I have 98 cummins 24 valve and the abs and brake light illuminate about 2 minutes after start up. This problem started immediately after I replaced my defective ECM with a used one. Two dealers said this problem occurs because the replacement ECM does not match the VIN of my truck. Otherwise truck runs and STOPS OK. Are the dealers trying to sell me a new ECM or is there a way to program the used ECM to turn the lights off. Both dealers tried flashing, but to no avail. ???

 

mine always does it when I'm sitting @ a stop light. The abs switch is linked up to the vacuum pump (at least on my 95) right on top of the left fender. Its a little silver rectangular box with a small 1/8&quot; hose on one side and some electrical connector on the other right near the master cylinder. if you disconnect the electrical connector the abs lamp goes out.<br>I think it has to do with low vacuum but I may be wrong. but it seems to me that mine is good for a couple of brake applications B4 I lose vacuum and go straight to armstrong breaking or footstrong breaking.<br><br>Please correct me if I'm wrong<br><br>Mitch

 

correct me if I am wrong but I think that the abs is it's own computer pretty much seperate from the other computer at least that is the way my 95 is. I had a pretty much the same problem but my abs light would not go out and the brake light would come on as soon as I hit 30 mph. Mine was a faulty speed sensor on the rear end you can check these with a ohm meter and rotateing the tires. Also the vacuum have a problem with rubbing a hole in them I pulled the one off of the low vacuum switch with the truck not running and blew on it and could hear the leak in mine. when you do this move the lines around cause they might only leak in a certain position. Matt

 

Check for a vacumm leak. The plastic vac lines lines have a bad habit of chaffing through. If you get a large enough hole, you will get those lights at start up and sometimes at idle.<br>There are only a couple of vac lines under the hood, so not real hard to trace.

 

Thanks for the info

 

Those two dealers are correct. A Vin mismatch will throw a ABS code for exactly that reason. Although I,m not sure if you have to replace the PCM for this,(you may). You can first have them go back into the PCM with a DRB(Diagnostic readout Box) and see if you can put the correct VIN back into the used PCM,but i have only seen this replacing a new PCM,one that contains no VIN yet,and i'm not sure if one is already there,that you can reinput a new VIN. TGCTD