RCosh927

So what was the out come ?
They reset abs & trac system when battery was disconnected ?

Wayne B

I know this is an old post. However I need to know how to "reset" the ABS system. My experience was similar in that I had a low brake pedal going forward. In reverse the pedal was firm. The shop (Non Chevrolet Dealer)said they would bleed the brakes. They did, pedal still low. They changed the Master Cylinder. Pedal still low. A mechanic from another shop said that he needed to bleed the system with a Scan Tool. He did and the pedal was firm for about 30 days or 2500 miles. Then my wife did a panic stop and now the pedal is soft and low again. The shop does not know what caused it or what to do. Any direction other than taking to a Chevrolet Dealer would be appreciated.

RJ_RS_SS_350

Hi Wayne, to the forums!!

Apparently, running in gear, with the wheels off the ground, is what caused OP's problem. If you did not do the same, then you likely have a different problem. Did you check all the suggestions that were made in this thread?

Oldblue

I have done a reverse bleed in ABS brakes, the trick I believe was I bleed the brakes with the car running. Farest wheel first then the closer and so on.
The owner hasn't complained about any further issues since then, last May

http://www.brakebleeder.com/solution.../how-it-works/

Wayne B

Thank you for the responses. Yes, I did check all the responses. I did not jack up the car and spin the wheels. After a proper Scan Tool Bleed the brakes were perfect. Then after a panic stop whereby it is possible that one or both wheels tired to skid, the soft pedal came back. No lights or codes present.

donbrew

You can't "reset" the ABS, that would not fix your problem anyway. You might try disconnecting the negative post of the battery for 20-30 minutes, that will basically reboot all of the computers. You did not say what happened just before this started.

I was embarrassed to find the correct bleeding sequence is: RR,LF,LR,RF. Since the system is not split F/R, but diagonally. I have been doing it wrong all of these years!

Has anyone looked at the booster?

My 3,000 mile diagnosis is the rear brakes need adjusting or replacement.

No need for a GM dealer, just a good brake shop.

Wayne B

Don;

Thank you for your response. The system had a low/soft brake pedal when I got the vehicle. New front disc pads, adjusted the rear brakes. Brake Service shop then bled the brakes manually, then replaced the master cylinder and could not improve on the soft/low pedal. A technician from a neighboring shop told him that he needed to use his Scan Tool to bleed the brakes. He borrowed the tool and did a Scan Tool Brake Bleed and the pedal was high and firm. After one panic stop one month and 2500 miles later the soft/low pedal returned. The shop has no clue as to what to do now.

donbrew

Find a brake shop.

If the rear brakes are still good then the front calipers are frozen. The panic stop may have broken something in the rear or moved the calipers to a point where they stick.

aradmahogany

When I had both rear brake cylinders replaced on Gregg the shop gave him back with a DEAD brake pedal. They didn't adjust the rear shoes at all. After adjustment the pedal firmed up to normal, but overtime would loosen. I discovered they installed the adjustment wheels backwards. I fixed this, great pedal since. with the HHR drums, you have to make it about a 6 month habit to crawl under there and adjust the drums. I wouldn't advise going to a shop, because each shop tech that touches it will have an opinion on drum snugness. For instance, the tech that did mine after he gave the car back after readjusting stated it "makes him uncomfortable to tighten drums that much." When I got the car home after that visit I jacked him up and spun the wheel. slight drag with about 2 rotations of the wheel before stopping under its own weight using the index/thumb method. Works perfect for me, at least.

donbrew

If any tech in a shop looked up on the peg board behind the brake lathe and the shoe trimmer they would see the correct tool for adjusting drum brakes.

First you measure the I.D. of the drum, then use the other side to set the width of the shoes. The tool is usually preset for the proper clearance.