4/24390, 4/24391, 4/24490
Fault Code 4/24390, 4/24391, 4/24490Malfunction indicated
RPM signal (Td) faulty or absent
Fault symptom
The car goes into Limp Home mode. The TCS CTRL lamp lights up (not fault code 4/24390).
Test procedure
1 Enter ISAT command code 249.
Note: Use the adapter lead with capacitor, part No. 86 11 048, so that the car can be started without having to interrupt communication with ISAT.
ISAT should now display the current engine speed, e.g. 801000 = 1000 rpm.
If it is not, check the OG lead between pin 12 of the connector and pin 29 of the DI/APC control unit for continuity or shorting to earth.
2 Check that the control unit's earth connection on the engine is OK.
3 Carry out fault tracing on the DI/APC system.
4 If no faults are detected, clear the fault code and drive the to see whether it is generated afresh. If it is, try fitting an ETS control unit that is known to be OK.