A/C System Signal To Engine Control Module, Checking
The A/C system signal make sure that the engine control module maintains A/C system operation constant regardless of load at idle.
Test Sequence
-- Connect VAG1551/ VAG1552 scan tool VAG 1551/VAG 1552, CONNECTING .
-- Start engine and let idle.
-- Press -0- and -1- buttons to select address word 01: "Engine electronics"
Display will appear as shown (example only):
| 038906018M 1.9l R4 EDC 00AG 1813 → Coding 0001 WSC XXXXX |
-- Press → button.
Display will appear as shown:
| Rapid data transfer HELP Select function XX |
-- Press -0- and -8- buttons to select function 08: "Read measuring value block".
-- Press Q button to enter input.
Display will appear as shown:
| Read measuring value block HELP Input Display group number XXX |
-- Press -0-, -0- and -2- buttons to select "Display group 2".
-- Press Q button to enter input.
Display will appear as shown (1 to 4 = Display zones):
| Read measuring value block 2 → 1 2 3 4 |
-- Switch ON A/C by pressing "Auto" button and selecting lowest temperature.
- A/C compressor must run.
-- Observe display in display zone 3.
If specification not obtained:
-- Connect VAG1598/22 (or 1598/31) test box to ECM wiring harness.
-- Check wiring for open circuit between following test box socket and A/C system using wiring diagram.
Up to MY 1999
Socket 48
From MY 2000
Socket 34
- Wire resistance: 1.5 Ω maximum SYSTEM WIRING Information