6/78390

Fault Code 6/78390





Note: If fault code 78390 occurs at the same time as fault code 45720, carry out the test procedure for fault code 45240. 4/25240, 4/25242, 4/25250, 4/25252, 4/25290

Malfunction indicated
Throttle butterfly control faulty or absent.

Fault symptom
The car goes into Limp Home mode. The TCS CTRL lamp lights up.

Test procedure

1 First deal with any other fault codes that have been generated at the same time.

2 Check for leaks in the safety valve's vacuum circuit as follows:
^ Start the engine.
^ Disconnect the hose between the non-return valve and the inlemanifold. If this causes the arm on the throttle housing to be retracted, the system has a leak.
^ To pinpoint the leak, pinch the hoses one at a time from the non-return valve via the safety valve to the throttle housing.
^ Change any fault components which could be the cause of the leak.
^ Since it has been found that the non-return valve can leak at a pressure difference of 0-0.1 bar, check the operation of the valve by blowing into it (from the engine side) while the end of a hose connected to the other side is placed in water. If air bubbles occur, the valve is faulty and a new one must be fitted.

3 Create a vacuum in the throttle housing's vacuum chamber to relieve the spring of load. Also disconnect the rubber hose from the throttle housing so that the butterfly can be adjusted by hand.
Check that the butterfly can move freely and does not bind in the throttle housing.




4 With the ignition switched off and the ETS control unit disconnected, check the resistance of the throttle motor by taking readings across sockets 20 and 21 on a BOB.Gradually change the position of the butterfly from closed to fully open. Hold the butterfly still when taking each reading.

Note: Only resistance readings taken when the butterfly is held completely still should be compared with the specified resistance.

At each reading, the resistance should be higher than 1.2 Ohms.
If the resistance is correct, continue with point 6.
If the resistance at any reading is lower than 1.2 ohms, continue with point 5.




5 Unplug the connector from the throttle housing and check the resistance of the motor by taking a reading directly across pins 1 and 7 of the throttle housing socket. Take the readings in the same way as described in point 4.

If the resistance readings obtained according to point 4 were too low and correct readings are obtained according to point 5, check the wiring according to point 6 and remedy any faults.

If the resistance readings are too low according to both point 4 and point 5, try a new throttle housing and check whether the fault code is generated afresh.

6 Check the GN lead between pin 1 of the throttle housing's connector and pin 20 of the ETS control unit's connector for continuity or shorting to earth.
Also check the GN/WH lead between pin 7 of the throttle housing's connector and pin 21 of the ETS control unit's connector for continuity or shorting to earth.

7 If no fault can be found and the above tests check out OK, clear the fault code and drive the car to see whether it is generated afresh. If it is, try fitting an ETS control unit which is known to be OK.