Replaced a failed brake hose (It got too close to the tire and got a hole in it)
Before I changed the hose I got the Brake Light, Service ASR and Service ABS light because the fluid got way low in the MC.

Put new fluid in the MC, bled all 4 brakes. I now have brakes but I'm concerned that I don't seem to be able to trigger the ABS. When I stop the pedal seems to get real hard after 1/2 travel and then continues.

Do I need to bleed the ABS? If so is there a way to do it without taking it to the dealer?

 

The '92, unlike later units, has a brake fluid prime pipe from the master cylinder reservoir to the ABS/ASR unit and bleed screw in the ABS/ASR unit behind the driver's seat.
The procedure in the shop manual calls for bleeding the ABS/ASR unit first and then the rest of the vehicle.

Tom Piper

 

Aha - my shop manuals should be here next week. Guess I'll have to tackle it when they get here.

Thanks for the info.

 

If the fluid is low in the ABS pump, you should still get a Service ABS light in the DIC. If the MC reservoir emptied, you may have to bench bleed the MC.

Whenever the car is started and you begin to drive, you should hear a buzzing noise behind your seat. This is a self-test the ABS does and pumps a small amount of fluid from the reservoir into the pump and then back to the reservoir. Do you hear this buzzing?? If you don't, that means the pump is not working but you should see the Service ABS light. Check the ABS fuse.

A hard pedal is usually indicative of a failing brake booster, but the pedal should be hard all the time and not a certain point.

In order to properly bleed the ABS pump, you have to use a GM Tech-1 scan tool with the brake system module. That allows the ABS pump to run continuously to get fluid from the MC. There is a bleed valve on the side of the ABS pump housing and it gets pretty messy when fluid starts coming out.

Because the DIC warning lights came on, codes were set in the EBCM and may have to be cleared in order for the ABS system to work again. The CCM can be used to clear the ABS/ASR codes.

With the ignition OFF, put a jumper wire in pins A and G in the ALDL (A is the far right hole on the top row, and G is the far left hole on the bottom row). You can use a paper clip for this.

1. Turn the ignition to ON but don't start the motor.
2. Press the Trip Reset button repeatedly to display "9.0" in the trip monitor area of the speedo cluster.
3. Press the Trip Reset button twice to change the display to "9.7".
4. Hold down the ENG/MET button until " - - - " displays in place of the numbers.
5. Turn the ignition to OFF and remove the jumper.

 

No ABS Service light

Thats funny, I've never heard the ABS pump come on like I used to hear in my 88. I'll check the fuse tonight.

I'll do this this weekend.

I know a constantly hard pedal is MC related, but this doesn't get hard until after the pedal travels some and then moves again. I wonder where I can borrow the Tech-1 tool. Or is it important enough to break down and buy one?

Looking on eBay I found these - are they what I need?

Tech-1 scanner
Adapters

 

The Tech-1 is what the GM Service Techs use to do diagnostics. If that's a REAL GM Tech-1 it should be going for a whole lot more than the current $51 bid.

The fuse could be blown but it's always possible that the ABS unit itself is toast. They are expensive! A friend is trying to get a line on an ABS pump for his 90 ZR1 and the GM list price is $1320

GMPartsDirect has one for half that price but they want $180 shipping (and the @^*@!% thing weighs about 4 pounds and is about 6" on all sides).

 

The GM Techline Tech 1 scan tool will usually go for around $300.00. The first link did not say anything about cartridges. The Tech1 is like a video game unit, you buy the main box and then you buy different cartridges for your application. They have a Mass Storage Cartridge that can be loaded with all GM OBD1 data, these can bring $100.00 on E-Bay.

 

The Vetronix MasterTech is a glorified Tech-1A.
They use the same identical sofware cartridges.

The MasterTech has more lines of display and can be used like an oscilloscope.

For both the Tech-1A and MasterTech, for the ABS, you need either the "mass storage cartridge" or the "chassis cartridge."


Tom Piper

 

I think you need to double-check the GM shop manuals on how to bleed the brakes.
If I remember correctly, on the '92, you don't need the scan-tool to bleed the ABS/ASR unit because of the prime pipe and bleeder screw on the unit.
I don't know what year the change was first made, but later C4 vehicles did not have the prime pipe, I know the '96 doesn't have it. So, I don't know the bleeding procedure on the '96.

Tom Piper

 

For a replacement pump has he tried vette2vette (used corvette part supplier)?

I hope mines not toast - yeecchhh.