From October 1990
Diagnosis, Fault Memory - PassatOutput check diagnosis
Requirements
- fuses 15 and 21 OK
- idle switch OK (closed)
- ground wire connections OK (at intake manifold and battery)
- ignition switched OFF
Note: The following components (in the sequence given) can be checked using this procedure.
1 - Differential pressure regulator (N 73)
2 - Carbon canister frequency valve (N 80)
3 - Idle stabilizer valve (N 71)
4 - Cold-start valve (N 17)
After connecting the VAG 1551 tester, the display alternates between the following operating modes:
1 - Rapid Data Transfer
2 - Blink Code Output
- switch multimeter US 1119 (or equivalent) to Amps range
- connect multimeter to differential pressure regulator using VAG 1315A/1 test adaptor
- switch ON ignition
- display must appear positive, if not, reverse meter leads
[ Rapid data transfer HELP ]
[ Insert address word XX ]
- press button 1 to select operating mode "Rapid data transfer"
- display will appear as shown
[ Rapid data transfer Q ]
[ 01 - Engine electronics ]
- press buttons 0 and 1 to select "Engine Electronics"
- display will appear as shown
- press Q button to enter input
[ Rapid data transfer ]
[ Tester sends address word 01 ]
- display will come on briefly to indicate it has sent the address word 01 (check control unit versions)
[ 8AO907404 MOTOR -> ]
[ Coding 00 ]
- then the engine control unit will respond with an identification display which shows the part number, what system it controls, and when it was coded. (as shown in example)
If display appears as shown instead:
[ Rapid data transfer HELP ]
[ Control unit does not answer! ]
- press HELP key to print out a list of possible failures - after eliminating causes of failure
- repeat all inputs from the beginning to obtain the engine control unit identification screen...then proceed
[ Rapid data transfer HELP ]
[ Select Function XX ]
- press -> button
- display will appear as shown
[ Rapid data transfer Q ]
[ 03 - output check diagnosis ]
- press "0" and "3" buttons to select Function 03: "output check diagnosis"
- display will appear as shown
[ Output check diagnosis -> ]
[ Differential pressure regulator (N 73) ]
- press Q button to enter input
- display will appear as shown
- observe control current on multimeter
- control current must fluctuate from 0 to 100 mA
If NO
- check wiring using wiring diagram
- check differential pressure regulator resistance
If wiring and resistance measurement OK
- replace CIS-E Motronic control unit (J 204)
[ Output check diagnosis -> ]
[ Carbon canister frequency valve (N 80) ]
- press -> button
- display will appear as shown
- frequency valve must click
If valve does not click
- check control as follows
- remove harness connector from frequency valve
- connect LED tester US 1115 (VAG 1527B) to harness connector using VW 1594 adaptor kit
- LED must flash
If LED flashes
- replace frequency valve (N 80)
If LED does NOT flash
- check wiring
If wiring OK
- replace CIS-E Motronic control unit (J 204)
[ Output check diagnosis -> ]
[ Idle stabilizer valve (N 71) ]
- press -> button
- display will appear as shown
- idle stabilizer valve must click
If NO
- check control as follows
- switch OFF ignition
- disconnect idle stabilizer valve harness connector
- connect valve to harness connector using adaptor wires VW 1594/1, /2 and /19
- connect LED tester to adaptor wire VW 1594/19 using adaptor VW 1594/15
- repeat output check diagnosis from the beginning
When display: "Idle stabilizer valve (N 71)" has been obtained
- LED must flash
If LED flashes
- replace idle stabilizer valve
If LED does NOT flash
- switch multimeter US 1119 (or equivalent) to resistance range
- measure idle stabilizer valve resistance
- must be 4 to 12 Ohms
- check wiring
If wiring OK
- replace CIS-E Motronic control unit (J 204)
[ Output check diagnosis -> ]
[ Cold-start valve (N 17) ]
- press -> button
- display will appear as shown
- open throttle slightly
- cold-start valve must click
Note: The valve only is activated ten times to avoid "flooding" the engine. To repeat this check, the output check diagnosis must be repeated from the beginning.
If the valve does not click, check control as follows
- disconnect cold-start valve harness connector
- connect LED tester to harness connector using adaptor kit VW 1594
- perform output check diagnosis again from the beginning
When display "cold-start valve (N 17)" is obtained
- open throttle valve slightly
- LED must flash ten times
If LED flashes
- replace cold-start valve
If LED does NOT flash
- check wiring
If wiring OK
- replace CIS-E Motronic control unit (J 204)
- press the -> key to continue
- select Function 06 to End Output, and press the Q key to enter that selection