calling all Tech guys (ABS stuff) [Archive] - Corvette Forum : DigitalCorvettes.com Corvette Forums

: calling all Tech guys (ABS stuff)


Roadrunr
08-09-2004, 01:08 PM
Hello Friends,

I have a ABS problem, ABS light is on and I am looking for tips or sites with info on C4 1988 ABS, the use of the J35890 ABS tester and how to take out a ABS pump.

Any help is welcome,

TIA Pim

CorvetteInfo
08-09-2004, 01:38 PM
While I dig up the threads, can we have the CODE you are throwing please?

TIA
D

Roadrunr
08-09-2004, 03:05 PM
Originally posted by c5d
While I dig up the threads, can we have the CODE you are throwing please?

TIA
D

ABS will not set a code on a 88 :bang

CorvetteInfo
08-09-2004, 08:18 PM
Originally posted by Roadrunr
ABS will not set a code on a 88 :bang

Then can you confirm you have no SES light and/or your ECM has not stored a Code 24 (Vehicle Speed Sensor) fault?

I can provide '90 info, and I note ACDelco Part#14103343 is for a '88 Corvette, electronic brake control module (ECBM), which should be readable (?), and (I thought) throw a number of CODES related to the ABS, as in the '90.

Perhaps, let's clear this point of confusion, before we start on a full replacement.

Anyone with a '88 ever have ABS CODES??? Or does everyone except me know they don't ??? :huh:

TIA
D

Roadrunr
08-09-2004, 10:36 PM
Originally posted by c5d
Then can you confirm you have no SES light and/or your ECM has not stored a Code 24 (Vehicle Speed Sensor) fault?

I can provide '90 info, and I note ACDelco Part#14103343 is for a '88 Corvette, electronic brake control module (ECBM), which should be readable (?), and (I thought) throw a number of CODES related to the ABS, as in the '90.

Perhaps, let's clear this point of confusion, before we start on a full replacement.

Anyone with a '88 ever have ABS CODES??? Or does everyone except me know they don't ??? :huh:

TIA
D

That's correct D, no SES light, just the ABS light

Pim

-=Jeff=-
08-10-2004, 03:58 PM
Originally posted by c5d
Then can you confirm you have no SES light and/or your ECM has not stored a Code 24 (Vehicle Speed Sensor) fault?

I can provide '90 info, and I note ACDelco Part#14103343 is for a '88 Corvette, electronic brake control module (ECBM), which should be readable (?), and (I thought) throw a number of CODES related to the ABS, as in the '90.

Perhaps, let's clear this point of confusion, before we start on a full replacement.

Anyone with a '88 ever have ABS CODES??? Or does everyone except me know they don't ??? :huh:

TIA
D

D,

90 was the first year that the EBCM (ABS ECM) was connected to the ALDL Line.

89-older did not have that. there is a way to check the EBCM for errors in the older cars, I am just not sure how

CorvetteInfo
08-10-2004, 04:57 PM
ABS

Follow cautions on/around the SIR systems.
Certain ABS components are not designed to be serviced.
Always reinstall fasteners at the same location removed from. Replace with exact part or of equal or greater strength. Follow non-use, locking compund, and torque call outs.

General Description
The ECBM monitors performance, logic and circuitry, to determine malfunctions and set CODES.

Most ABS self-diagnostics are performed by the ABS Controller after 1.7mph.

Built-In-Test Equipment (BITE) is performed once each IGN cycle at 3-11mph, cycling each solenoid valve and pump motor as follows:

IGN ON the ECBM grounds and activates solenoid relay.
3-11mph, the ECBM test solenoid valves & hydraulic modulator pump (usually can be heard).
If the pump or solenoid fails, the ABS is disabled, CODE set, and SERVICE ABS, illuminates.

When the EBCm receives any Wheel Speed Sensor (WSS) signal, it checks WSS output. If any WSS signal is missing, ABS is disabled, CODE set, with SERVICE ABS lamp.

