Reading and Clearing Diagnostic Trouble Codes

Fig. 48 Check Engine Light:

The "check engine" light displays as follows:

1. Switch on ignition :
"check engine" light comes on for a system test.

2. Start engine :
a) "check engine" light goes out = no fault in system
b) "check engine" light stays on = fault exists
c) "check engine" light comes on during driving = new fault detected


When the "check engine" light illuminates or stays on during driving, a fault code is stored in the electronic control unit (ECU) memory. This fault code will assist the technician in identifying the defective component. The fault codes can be read by a flashing code emitted by the "check engine" light.

To extract the codes from the ECU, proceed as follows with the engine off:

1. Switch on ignition ("check engine" light comes on).
2. Close full-load contact (in throttle position sensor) by pressing the gas pedal to the full acceleration position for 3-5 seconds.
"Check engine" light goes out and illuminates again. Release the gas pedal (close idle contact at throttle position sensor).
3. The following flash sequence (fault code) indicates a fault path.

Fig. 47 Self Diagnostic Fault Code Reading:

4. Note the fault code and again press the gas pedal to the full acceleration position for 3-4 seconds. For fault code example see Fig. 47.
5. Repeat step #4 until fault code 1000 (output end) appears.
6. Identify the defective component by using the following decoding chart:


1500 = No fault
1x12 = Idle contact - short circuit to ground
1x14 = Temperature sensor NTC II
1x15 = Idle contact interrupted
1x21 = Air flow sensor
1x23 = Lambda control rich or lean
1x24 = Oxygen sensor
1x25 = Oxygen sensor interrupted
1x41 = Control unit
1000 = Output end


x : If x is a number 1 = Fault present
If x is a number 2 = Fault recorded but not present at this time

Other flashing codes are possible but do not represent a warning.
The fault codes can also be read and erased by using flashing code tester #9268, system tester #9288 or equivalent.

7. Repair or replace the defective component or wiring harness. Also check the wiring harness for good condition and connections. A bad harness can cause fault codes.
8. Erase fault memory by pressing the gas pedal to the full acceleration position for more than 11 seconds ("check engine" light goes out briefly after 3, 7 and 10 seconds).

IMPORTANT
If the gas pedal was depressed during starting, the "check engine" light comes on. As soon as the gas pedal is released during driving, the "check engine" light will go out after 4 seconds.
If the full load switch (in throttle position sensor) is defective, it will cause the "check engine" light to come on constantly. There is no fault code for this defect. In this case the fault must simply be corrected or located by using flashing code tester #9268, system tester #9288 or equivalent.