ABS Light on 95 K1500

[tanman_2006]

My abs light came on and I would assume my wheel bearings are suspect to the inner bearing being out. I just did tierods, upper balljoints, and pitman arm and didnt feel any bearing slop in the front end.

Where do I start looking and how do I narrow down which side is at fault?

 

[Big T]

The ABS light on my truck goes on, most of the time. I did recently have a several month stretch where it stayed off, but then a good offroading trip put it back on for good. It will go off on start up, but shortly after I start rolling forward it comes back on. I had the code pulled and it indicated a short in the RF bearing ABS sensor. That sensor has been replaced several times. Last fall that bearing went out and a new one installed. This did not fix it. The other day I tested a new (old) wire harness from our '95 wreck to see if that was the problem and it did nothing.

I don't have a code reader for the ABS, so that leaves me with the choice of going to the dealer and paying $100, or just swapping in parts and testing. 've basically have given up on mine as I'm not going to go back and paying the dealer $100 to pull the code again. Short of the ABS unit itself, I've covered everything on it and still can't figure it out.

 

[tanman_2006]

Mine is fixing to roll over 290K and in the 120K I have owned it the ABS has never came on. I am figuring there has to be a fix since it hasnt been a problem before.

 

[ak diesel driver]

as said a scanner will tell you where to look, doesn't necessarily need to be a dealer.

 

[tanman_2006]

I can't use the paper clip? I'll have to find an obd1 scanner.

Sent from: Source Unknown

 

[Big T]

as said a scanner will tell you where to look, doesn't necessarily need to be a dealer.

Are there any cheap scanners out there for this? Last guy who hooked up a scanner (replaced RF bearing last fall on road trip) said his hand held scanner was $6,000.

 

[Big T]

Mine is fixing to roll over 290K and in the 120K I have owned it the ABS has never came on. I am figuring there has to be a fix since it hasnt been a problem before.

Well, usually it is a simple fix such as a bearing replacement. Mine has defied all of the that and further pissed me off by working intermittently. Scanned it and the code said connectivity or grounding fault in RF wheel and it was a brand new bearing and sensor.

http://www.thetruckstop.us/forum/showthread.php?32497-Tech-2-ABS-Code

 

[THEFERMANATOR]

I can't use the paper clip? I'll have to find an obd1 scanner.

Sent from: Source Unknown

OBD1 ABS can be code read with the paper clip trick, but it isn't very accurate. And a word of warning, many scanners will not read the 95. I learned this the hard way when I borrowed a TECH 1 from the local dealer and discovered that it wouldn't read mine(there tech 1 did up to 94, and there tech 2 did from 96+). To enter the self test you ground the A and H pins to each other. and here is a code chart

 

[Big T]

OBD1 ABS can be code read with the paper clip trick, but it isn't very accurate. And a word of warning, many scanners will not read the 95. I learned this the hard way when I borrowed a TECH 1 from the local dealer and discovered that it wouldn't read mine(there tech 1 did up to 94, and there tech 2 did from 96+). To enter the self test you ground the A and H pins to each other.View attachment 38025 and here is a code chart View attachment 38026

Ferm, do you have that same code chart for OBD II?

 

[GM Guy]

i got some little actron scanner from Jegs I got in roughly 2006 when i got my 91 C1500. supposed to work on ABS codes, has a switch in the end to go from engine code reading to abs system reading.

I have not used this on any 6.5L truck, nor any 1995 truck. I need to try it out and see if it works, as I have an ABS light, and a SES light on after the 3,300 mile round trip.

 

[THEFERMANATOR]

Ferm, do you have that same code chart for OBD II?

No, but I can probably pull up my 01 ABS codes from my donor truck manual(not sure if they're the same or not).

 

[tanman_2006]

Thanks for the codes ferm. Good starting point.

Can't I check if a sensor tests open or something with a multimeter?

Sent from: Source Unknown

 

[NVW]

Yes, I can't remember what the ohm value is supposed to be, but you will find out if it is open.

Thanks for the codes ferm. Good starting point.

Can't I check if a sensor tests open or something with a multimeter?

Sent from: Source Unknown

 

[ak diesel driver]

Are there any cheap scanners out there for this? Last guy who hooked up a scanner (replaced RF bearing last fall on road trip) said his hand held scanner was $6,000.

don't know about price but a buddy of mine owns who his own shop read mine. I know it wasn't a tech 2

 

[GM Guy]

checked the codes on the 95 GMC, and the little actron scanner reads 95. tells me code 37, and code 12.

