My 1999 Montanna extended length just threw the ABS, TCS and BRAKE warning lights. TCS will not engage. All fuses are good. Looking at the Service Manual see there is a EBCM relay in the power feed to the ECBM. Know that the ECBM in many GM cars fails and causes this symptom. Haven't read codes yet but suspect the ECBM as the culprit. My 1998 Corvette has a similar ECBM and TCS minus the ECBM relay. The Vettes have been known to have the ECBM fail losing all ABS and TCS until the module is fixed or replaced. Did see a post on a forum that said the owner had problems with the connectors on the wheel sensors. Haven't pulled anything yet but what you suggest?

 

Being a pontiac i would start with the wheel bearings on the front common in these vans

 

Update:
Pulled front wheels and using a DVM checked resistance of sensors and wiring harnesses. Both sensors read about 1080 ohms which is in the middle if the specs in the GM Helm Service Manual. No shorts to ground. On harness end both harnesses read about 40K from pin to pin and no shorts to ground. Schematics show harness going back to first connector on ECBM. With ignition ON and sensors connected get no dash lights until starting the car. Then ABS, TCS and BRAKE lighs all come on steady.
When I had both sensors disconnected to make resistance checks I turned ON the ignition. All 3 lights came on as soon as ignition was turned on and remained on when starting the car. After replugging the sensors the conditions were the same as I first listed above. Used a Taptok TP-300 scanner. Could not SEE any codes. Went to Advance Auto and tried their new Actron scanner and once again NO CODES.
Saw specs on a Geniscan MaxScan VAG405 scanner on www.alpha-bid.com which is geared toward VWs and Audis. the Comparision guide says that this scanner with advance features also reads ABS, airbags, auto trans, and service reset functions but upon further reading I'm lead to believe that these functions are only for the specific VW protocol not for all OBD buses.

What do I do NEXT? BIGHANK

 

Update 2
Pulled ECBM and checked resistances to wheel sensors and fuses. Checked Brake Module Relay and verified 12 v coming from it to the EBCM and the soleniod relay. Reassembled and turned on ignition. After bulb check ABS, TCS, and BRAKE lights all went off. Started car. LIGHTS STILL OFF. Then stepped on the brake. ALL 3 LIGHTS COME ON AND STAY ON. Hear 2 thumps in front left side. Think it might be one or two of the solenoids. Don't want to replace a NON-DEFECTIVE ECBM or solenoid or modulator but can not retrieve the ABS codes. Any ideas what to do NEXT?[]BIGHANK

 

Hi everyone. I had a similar issue with my Saab 93. It was the ABS control module. All of the major electronics for the Saab went through it, and that is why all of the lights come on. I imgine that is also why the air bags and other items you mentioned are coming up as faults.

If that is the same in your case, you can send it down to Auto Truck Electronics in Florida and they will rebuild your module. For me, it wasa savings of about 3,100.00. They rebuild the part for about 250 while Saab sells the part for 2,800.

I am not familiar enough with the Montana to be sure, but it is at least another avenue.

 

I am having a similar problem with mine. Please post up what your results are so I can have somewhere to go. I was going to try a few things as soon as all this rain stops.