A request for a specific fault related to the operation of the oxygen sensor in the exhaust gases can only be made after a test drive lasting at least 10 minutes, if no other fault occurs.
The ROM also remembers faults caused by temporary damage to the wiring or contacts. If such faults do not recur within approximately eight engine starts, their codes are automatically erased from the memory.
Request for fault codes entered in the ROM. The fault codes entered in the ROM of the electronic control unit are displayed using a control lamp located in the instrument cluster (Fig. 2-68). When the ignition is turned on, the lamp lights up. After the engine is started, if no serious faults in the engine operation are detected, the lamp goes out.
When polling the contents of the self-diagnostic system ROM, the malfunction indicator lamp should flash.
Display of fault codes. When interrogating the self-diagnostic ROM, four-digit fault codes are displayed as a sequence of groups of flashes of the fault indicator lamp with intervals between the groups of flashes lasting 2.5 seconds, during which the indicator lamp does not light. Each character of the four-digit code corresponds to a number or group of flashes from 1 to 4. If no faults are detected in the system, the code 4-4-4-4 is displayed. At the end of the display of the code sequence, the code 0-0-0-0 is displayed. In this case, the indicator lamp flashes at constant intervals of 2.5 seconds.
Entering fault codes into the control unit ROM occurs only when the ignition is on.
The four groups of flashes of the requested fault code appear after the output of a start signal, during which the indicator lamp lights up, and a pause of 2.5 seconds, during which the indicator lamp does not light up. After the output of the fourth group of flashes, another pause of 2.5 seconds follows. The corresponding flash code is then marked by means of a start signal until the ignition is switched off or the engine speed exceeds 2500 rpm.
Example:
- the control lamp lights for 2.5 sec;
- the control lamp goes out for 2.5 s.
The starting signal is given:
- the lamp flashes twice;
- the lamp goes out for 2.5 sec;
- the lamp flashes three times;
- the lamp goes out for 2.5 sec;
- the lamp flashes four times;
- the lamp goes out for 2.5 sec;
- the lamp flashes twice;
- the lamp goes out for 2.5 sec.
Thus, the code 2-3-4-2 is issued. After this, the cause of the malfunction is determined according to the table of malfunction codes. After eliminating the malfunction, the code of which was entered into the ROM, its code should be erased from the contents of the ROM.
After this, the ROM is again polled for the presence of the next fault.
Interrogation of the fault ROM. When interrogating the fault ROM, the following sequence of operations must be strictly observed:
- demand ROM faults:
- troubleshooting the detected fault;
- erasing the code of the corrected error from the contents of the ROM;
- new poll of the fault ROM.
Thus, a request to detect the next malfunction is possible only after the previous one has been eliminated and its code has been erased.
If no other fault is detected, perform a new interrogation of the fault memory after a test drive of at least 10 minutes.
In this case, the fault ROM interrogation is performed as follows: Check the reliability of all wiring connections, the serviceability of the fault indicator lamp and fuse N918. Start and warm up the engine to normal operating temperature and leave it to idle. Do not increase the crankshaft speed during the checks.
The original information is posted on the website (vwmanual.ru)
Note: If the engine does not start, before starting the test, turn on the starter for 6 seconds and leave the ignition on.
Move the gearshift lever protective cover up and connect the red terminal "1" of the connector located next to the gearshift lever with a 5-wire ground connection (Fig. 2-69). On vehicles that do not have such a connector, connect the yellow-black wire of the ignition coil connector with a wire to the ground for at least 5 s (Fig. 2-70). The system malfunction indicator lamp in the instrument cluster should start flashing.
Count and record the number of blinks in each group. Eliminate the detected malfunction.
Erase the code of the eliminated fault. Continue checking until the code 0-0-0-0 appears, indicating the end of the fault code display. The output of the code 4-4-4-4 means there are no faults in the injection system.
Erase contents of fault memory. Switch off ignition. Connect red terminal of connector or yellow-black wire of ignition coil connector to ground with wire. Switch on ignition. After 5 s disconnect ground wire. Code of previous fault is deleted from fault memory.
Note. The table of fault codes also contains instructions on how to eliminate them. The last column of the table indicates the stages of checking the electrical circuits of the system through the terminals of the ECU connector according to the table below "Checking the electrical parameters of the SCV "Mono-Jetronic" through the ECU connector terminals".
Codes 2-3-4-1 and 2-3-4-3 can only be erased by disconnecting the electronic control unit connector for at least 30 s.
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