Engine Code 1Z or AHU
Engine Coolant Temerature (ECT) sensor, checkingSpecial tools, testers and auxiliary Items:
VAG1551 or VAG1552 scan tool
VAG1551/3 adaptor cable
VAG1598/18 test box
Multimeter (Fluke 83 or equivalent)
VW1594 connector test kit
Wiring diagram
Test sequence:
Connect VAG1551 or VAG1552 scan tool
Start engine and let idle
Press -0- and -1- buttons to select address word 01 "engine electronics"
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 confirm input
Display will appear as shown:
Read measuring value block HELP
Input display group number XXX
Press -0-, -0- and -7- buttons to select display group no. 7 (007)
Press -Q- button to confirm input
Display will appear as shown:
Read measuring value block 7 ->
15.4°C 15.9°C 16.7°C
Observe ECT value in display zone 4
Value must increase uniformly and without interruption
NOTE: If the ECT sensor malfunctions, the fuel temperature sensor values are substituted to provide a backup.
If an unreasonable value appears in display zone 4 or the fuel temperature has been supplied as a substitute; check the ECT sensor and wiring connections to sensor as follows:
Press -> button
Press -0- and 06- buttons to select "End Output" Function 06.
Press -Q- button to confirm input
Switch ignition off
Disconnect harness connector from ECT sensor -1-
Measure resistance between sensor terminals 1 and 3
Specifications: refer to diagram for resistance values
Scale A: for temperatures 0° - 50°C (32° - 122°F)
Scale B: for temperatures 50° - 100°C (122° - 212°F)
Examples:
30°C (86°F) corresponds to a resistance of 1500 to 2000 Ohms
80°C (176°F) corresponds to a resistance of 275 to 375 Ohms
If resistance is outside the specified range:
Replace engine coolant temperature sensor -G62-
Display readiness code
If DTC memory was erased:
Create readiness code again
If resistance is OK:
Connect VAG1598/18 test box to Diesel DFI ECM connector
Check wiring for open circuit between 4-pin connector and test box, using wiring diagram
Terminal 1 + test box socket 33
Terminal 3 + test box socket 14
Wire resistance: max. 1.5 Ohms maximum
Check wires for short circuit between terminals at 4-pin connector.
Specification: Infinite (no continuity)
If wiring is OK:
Replace Diesel DFI ECM -J248-
Check and erase DTC memory
NOTE: Disconnecting the engine coolant temperature sensor always generates a DTC, which must be erased.