9000 ABS CODES AND DIAGNOSIS UP TO 93 MY

PRE-90 MY 9000s WITH ABS

The 88 and 89 ECU has no diagnostic capabilities incorporated into it. Disconnect power from it and it loses all memory. This was a problem even at the dealer with the first ABS Tester. You had a car with a light on and to connect the tester to it, you had to disconnect the computer and hook the tester in. Then you had to drive until the problem returned and set the code again. Often, the code would not reappear until a couple of weeks after giving the car back to the customer telling them you couldn't find anything. Then they were mad and a little less confident in our abilities. You can't fix something that isn't showing symptoms. If the light goes out, everything is working and all will check in spec, there's nothing to find.

In 90, Saab added the necessary capabilities to the computer. Codes are retained even if power is lost. The good news for the 88 and 89 is that you can swap the newer computer into it to catch its code with a simple modification that harms neither the 88,89 system or the 90 ECU. You just have to drive it with the added wire at pin 26 with the 90 ECU until the light comes on and then fault trace. If you drive it and the light doesn't come on, reinstall the 88,89 ECU. If the light is right back on, you got a bad ECU.

If you have a 88 or 89 and don't have access to the 90 or up ECU, you can still fault trace your wheel speed sensors as outlined below. If the ABS light comes on and doesn't go off on start up before moving, you have a problem besides the wheel sensors. All you can safely do is check the fluid level and / or inspect the ECU for water ingress by unplugging it and looking for water. Water and ECU's don't get along. There is also a possibility of a diode problem. Read on.

FAULT TRACING

On all cars, wheel sensor codes will reset by cycling the key with the car stationary. They won't reset until the car exceeds 20 Km/hr. If the cars start up and the ABS lights come on and go out before you move the car and then come on after a short time of driving, suspect the sensors. They can also come on on cornering. Again the sensor can be faulty, but wheel bearings and wiring harnesses become suspect as well with this behavior. To check the sensors, get the wheel for that sensor off the ground so that you can spin it. You need to do three tests on each sensor. First check for continuity which should be 800-1400 ohms and within 10% of each sensor. If out of tolerance range, replace the faulty sensor if the harness checks good. Then if resistance is good, do a wiggle test along the length of the sensor to check for a broken wire that is coming and going. Watch the meter for an open or low ohms while tugging on the harness. An open would be a broken wire, low ohms a shorted wire. The last thing to do is an AC voltage test out of each sensor. Since this will change with speed, the best thing to do is spin each wheel at approximately the same speed at each one and look at the ac voltages produced, and compare them to each other. The faulty sensor will be different from the others. Again the range is all sensors within 10% of each other.

Sensor pin numbers at the ECU (ECU located under the left hand false bulkhead cover in the engine compartment) Use a voltmeter/ohm meter for the tests. Take all measurements from the rear of the ECU connector, with the ECU disconnected. Disassembly of the connector is necessary for the pin checks. Use a small flat screwdriver to remove the rubber seal surrounding the harness where it enters the connector(pry rubber off connector only). Clip the tie wrap securing the harness to the connector cover. Remove the Phillips head screw in the connector. Remove the rubber seal inside the connector on the side that plugs into the ECU. Pull the pins out as a whole from the cover, pulling wires through it enough to access rear of pins. Here also you will be able to see numbers on the plastic for the pins

Left Front Pins 5 and 23

Right Front Pins 7 and 25

Right Rear Pins 4 and 22

Left Rear Pins 6 and 24

If a resistance reading is bad, trace to connector for that sensor, fronts are close to the bulkhead near each strut tower, rears are under the rear seat on each side.

They are round black connectors, sort of resembling radio DIN connectors. Unplug and look for corrosion and clean. Reconnect and recheck. If still bad, unplug and jumper the computer side of the connection together and check for continuity which should now be less than 1.0 ohm. If good, remove jumper and check for open circuit(should have open not connected and no jumper). This last thing checks for a short in the harness. If the harness checks good and the circuit bad with the sensor plugged in, replace the sensor.

If you get a sensor code and the sensors all check good, remove the sensor and look through its hole in the spindle and look for damage to the ring teeth that the sensor reads off of. You can find sensor by looking for the wire running down a front strut and tracing it down to the sensor. After you located a front sensor, the rears look similar. The sensors are held in with a 10 mm bolt. Sensors exposed to salt run the risk of corrosion in the space between them and the spindle they mount in. This is a small space and as the corrosion builds, it tends to crush the sensor, often doing so until the sensor no longer works. The corrosion will also make getting the sensor out a chore. WD-40 and turning the sensor is the best approach. Spindle/axle removal and driving the sensor out from the bottom may become necessary. Missing teeth, or stray metal will cause a false sensor code. If teeth are damaged, they must be replaced. Cleaning the hole and the sensor and the teeth with brake clean won't be a bad idea if you get this deep. Neither would a shot of contact cleaner on any connection you come across.

