Final Control Diagnosis - Audi A8 1994 Service Manual

Motronic injection and ignition system (6-cylinder) - Edition 02.1999
P1648 18056 Data bus drive defective
P1649 18057 Data bus drive
No message from ABS CU
P1650 18058 Data bus drive
No message from dash panel insert
P1853 18261 Data bus drive
Implausible message from ABS CU

3 - Final control diagnosis

3.1 - Final control diagnosis
Notes:
◆ The final control diagnosis can only be performed with the ignition switched on and the engine not running.
◆ The final control diagnosis is terminated if the engine is started or if an engine speed pulse is detected.
◆ During the final control diagnosis, each control element is activated for about 1 minute unless the test pro‐
gramme is deliberately advanced to the next control element by pressing the ⇒ key.
◆ The control elements can be tested either by listening or by touching.
◆ If the final control diagnosis is to be repeated, the engine must be started. (The engine control unit needs
to detect an engine speed of more than 300 rpm.)
◆ The electric fuel pump runs continuously throughout the final control diagnosis.
The final control diagnosis activates the following components in the stated sequence:
1. Solenoid valve 1 for activated charcoal filter -N80
(fuel tank breather valve)
2. Secondary air inlet valve -N112
(only on vehicles with secondary air system)
3. Relay for secondary air pump -J299
(only on vehicles with secondary air system)
4. Intake manifold change-over valve -N156
5. Camshaft timing control 1 (camshaft adjustment valves 1 and 2,
-N205 and -N208)
Test requirements
• Fuses for engine electronics okay
• Fuel pump relay okay
- Connect vehicle diagnostic, testing and information system VAS 5051 (or fault reader V.A.G 1551) and
select engine electronics control unit by entering address word "01" ( => Page
When doing this the ignition must be switched on.
-> Indicated on display:
Rapid data transfer
Select function XX
- Press keys 0 and 3 for the function "Final control diagnosis".
-> Indicated on display:
Rapid data transfer
03-Final control diagnosis
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permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
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Audi A8 1994 ➤
Test CAN data bus =>Page
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2 .)
2.2 - Fault table
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