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ABS Light on 95 K1500

Big T said:
I've installed new oversized rear brake cylinders from the 1 ton dually. That was a good and very cheap mod.

I need to buy a coder reader that pulls ABS codes. Last time I took it to the Stealership, it was $100 to pull the code which indicated the RF sensor circuit was interrupted or faulty. Put in new sensor, nothing. Have since changed bearing and sensor, nothing. Have used a new harness to test it, nothing.

Without a code reader or the DVOM thing they refer to, I'm kidding myself on this.
Click to expand...


DVOM is a digital volt meter an analogue one should work as well I have a couple of different meters in the garage. It is amazing what you can buy from used sites nowadays. BPMV is behind your master cylinder it requires a special tool to engage it when bleeding the brake system.

Here is the code reader I use.

http://www.equus.com/Content/Support/Manual/gmcre.pdf

I also have gmtdscan paid version

Spongy pedal could just be the master cylinder leaking they will leak internally. My brake is not as solid as some other vehicles ie my ford escape or my BMW I really have nothing to compare it to since this is the only truck of this type I have ever driven, but I have no problems stopping with 7k trailer on the back.
 
@tanman_2006 hope you dont mind me adding on to the thread, I figured another K series 1995 6.5L with ABS problems might make for a thread with many possible scenarios, plus all the good tech info from others.

Hey guys,
maiden run out with the 95 K2500HD netted some ABS codes. Brakes felt a tad spongy, and the ABS did not seem to want to work.

I am getting
21 (RF WSS Static)
25 (LF WSS Static)
27 (LF WSS erratic Dynamic)
35 (Open or grounded rear speed signal circuit
12(self check code)

I did notice the lower radiator hose is sitting on the abs harness, that might be an issue.
I had been underneath washing the underbelly, might have gotten some water in the connector on the back of the trans.

Also, I did do the frame and rear intake grounds, but got lazy and did not do the cab ground under the heater hoses. Still need to do the battery terminals and the bolt mod, but when i put the new batteries in (was in a hurry) they looked clean.

I did have the RF wheel in the air, and could not detect any slack in the unit bearing. bearing might be original, I know the CVs are (the joys of stock ride height. :) )

So right now i am pointing towards front abs harness grounding out somewhere, and maybe water in the rear sensor.

Any other places to check?

Also, on a 5 speed 4wd, how many sensors are there on the trans and t-case, and how many are ABS related?

Would it be wise to hire the dealer to flush the system so they can activate the ABS? Fluid looks pretty dark.
 
My 95 k1500 went quite awhile with just cleaning the sensor. Actually pretty sure I never changed it and sold it as is, I know the abs light is back on now. Still no slack in the bearing.
 
in case others come here for info related to abs sensors,, here's more of what I've found, for 95 OBD1
I pulled codes on mine,, I got 21 22 23 25. The light has been on for almost the whole time I've had the truck. the Zone has new ones for 35 ea,,, and I'm doing rotors, new loaded Napa calipers so I thought I'd just throw the sensors in. I seem to remember it working one time, and it took me by surprise. If I dont' like it,, I'll just pull the ABS fuse,,, no light no worries.

what I was wondering,,, is are these soft codes,, that will go away when fixed,,, or how would you clear the abs codes?


Pulling Chevy Truck OBDI Brake Codes Information
Here's information on pulling Chevy Truck OBDI Brakes codes for the RWAL and AWAL brake systems and codes.


PROCEDURE:
Diagnostic Trouble Codes (DTC) 's can be displayed by jumping terminals "A" and "H" of the Data Link Connector and observing the flashing of the "BRAKE" warning light. This should only be done when the brake lamp is "ON".
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 longflash. Include the long flash as a count. Sometimes the first count sequence will be short. However, subsequent flashes will be accurate. If there is more than one failure, only the first recognized code will be retained and flashed.
NOTES:
DTC's 6, 9 and 10 will only turn the "BRAKE" lamp on while the fault exists. These are soft codes faults and can only be read with the Tech 1 scan tool.
Do not jump terminals "A" to "H" if the "BRAKE" lamp is not on. Jumping the terminals with the "BRAKE" lamp off will set a false DTC 9. This will turn the "BRAKE" lamp on and disable the antilock system.

    • 1, 11, & 12 ECU Malfunction
    • 2 Open Isolation Valve or Malfunctioning ECU
    • 3 Open Dump Valve or ECU Malfunction
    • 4 Grounded Antilock Valve Reset Switch
    • 5 Eccessive Actuations of the Dump Valve
    • 6 Erratic Speed Signal
    • 7 Shorted Isolation Valve or Faulty ECU
    • 8 Shorted Dump Valve or Faulty ECU
    • 9 Open Circuit to Speed Signal
  • 13, 14 and 15 ECU Malfunction


The following is a list of the OBD-I trouble codes for the four wheel anti-lock brake system.

*Code 21: right front speed sensor or circuit open
*Code 22: missing right front speed signal
*Code 23: erratic right front speed signal
*Code 25: left front speed sensor or circuit open
*Code 26: missing left front speed signal
*Code 27: erratic left front speed signal
*Code 29: simultaneous drop-out of front speed sensors
*Code 35: vehicle speed sensor or open circuit
*Code 36: missing vehicle speed sensor signal
*Code 37: erratic vehicle speed sensor signal
*Code 38: wheel speed error
*Codes 41 through 54: control valves
*Codes 61 through 63: reset switches
*Code 65 and 66: open or shorted pump motor relay
*Code 67: open motor circuit or shorted BPMV output
*Code 68: locked motor or shorted motor circuit
*Codes 71 through 74: memory errors
*Code 81: brake switch circuit shorted or open
*Code 86: shorted anti-lock indicator lamp
*Code 87: shorted brake warning lamp
 
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Disconnect the batteries, or IIRC, with engine off, trans in drive with a foot on the brake and accelerator with the key in start will clear the codes. It takes 30 seconds?
 
Well I did the repairs,,,,, ABS light went off and stayed off. then the test drive,,, and about every other time I stop, the last 5mph,, the abs act's all goofy, pulsing and vibrating. Not really liking that much. So I pulled te 60amp abs fuse. The new ceramic brake pads, seem to be doing the trick thou!
 
Every gm truck, suburban, etc has horrible track record with abs. Idk why GM cant get it right. Kinda aggravating.
 
NVW said:
Disconnect the batteries, or IIRC, with engine off, trans in drive with a foot on the brake and accelerator with the key in start will clear the codes. It takes 30 seconds?
Click to expand...
NVW said:
Disconnect the batteries, or IIRC, with engine off, trans in drive with a foot on the brake and accelerator with the key in start will clear the codes. It takes 30 seconds?
Click to expand...

I can't tell/nor do I have enough experience to tell whether or not that's a serious response. But I don't care enough to not try it!
 
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