Why do people buy Saabs? Over the years Saab has enjoyed a loyal cult following. That fact, along with being bought out by General Motors, has helped secure a modest share of today’s automotive marketplace for the manufacturer. Realistically though, you are not going to see the Saab 900 unanimously voted in as one of the top 100 most stylish cars built in the 20th century. So, what is the attraction?
What they have going for them is anvil-like dependability and longevity. These trendy vehicles with quirky “ignition key in the center console” type idiosyncrasies just don’t break down very often. But when they do, working on them will teach technicians an unforgettable lesson in patience and perseverance. In fact, there is a saying among a lot of technicians about working on a Saab, “When a Saab comes into the shop for repairs, that is what you do — sob, then try to hide.” With that in mind, I’m offering you, the last to cry and flee, a very useful electrical tech tip concerning the enigmatic 1989 to 1993 Saab 900.
In 1989, Saab 900 models received a new gear selector switch featuring a diode that allowed an idle increase signal to the engine control module when the automatic transmission was put into reverse. Upon replacement or removal of the gear selector switch or any of its connections, there is a danger of mistaking the electrical leads and transposing them.
When this happens, the fuel injection system will receive a continuous idling increase signal of +12 volts across the diode. This causes the idle to run several hundred RPM higher than normal and the backup lights will be switched on even when the gear selector is in position (D) or (2). Sometimes the increased current through the diode will be too high for it, and it will become unserviceable.
The vehicles affected by this problem are the 1989-1993 Saab 900 models with an automatic transmission and cruise control. Listed below are the symptoms you may experience and their possible causes or diagnostic checkout procedures.
Symptom 1: The backup lights come on when the gear selector is in position (D) or (2) and the idling increase function is continuously engaged.
Possible Cause: The diode is OK but the leads to the backup lights are not connected correctly.
Symptom 2: An inoperative idling increase function and cruise control system.
Possible Cause: The diode is not OK and the leads to the backup lights are not connected correctly.
Symptom 3: No Idling increase with the gear selector in the (R) position, the diode is good and the leads are connected correctly.
1. Inspect fuse 8 for the cruise control and fuse 13 for the backup lights to make sure they are both good. They are located in the main fuse box in the engine bay.
2. If they are good, then carefully remove the gear selector indicator cover and undo the selector lever center console at front and rear.
3. Check the electrical connections on the gear selector switch as illustrated in Figure 1.
The White cable should be connected to pin 2.
The Blue/White and White lead should be connected to pin 1.
If the leads are not connected correctly, change them as stated.
4. Connect a voltmeter to the Orange lead connected to pin 3 and a good grounding point, such as the gear selector lever housing. Turn the ignition switch to the “On” position. The meter should now show battery voltage in the (R), (D) and (2) positions and 0-5 volts in the other positions.
If the meter shows 0-5 volts in position (R) and battery voltage in positions (D) and (2), the diode is bad and a new gear selector switch, P/N A 95 64 733 should be fitted.
If the meter shows battery voltage in all positions, the leads to the backup lights are not connected correctly. Switch the leads and take a new reading.
If the meter shows 0-5 volts in all positions, the diode is not OK and the leads to the backup lights are not connected correctly. Fit a new gear selector switch and make sure the leads are connected correctly.
NOTE: When fitting a new gear selector switch, move the selector lever to the (N) position. Turn the switch housing so that the switch lever is opposite the mark on the housing. Tighten the contact housing’s two retaining screws.
5. Check the operation of the switch as in steps 3 and 4 above.
6. Refit the selector lever center console and selector lever indicator cover.
There, that wasn’t so bad. Remember to drive the car and check the operation of the backup lights, neutral safety function, idling increase function and the Cruise Control. After tackling and repairing an electrical problem like this on the quirky Saab 900, everyone in the shop will come out of hiding and of course, be in awe of your genius.
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Written by ALLDATA Technical Editor, Rich Diegle. Rich is an Advanced Engine Performance Certified, ASE Master Technician with an AA Degree in automotive technology and 22 years of dealership and independent shop experience.