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Home >> Saab >> 1994 >> 900 Turbo Convertible L4-1985cc 2.0L DOHC Turbo EFI >> Repair and Diagnosis >> Technical Service Bulletins >> All Technical Service Bulletins >> ABS System - Diagnostic Procedures >> Fault Code Retrieval Procedure

Fault Code Retrieval Procedure




Note

A. Select Valve Test mode to confirm proper/faulty functlon of the inlet valves, outlet valves or main valve.
B. Select Monltor mode and the desired wheel sensor to confirm proper/faulty function of the wheel sensors. Drive the car under varying conditions, such as over railroad tracks, sharp turns, etc. Observe the display and note any irregularities.

1. Park the car, set the handbrake, and turn off the ignition.

2. Connect the jumper lead to the diagnostic plug with the switch set in the "ON" position.

3. Turn the key to the "run" position.

4. Move the jumper switch to the "OFF" position and watch the ANTI-LOCK warning lamp.

The ANTI-LOCK warning lamp will now begin to flash. The flash code sequence will always begin with a long flash of about 2.5 second duration, followed by a 2.5 second long pause. The pause is followed by a series of short flashes (approx. 0.5 seconds) for the first digit of the four-digit code. The number of flashes is equivalent to the digit, i.e. one flash = 1, two flashes = 2, etc. The flash sequence for the first digit is followed by a 2.5 second long pause before the next sequence of flashes begin for the next digit. This pattern is repeated until all four digits are displayed for the first fault code. The fault code should be wriften down on a piece of paper as it is retrieved.

In order to interrupt the retrieval, either move the jumper switch back to the "ON" position or turn the ignition switch off.
5. If there is a fault with any valve, the fault code may be displayed only once, and then the ANTI-LOCK warning lamp may stay lit constantly. In order to display the code again, the read out procedure must be repeated from the beginning (steps 1-4). Corrective action must be taken on the indicated fault and the fault code must be erased (see step 7) before the next fault code can be retrieved. If there is a fault with any wheel sensor, the fault code sequence will repeat itself continuously with a 2.5 second long flash and pause between each series. To retrieve any additional fault codes, move the jumper switch to the "ON" position for at least 2.5 seconds before moving it back to the "OFF" position at which time the next fault code will be displayed.


6. When all stored fault codes have been displayed, the ANTI-LOCK warning lamp will display a continuous series of 2.5 second long flashes and pauses (Code 0000).

If the jumper is switched "ON" and "OFF" again, the warning lamp will display a continuous series of short flashes and pauses which means that the fault must be corrected and the fault code erased.

If no faults have been stored into memory, fault code 4444 will be displayed during retrieval.

7. In order to erase fault codes, the codes must have been retrieved at least once and the read-out procedure brought to the end such that code 0000 has been displayed. After that has been done, the jumper lead should be removed from the plug and the car driven at a speed higher than 20 mph.


If a fault remains in the ABS system, the ANTI-LOCK warning lamp will be illuminated constantly.
Warning Light Illumination Without Fault Code Storage

It is possible the ANTI-LOCK warning lamp will illuminate without a fault code being stored in the ECU. The circumstances under which this can occur are as follows:
Improper Installation of the ECU: If the ECU is not installed in the main 35-pin connector, or If the main connections are loose, and the ignition is switched "ON," the system relay will not be energized. The warning lamp will be illuminated through the resting contacts, pins 1 and 3, within the relay. Also check that the fuses and wiring supplying power to the ECU are ok.

ECU failures: With some ABS hardware faults, the ECU will be switched off internally, cutting off power to pin 8 of the ECU, thereby de-energizing the system relay and illuminating the ANTILOCK warning lamp through the resting contact within the relay. Since the main power to the ECU through pins 3 and 20 is no longer present, the ECU is no longer able to store any fault codes. If there is a fault within the ECU circuit which controls the warning lamp function, the lamp will either be incapable of being switched on or will be switched on constantly, depending on the type of internal failure. It may also flicker randomly
during any given ignition ON/OFF period. If this type of fault is suspected, try a known good ECU.

Short circuit of diagnostic plug: If the circuit for the diagnostic trigger, from pin 26, is shorted to ground, the ECU will enter its diagnostic output mode when the ignition is switched on and if a fault code had been stored into memory. If the car is driven with this type of short, the ECU will be switched off internally as well, and the warning light will be illuminated through the system relay.

Warning lamp faults: If the wiring for the warning lamp is shorted to ground, the lamp will be illuminated even though the ABS is still functional. The ECU is not capable of recognizing this type of short circuit. If the warning lamp has failed, or if there is an open circuit in the wiring for the lamp, the lamp will not be illuminated at all. If the light does not come on during normal starting of the car, this type of fault should be investigated and corrected.



Fault Codes
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