Hi All,
This is my first post so first of all a big thanks for all the great info from very knowledgeable people in the forum. It has been a great help to me as a first time owner of a gmt400. 1991 Work Truck.
After having sorted several TBI issues like ignition control module replacement after reading up here in the forum I was left with an Red brake light in the dash. paper pin showed 3 short an one long wich i understand is a code 4. Grounded reset switch. After hours of googling and reading here all i got was A, RWAL is crap take it away or just unplug it, B, It is not a serviceable item by a new combination valve if you really want it working. But some videos on the net shows that the two round pots can be pried off and the one can remove the electrical part. So I double checked the error code by measuring the resistance between the blue wire on the connector and the valve body and sure enough it was grounded almost no resistance. Got the 2 round caps off removed the white plastic piece with the electromagnetic spools in them and sure enough, in the small middle connector to the reset valve there was some black gunk. cleaned it out, cleaned everything else and put it back together. Now the resistance between the blue line on the connector and valve body was infinite. Removed power to the ABS module to clear the error and it did not come back! $160 saved!
Apologies if this is old news, and hope i don't come across as presumptuous to come with a write up as my introduction post but as i could not find the info i thought someone might benefit from it.
BTW it was all done without removing any pipes and having to bleed the system. The pots are quite tight, some not so gentle prying is required
This is my first post so first of all a big thanks for all the great info from very knowledgeable people in the forum. It has been a great help to me as a first time owner of a gmt400. 1991 Work Truck.
After having sorted several TBI issues like ignition control module replacement after reading up here in the forum I was left with an Red brake light in the dash. paper pin showed 3 short an one long wich i understand is a code 4. Grounded reset switch. After hours of googling and reading here all i got was A, RWAL is crap take it away or just unplug it, B, It is not a serviceable item by a new combination valve if you really want it working. But some videos on the net shows that the two round pots can be pried off and the one can remove the electrical part. So I double checked the error code by measuring the resistance between the blue wire on the connector and the valve body and sure enough it was grounded almost no resistance. Got the 2 round caps off removed the white plastic piece with the electromagnetic spools in them and sure enough, in the small middle connector to the reset valve there was some black gunk. cleaned it out, cleaned everything else and put it back together. Now the resistance between the blue line on the connector and valve body was infinite. Removed power to the ABS module to clear the error and it did not come back! $160 saved!
Apologies if this is old news, and hope i don't come across as presumptuous to come with a write up as my introduction post but as i could not find the info i thought someone might benefit from it.
BTW it was all done without removing any pipes and having to bleed the system. The pots are quite tight, some not so gentle prying is required
