Coolant Temperature Sensor, Checking

The following procedure applies to vehicles built after 10-90 starting with control units:

49 states: 8A0 907 404

California: 893 901 404

For vehicles built before 9-90 check the speedometer signal by performing electrical test steps 8 and 23 in Repair Group D2.
Requirements
- engine cold





- connect VAG 1551 Diagnostic Tester using VAG 1551/1 adaptor wire as follows:
- first connect black connector from VAG 1551/1 to black diagnostic connector 1
- after "VAG SELF-DIAGNOSIS" display appears, connect white connector from VAG 1551/1 to brown and/or white diagnostic connector 2

If display does not appear; do not connect white connector

- check voltage supply to VAG 1551 using wiring diagram

- start engine and let idle
- press 1 button to enter "rapid data transfer"
- press 0 and 1 for address word "engine electronics"
- press Q button to enter input
- press -> button
- press 0 and 8 buttons to obtain "Read measurement block" function
- press Q button to enter input
- display will appear as shown

Read measurement block HELP
Input display group number XX

- press 0 button twice to select display group 00
- display will appear as shown

Read measurement block Q
Input display group number 00

- press Q to enter input
- display shows channels 1 through 10

Read measurement block -->
1 2 3 4 5 6 7 8 9 10

- observe value in channel 1
- - value must drop uniformly and without interruption

If YES

- press -> button
- press 0 and 6 buttons to enter 06 function "end output"
- press 0 button to enter input

If channel 1 display does not drop uniformly (without interruption)

- replace coolant temperature sensor (G 62) and/or CIS-E Motronic control unit (J 204)
- read and then erase Fault memory