Chevy & GMC Vans

well i finally insured the van this year...fired her up and as soon as i stepped on the brake peddle the ABS light on the dash came on.....today i changed out the front brakes figured it came on due to the brake pads being low.....no go, still on....even tried disconnecting battery to reset the computer but still on......i looked at the sensor itself and it was perfect shape and clean....i did wipe it down, put on dielectric grease and plugged 'em back in. wires were also in good shape........i guess the only good thing that's come of this so far is i got my slotted black rotors on......any thoughts as to what it could be..........

if one of the sensor's has had it......how much do they cost to replace?

has anyone ever tried this? does it work?

READING TROUBLE CODES

See Figure 1
Click image to see an enlarged viewFig. 1: Pinout of the ALDL connector
Rear Wheel Anti-lock Brakes

The trouble codes are read by jumping terminal A and terminal H of the ALDL (assembly line diagnostic link) with a jumper wire. Observe the flashing of the brake warning light. The terminals must be jumped for about 20 seconds before the code will begin to flash.

Count the number of short flashes starting from the long flash. Include the long flash as a count. Sometimes the first count sequence will be short, however, following counts will be accurate.

If there is more than one failure, only the first recognized code will be retained and flashed.

* Code 1-ECU malfunction
* Code 2-Open isolation valve or faulty ECU
* Code 3-Open dump valve or faulty ECU
* Code 4-Grounded anti-lock valve switch
* Code 5-Excessive dump valve activity during stop
* Code 6-Erratic speed system
* Code 7-Shorted isolation valve or faulty ECU
* Code 8-Shorted dump valve or faulty ECU
* Code 9-Open speed signal circuit
* Code 10-Brake lamp switch circuit
* Code 11-Faulty ECU
* Code 12-Faulty ECU
* Code 13-Faulty ECU
* Code 14-Faulty ECU
* Code 15-Faulty ECU

4-Wheel Anti-lock Brakes
EXCEPT 1996 MODELS

The trouble codes are read by jumping terminal A and terminal H of the ALDL (assembly line diagnostic link) with a jumper wire. Observe the flashing of the ANTI-LOCK warning light. The terminals must be jumped for about 20 seconds before the code will begin to flash.

Count the number of short flashes starting from the long flash. Include the long flash as a count. Sometimes the first count sequence will be short, however, following counts will be accurate.

If there is more than one failure, only the first recognized code will be retained and flashed.

* Code 21-RF speed sensor or circuit open
* Code 22-Missing RF speed signal
* Code 23-Erratic RF speed sensor
* Code 25-LF speed sensor or circuit open
* Code 26-Missing LF speed signal
* Code 27-Erratic LF speed sensor
* Code 29-Simultaneous drop out of front speed sensors
* Code 31-RR speed sensor or circuit open
* Code 32-Missing RR speed signal
* Code 33-Erratic RR speed signal
* Code 35-VSS or LR speed sensor or circuit open
* Code 36-Missing VSS or LR speed sensor or circuit open
* Code 37-Erratic VSS or LR speed sensor signal
* Code 38-Wheel speed error
* Code 41-54-Control valves
* Code 61-63-Reset switches
* Code 65-66-Open or shorted pump motor relay
* Code 67-Open motor circuit or shorted BPMV output
* Code 68-Locked motor or shorted motor circuit
* Code 71-74-Memory errors
* Code 81-Brake switch circuit shorted or open
* Code 86-Shorted anti-lock indicator lamp
* Code 88-Shorted brake warning lamp

1996 MODELS

Trouble codes on the 1996 vehicles can only be read using a scan tool. It is not possible to read the trouble codes by the flashing light method. The trouble codes are the same as the earlier year vehicles.
CLEARING TROUBLE CODES

On 1985-95 vehicles the trouble codes may be cleared using a Tech I scan tool or by performing the following procedures. On 1996 vehicles, the trouble codes can only be cleared by the Tech 1 scan tool.

1. Turn the ignition switch to the RUN position.
2. Use a jumper wire to ground the ALDL terminal A to H for 2 seconds.
3. Remove the jumper wire for 2 seconds.
4. Repeat the grounding and ungrounding 2 more times.
5. Check that the memory is cleared by making a diagnostic request.
6. Turn the ignition switch OFF.

here is the aldl connector which needs to be jumped......

I've never done this for ABS brake issues but you do the paper clip thing for the SES light (different pins). Sounds like it should work.

The above system will work and point you in the direction of the problem, my guess will be one of the wheel sensors, try the test and let us know what you find...Johnny

hey guys, well i finally got around to trying this and it does work. when i jumped the terminals the ABS light began to flash......it actually started to flash right away and not 20 seconds later as suggested......it appears it gave me three different codes......codes i got were "5,3,2" in this order......there would be a long pause between codes

looks like it's my dump valve? wtf is that and where is it located? some more research req'd now......

REQUEST TO GET THIS STICKIED SINCE IT DOES WORK AND HOPING SOMEONE ELSE CAN GET SOME USE OUT OF IT VS. PAYING A SHOP TO DO THE SAME THING

LiftedAWDAstro wrote:I've never done this for ABS brake issues but you do the paper clip thing for the SES light (different pins). Sounds like it should work.

so wait, did i do this right......i counted using the long flash as a first count then seperated them with the pauses in between....so is it actuallly giving me three different codes or was i supposed to count them all together until the very long pause which i'm assuming starts the sequence all over again...........

ok, i went and tried again....looks like i'm just trying too hard with this thing.....appears i got 5 and 3.....had long pauses between the two.....i tried clearing it but it didn't take......i guess i have to resolve the issue first then clear it.....

so what is the dump valve and where is it located?

The dump valve is in the ABS unit. I'm pretty sure it is not servicable as a separate piece.

Smiliesafari wrote:The dump valve is in the ABS unit. I'm pretty sure it is not servicable as a separate piece.

ah crap.....wonder what a new one is gonna run?

I bought a complete ABS unit at my local salvage yard for $75.00.

so i just called a gm dealer.....the "dump valve" is a seperate piece located under the ABS unit...no longer available in canada....however can get a remanufactured unit out of the states for................wait for it.................$1600!!!!! ouch.........

I like this post! Maybe it can help what I'm going through. My van is a 2003 Astro, and the ALDL connector is different.

The one shown above is a 12 pin connector (6 top and 6 bottom). Mine is a 16 pin connector--has 8 top and 8 bottom slots for pins. Will the paperclip method work, and which ones do I use?

Paper clip will not work on the OBD-2 vehicles.

theres guys that can fix this for around $60. its just a matter of soldering a few contacts in the unit itself. the hardest part is getting it off of the van, its held in place by 4 #20 torx screws. you can find youtube how to videos on the soldering points if you want to try and do it yourself.