With Manufacturer's Scan Tool
A/C signal and engine speed adaptation, checking
This signal provides information to the ECM to maintain a smooth idle even while difficult demands are place upon the engine by the A/C system.
Test sequence
- Connect Scan Tool VAG 1551 (VAG 1552) and select engine electronics control unit with the "Address word" 01. When doing this the engine must be running at idling speed. (Connecting Scan Tool and selecting engine electronics control unit. [1][2][3]Connecting VAG 1551 Scan Tool)
Indicated on display:
Rapid data transfer HELP
Select function XX
- Press buttons -0- and -8- for the function "Read measured value block" and confirm entry with -Q- button.
Indicated on display:
Read measured value block
Enter display group number XXX
- Press buttons -0-, -0- and -2- for "Display group number 2" and confirm entry with -Q- button.
Indicated on display: (1 through 4 Display fields)
Read measured value block 2 ->
1 2 3 4
- Observe display in display field 3, the A/C must not be switched on.
Specification: 0 X 0 (A/C system signal)
Read measured value block 2 ->
1 2 0 1 0 4
- Switch on A/C system. Do this, depending on A/C system installed by pressing switch "AC" on a manually controlled A/C system or pressing switch "Auto" on an automatic (Climatronic) A/C system.
- Select lowest temperature and highest blower speed. The A/C compressor must run.
- Observe display in display field 3.
Specification: X X 1 (A/C system signal)
Read measured value block 2
1 2 1 1 1 4
- Press -> button.
- Press buttons -0- and -6- for the function "End output" and confirm entry with the -Q- button.
- Switch off ignition.
If the specification is not obtained:
- Remove wiper arms and plenum cover.
- Connect test box VAG 1598/31 to control unit wiring harness.
- Check wiring between test box socket 34 and A/C system for open circuit using wiring diagram. Wire resistance: Max. 1.5 Ohm
If no malfunction can be found in wiring:
- Check function of A/C control unit.
- Check DTC memory and, if necessary, repair any malfunctions and then erase. [1][2]Reading Diagnostic Trouble Codes
- Read the readiness code. If the DTC memory has been erased or the Diesel Direct Fuel Injection Engine Control Module - J248- was disconnected from permanent battery positive (B+), the readiness code must be generated again.
Monitors, Trips, Drive Cycles and Readiness Codes
Monitors, Trips, Drive Cycles and Readiness Codes