Engine
Speed Sensor (G28)” if the engine is not running. This fault code should disappear once the
engine is started. With a defective sensor, the engine would not start. In addition, many
automatic transmission control modules may show a DTC that indicates a faulty brake light
switch. This usually can be ignored and usually will not appear if you press the brakes once
before checking for fault codes.
• Disconnecting the battery may erase fault codes and basic settings on pre-OBD-II vehicles,
which may result in driveability problems. Disconnecting the battery on OBD-II vehicles does
not erase stored codes or turn the MIL off. However, intermittent codes and control unit
adaptation learned values may be erased in both the engine and transmission.
• Disconnecting the battery may require resetting of convenience electronics such as alarm,
interior lights, radio, etc. It is recommended to use a jumper battery or battery charger to
maintain power when replacing a battery.
• Readiness Codes need to be reset after codes are cleared or the battery has been
disconnected. Throttle body adaptation relearn is essential and may prevent the engine from
starting. See “Testing Electronic Throttle Systems” on page 67 for more information.
• Be aware that clearing codes may not change throttle body adaptation status to “not ready”
(060 or 098), but throttle body reset is highly recommended to ensure no problems. See the
Volkswagen/Audi OBD-II Readiness Code Charts for additional information.
• Sometimes a fault code is displayed for a component which is not installed in the vehicle
under test (i.e., a cruise control). This code cannot be cleared. Always make sure the
component the code refers to is present when a code cannot be cleared.
• Performing activation tests may set false codes. Always check and clear codes after
performing activation tests.
• Vehicles with Drive-by-Wire (no throttle cable) cannot be power-braked. The Brake On signal
notifies the control module to command the throttle closed and may also set false codes.
• Vehicles with full Drive-by-Wire (no throttle cable), usually have a EPC (Electronic Power
Control) indicator light. The EPC light should come on if there is any problem in the
Drive-by-Wire system. Faults detected by the EPC set duplicate fault codes in the ECM.
• Electronic Instrument Clusters may store only up to four fault codes. Intermittent fault codes
are automatically erased if they do not reoccur in the next 50 engine starts.
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