After studying the forum and experiencing for myself I have decided to post the following on the 3 Omigos ( ABS, Traction Control & Down Hill Decent dash warning lights coming and going at will.). It would seem from others who have experienced this problem that there are many fixes. Eg. If the down hill light comes on by itself then the problem can be in the switch/ wiring on the gear lever under the rubber boot. If the ABS light comes on then the ABS unit may be defective. The brake light switch may also cause one of the lights to come on etc, etc.
My Daughters 1998 Turbo diesel 144,000 kms has had the 3 lights coming and going for years with no apparent side effects. When I was preparing the vehicle for resale I had all the wheels off for repainting. This made it easy to remove the wheel sensors located in the axle housings just behind the wheels. The four sensors are identical and have a pig tail about 400mm long and plug into the wiring loom. The left front one plugs in behind the battery and the right one is behind the ABS unit under the bonnet. The rear ones are under the plastic wheel arch covers. I removed then and checked their resistance with a multi meter. I understand that the resistance should be between 1000 ohms and 1500 ohms. These were all 950 ohms. I cleaned them and polished the corrosion off the end of the sensors, and then pushed them back into the housing. I used some grease on the side only to assist with water proofing.
Guess what!! The problem is fixed. The ABS light also goes out after the vehicle reaches 7 Km / hour. This is what is expected according to the owners manual.
Special Guess what!!! It now smiles and waves to me from the front row of a car dealer ship. Thankyou all for your assistance over the past year.
