"Service ASR" & 'Service ABS" lights

[92whiteZ]

My Z has started a strange habit of turning on the "Service ASR" & "Service ABS" lights on every so often. Its only while I am out driving it and it isn't every time. Upon initial start up the lights go through their normal check and then stay off until something goes funky and the come on.

Turn the car off and after restarting the lights are off. They don't always come on and havent been able to reproduce them coming on under controlled circumstances.

Is this an indicator something is about to go out? I have a Genisys scan tool but honestly doesn't read the OBD 1 cars that well. need to save up for a Tech1. Have not pulled any codes as I haven't had the scan tool connected when the lights have come on.

Anyone experience something similar?

thanks

[GOLDCYLON]

My Z has started a strange habit of turning on the "Service ASR" & "Service ABS" lights on every so often. Its only while I am out driving it and it isn't every time. Upon initial start up the lights go through their normal check and then stay off until something goes funky and the come on.

Turn the car off and after restarting the lights are off. They don't always come on and havent been able to reproduce them coming on under controlled circumstances.

Is this an indicator something is about to go out? I have a Genisys scan tool but honestly doesn't read the OBD 1 cars that well. need to save up for a Tech1. Have not pulled any codes as I haven't had the scan tool connected when the lights have come on.

Anyone experience something similar?

thanks


Easy things first... Check your brake master fluid level

[92whiteZ]

yeah I looked at that too. I recently flushed all the lines when I put on the GS calipers, new pads & rotors. So the master cylinder is full.

And this just popped up, I had a few hundred miles on the new brake set up before the lights started coming on. unless I somehow have an air bubble that was hiding in the system that found its way to the abs controller....

that's why i find it slightly odd.

[GOLDCYLON]

yeah I looked at that too. I recently flushed all the lines when I put on the GS calipers, new pads & rotors. So the master cylinder is full.

And this just popped up, I had a few hundred miles on the new brake set up before the lights started coming on. unless I somehow have an air bubble that was hiding in the system that found its way to the abs controller....

that's why i find it slightly odd.


Thats entirely possible (Air in the system) I suggest a good bled of the system again to just rule that out. Ive done your exact brake setup on my car and nary a problem.

[Schrade]

Have you moved the Spark Plug Wires recently?

If they're mis-routed, they can emit EMI - same as a nuke, and solid state sensors and nukes don't get along. (me either - I'm fresh out of SPF nuclear strength) :mrgreen:

[92whiteZ]

these are all good tips. thx

I have not moved the spark plug wires recently. I did change the plugs but didn't put new wires on. and it appears all the OEM wire looms, etc are still in place.

I will tinker with it this weekend and see if I can consistently recreate the problem.

[Jagdpanzer]

Are all your tires the same diameter?
Had the same alarm lights trip on my 94 when taller rear tires are installed.

[92whiteZ]

So I did some experimenting this weekend. Under normal driving conditions the abs/asr lights stay off. Even under moderate braking. But any big braking where the body shifts heavily to the front, the abs/asr lights illuminate and even the brake light in the gauge cluster will illuminate briefly. Like the fluid is sloshing around in the master cylinder, uncovering the sensor. The MC is full with fresh fluid.

Am I correct to presume there is air trapped in the system? I just bought a tech 1a. Is there a means of cycling the abs controller to help move fluid through it?

Once the tech 1a arrives I will pull the codes. What is interesting is the lights dissappear every time the car is turned off. And stay off until I make a hard braking move where the weight shifts forward.

I am running shelby wheels which what I presume are correct
+1 sizing.

Thoughts?

[Schrade]

I am pretty sure that if there's air in the MC, it CANNOT be cycled down the lines, to purge. I THINK the lines have to be dis-connected to properly purge air from the MC, and AFTERward, the air that might be in the lines. Could be wrong tho here'... I think 2 tubes should be connected to the MC OUTputs, back into the MC reservoir.

http://i1.ytimg.com/vi/kEPXgDGU6_0/maxresdefault.jpg

Did you get di-electric grease in the SP wore boots? This high energy ignition system will readily discharge EMI, if ANY resistance is encountered, I do believe here.

[92whiteZ]

When I flushed and bleed the brakes I used a snap-on brake machine that has vacuum lines attached to the bleeders and low pressure at the MC with fluid. I don't think any air got trapped in the MC but who knows.


I did change the plugs recently and have yet to put dielectric grease in the boots. will do that this weekend. that's a good thought, thanks!


I am prob just stuck bleeding the system again. just wanted to check and see if this was similar to anything someone else may have dealt with.


thanks everyone!

[Hib Halverson]

If the Service ASR and ABS lights are coming on, codes are stored in the EBTCM.

Your scanner will not read them so you need to look at this article (http://www.corvetteactioncenter.com/tech/c4/abs/index.html) to see how to get them.

"Pull" the codes and report back.

[92whiteZ]

Thanks everyone.

Hib - will read your article and report back.

its strange to me that it is only under hard braking where the body pitches forward. still think i have air stuck somewhere in the system. the MC is full and clear.

[Hib Halverson]

My gut feeling is what's turning those lights on is unrelated to brake hydraulics.

I'd get the codes then diagnose per the Service Manual.

I'm going to guess there's a wires/connections problem somewhere.

[92whiteZ]

Ok. Finally got back and looked at the trouble codes. 77 ignition cycles ago it threw a code 71. 2 ignition cycles ago it threw a code 83.

71 is an internal malfunction of the EBTCM
83 is low brake fluid.

My m/c is 1/2 way full. Will top it off. The code 71 is obviously much more of a concern. I will say the lights only come on during heavy braking or acceleration as I believe the body movement uncovers the fluid sensor in the m/c. Hopefully topping off the m/c will take care of it. ..

Cleared all the codes. I am using a Tech 1a for reading them. How did I ever survive without one!? Definitely a "must have" item for diagnosis.

Any additional advice/thoughts?

[92whiteZ]

Oh and I did put dielectric grease in the spark plug boots just to check that off the list too.

[92whiteZ]

Looks to have been just slightly low fluid. Topped it off and put some miles on it. No lights. All appears to be well. Thx for all the advice everyone.