 

[SnowDrift]

I'll need to be looking at this, too. Mine came on last weekend. First time I've seen it in the 10 years I've owned it - forgot it even had ABS. Thanks for the chart, Fermanator.

 

[haggus]

I had an ABS fault last Dec threw a bunch of codes I ended pretty much changing everything. Once I started getting into it that far it just made sense. Rock Auto sells the sensors they aren't exactly easy to change depending on the amount of corrosion on your front end.

I used a cheap OBD 1 reader it was 30 bucks at Canadian Tire but it works.

Here is some info I found when looking around

http://www.motor.com/article.asp?article_ID=45

As for testing the WSS you need to have access to a DVOM Here is the procedure

Trying to repair the sensor harness will most likely result in faulty signals. The resistance specification for each WSS is 1000 to 3000 ohms, which can be measured at the ECU connector.

For a more dynamic test, you can use a DVOM set to the AC scale. Just connect the meter at the sensor connector and rotate the wheel by hand. The output should exceed 400mV AC.

 

[Big T]

I had an ABS fault last Dec threw a bunch of codes I ended pretty much changing everything. Once I started getting into it that far it just made sense. Rock Auto sells the sensors they aren't exactly easy to change depending on the amount of corrosion on your front end.

I used a cheap OBD 1 reader it was 30 bucks at Canadian Tire but it works.

Here is some info I found when looking around

http://www.motor.com/article.asp?article_ID=45

As for testing the WSS you need to have access to a DVOM Here is the procedure

Trying to repair the sensor harness will most likely result in faulty signals. The resistance specification for each WSS is 1000 to 3000 ohms, which can be measured at the ECU connector.

For a more dynamic test, you can use a DVOM set to the AC scale. Just connect the meter at the sensor connector and rotate the wheel by hand. The output should exceed 400mV AC.

Read the article and have some questions.

I have never been able to solve my intermittent ABS Light, which is nearly always on. After the initial test cycle when I fire up the engine, the ABS light is always off. It usually comes on after rolling a short distance. Sometimes, it doesn't come on and the whole system works.

My brake pedal is spongy. I've always assumed that's just the way these trucks are. However, my son's '94 has a relatively hard brake pedal. So I read this article with great interest.

What's a DVOM?

What's the Brake Pressure Modulator?

>>> The Electronic Control Unit (ECU) of the 4WAL system is attached directly to the business part of the system-the Brake Pressure Modulator Valve (BPMV).

Service

Bleeding the BPMV is rather complex on the Kelsey-Hayes 4WAL system. A pressure or vacuum bleeder is preferred over using the brake pedal for this procedure. If the pedal must be used, consider removing the master cylinder to clean the reservoir, then bench bleed it to flush out any debris. If a new master cylinder is being installed, be sure to bleed it before installation. When vacuum or pedal bleeding, don't let the master cylinder reservoir run dry! Once air is bled from the master cylinder, the BPMV can be bled as follows:

1. Open the internal bleed screws a quarter- to a half-turn. These are the cap screws on either side of the BPMV.

2. Attach special tools (Kent-Moore No. J39177) to hold open the high-pressure accumulator bleed valves.

3. Open the two bleeder screws at the BPMV and bleed the unit.

4. Bleed the wheels in the following order: right rear, left rear, right front, left front.

5. Retighten the internal bleed screws and remove the tools from the high-pressure accumulators.

6. Firmly depress the brake pedal and perform three to six functional tests using either a scan tool or the jumper method described earlier. This forces remaining air from the BPMV into the lines running to the wheels.

7. Finally, bleed all four wheels again in the following order: right rear, left rear, right front, left front, to remove any air that was expelled from the BPMV. Note: This procedure should be necessary only if the BPMV is being replaced. During routine service, the system can be bled normally at the wheels.

If the BPMV is replaced and the procedure just described is not followed, air may be trapped in the hydraulic circuits that are normally not exposed to the regular braking system. Only after an ABS stop will this air be introduced. That means it may be days or even weeks after the fix that the customer returns with a spongy brake pedal complaint, not to mention one unhappy disposition. Now that's a sobering thought, isn't it?

Could the BPMV be the reason for my spongy brake pedal and ABS light coming on?

 

[tanman_2006]

This describes mine too. I blame mine on leaky brake cylinders on the rear end. They need changed but I have a 14 bolt FF w/ 3.42 rears and 3.5" brakes that will get transplanted along with the whole A Arm assembly, axle, and 8 lug hubs from Ol' Blue. (the 8 lug conversion will help motivate me on the D60 for Ol' Blue.

 

[Big T]

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.