Check the fuses in the engine compartment fuse box for ABS. If there is a problem here, a diode under the box is probably responsible. You can check these and replace as well. If they check good, you should take the car in to be repaired.

There are three diodes of B4 252 GP G1 type. Saab has them under part number 4424172. Radio Shack may have them as well. They are all three the same. Both your cars will check the same way. Unplug ECU. Unplug Pump motor connector, located under the reservoir at the pump. Remove the main relay from the ABS fuse box. Measure voltage drop(diode test mode on good meter will work too) across the diode at pins 20 and 27, negative lead to 20 and positive lead to 27. If you have less than 0.4V, you have a short. If you have about 0.5V, the diode is ok. If you have more than 0.6V, there is no continuity. Reverse the leads. If you have 0.0V there is a short circuit in the diode. If you have OL on meter, the diode is ok. If either no continuity or short, replace diode. Do the same test on pins 1 and 32 with the relay back in, but the other things the same. Use the negative lead on 32 and positive on 1 for the first reading and reverse for the second.

CODE RETRIEVAL

To make the 90 ECU(computer) diagnose the 88/89, remove the 88/89's computer. It is located under the left plastic panel above the firewall behind the false bulkhead. A clip usually holds it in place. With the key off, remove and unplug the ECU and put aside. There was a campaign to install a plastic cover to protect the ECU from water ingress. If yours was not done, turn the ECU upside down and watch for any water running out. Depending on how long the water has been there, it may dry out and be fine, then again it may not. If it doesn't appear to have any water damage, at least wrap it and its connector in Saran Wrap or equivalent to keep it dry when you finish with this repair. Remove the 90's ECU in the same way. Look in the newer ECU where the connector goes. There are 2 pins extending in from the metal to the connector. These are locating pins for the 90's connector. It is made to accommodate them. The 88/89 is not. Push them out from the inside out and put aside for later installation. A flat screwdriver will do the trick. You will need to find a pin connector to fit the connector or a way to secure a wire in position 26. You will have to remove the back of the ECU's connector to install this wire. You will have to secure it so that it will not short other wires or pins or touch ground while you drive the car. Just run this wire out the harness, install the 90 ECU and drive until the ABS light comes on. Then stop the car, turn off the key, ground the wire you installed, turn on the key, and unground the wire. The ABS light will then flash you the code(s). They will be 4 digit codes. It will begin with a 2.5 sec ON and then a 2.5 sec off light. Then the codes will come, one digit at the time, with a 2.5 sec pause in between each digit. Depending on what the fault is, retrieving the next code will take different approaches. I will include the codes for the wheel sensors. If you get another code, I recommend you get a qualified tech to fault trace other codes. WITHOUT A 90 -93 ECU TO SWAP INTO THE 88/89 CARS, YOU CAN'T PULL CODES

Left Front 1233

Right Front 1241

Left Rear 1311

Right Rear 1243

If you get one of these codes, you can reground the wire you added and then unground to go to the next code. Any other code you get will have to remedied before the ECU will give any further codes. This prevents other codes that may be triggered from the first and insures the tech follows the correct sequence in fault tracing.

If no codes have been stored, code 4444 will be displayed. If all codes have been displayed, the light will do the 2.5 sec on, 2.5 sec off over and over (code 0000).

To erase the codes, you must retrieve them once and get to the end of the code procedure( see code 0000). Then remove the wire and drive the car at a speed higher than 20 mph. If a fault remains, the light will illuminate. If they have been repaired it will go out.

You don't have to use the added wire for the 90, it has its own diagnostic plug located near the ABS ECU where the main wiring harness passes through the false bulkhead. It is a small blue plastic connector with nothing plugged into it, just two wires dead ending. To get the codes, you turn the key off, add a jumper wire across the pins in this plug, turn the key on and remove the wire. The ABS light will then flash codes.

A good tool to make to use for this procedure is taking a simple on/off switch and using it to toggle between ground and unground on the 88/89 or jumpered and unjumpered on the 90. Connect one end of its wire to the wire you put in 26 on the 88/89 and the other end to ground. To start the sequence on the 88/89, turn the key off, switch the switch to on, turn the key off and switch the switch off. Codes will come. Do the same thing on the 90 except wire the switch across the diagnostic connector. Since the ECU will react every time it sees ground on pin 26 and restart the code sequence, the switch eliminates the possibility of you inadvertently touching ground with a bare wire.