On vehicle movement, the ECBM continuously monitors itself and:

Modulator Valves
WSS
Wiring Harness and relays
BAT voltage

If BAT voltage drops below 9v, ABS is disabled and SERVICE ABS lamp illuminates.

Each malfunction type has an associated fault CODE, which is a two digit number flashed (for '90) over the SERVICE ABS lamp in the DIC.

Fault CODES involving the solenoid valves and pump motor cannot be read at the DIC (the SERVICE ABS reamins ON) and require the Tech 1 Diagnostic Computer to retrieve CODES.

While the SERVICE ABS is ON, only normal power brakes operate (no ABS during diagnostics or driving).

Prelim Diagnostic Checks
Before using CODE diagnostic charts, CHECK:
STOP/HAZ, BRAKE, SIR, & CLUSTER fuses.
Fuseable link "J"
Pump Motor, ECBM, and Solenoid RELAYS are firmly seated.
ECBM connector is properly mated.
GND System

[CSM, 1990, 5E1-50]

CorvetteInfo
08-10-2004, 05:23 PM
Originally posted by Roadrunr
... the use of the J35890 ABS tester and how to take out a ABS pump.

The '90 uses the J34029-A: High Impedance Digital Multimeter.
94-00101-A: Tech 1 Diagnostic Computer.
J 35592 Pinout Box

Is your J35890 ABS tester any of the above?

Testing the ABS Pump & Relay

Once the pump motor realyis grounded by the ECBM, it provides B+ to operate the pump. A CODE 61 sets if 12v is at the pump without relay activation, or if 12v is not present after relay activation within 60 milliseconds.

To check for Motor or Relay fault:
Correct Relay resistance
Stuck relay
OPEN in the Hydraulic Modulator circuit
GND
Correct Pump Motor resistance

IGN OFF
Remove Modulator cover and Motor Relay (4-pin)
Measure resistance between Motor Relay Pins 85 & 86. Is it 45-55 OHMS?

NO: Replace Motor
YES: Measure bet Valve Relay pins 30 & 87. Continuity: Replace Motor. No Continuity: Disconnect (DIS) connector (CON) from Hydraulic Modulator. Measure resistance on Modulator between:

Modulator pin 10 & Motor Relay CON PIN 87
Modulator pin 8 & Motor Relay CON PIN 86
Modulator pin 12 & Motor Relay CON PIN 85
Modulator pin 9 & Motor Relay CON PIN 30

More than 2 OHMS at any step: Replace Hydraulic Modulator Assy.

0-2 OHMS at each step:
Measure resistance bet Modulator GND wire CON on Modulator Pump and a good chassis GND. Is it at 0-2 OHMS? NO: Replace/repair GND wire. YES: DIS PUMP Motor CON on Modulator. Measure resistance bet PUMP Motor & GND. 3.5-4.5 OHMS? NO: Replace Hydraulic Modulator Assy. YES: continue diagnosis (6-13).

[CSM, 1990, 5E1-30]

Do you wish to continue?

Patrick
08-10-2004, 05:27 PM
Originally posted by c5d
Do you wish to continue? [/B]

:laughing: :rolling: "Press any key for more C5D!"

CorvetteInfo
08-10-2004, 05:53 PM
This test continues from above to check:

BAT Voltage available to the Pump Motor Relay.
Short to BAT in Relay feed circuit.
Potential OPEN or Short to GND in CKT 998.
Open, Short to B+, or Short to GND in CKT 913.
If CKT 998 problem is due to circuit itself or faulty ECBM.
Open, Short to B+, or Short to GND in CKT 985.

Reinstall Motor Relay on Modulator
Measure voltage bet Modulator CON pin 12 & GND. Approx. 12v? NO: Repair OPEN in CKT 2. YES:

IGN OFF
Measure voltage bet Modulator pin 10 & GND. Approx. 12v? YES: Repair SHORT to voltage in CKT 998. NO:

IGN ON
Measure voltage bet Modulator pin 10 & GND. Approx. 12v?

NO:
IGN OFF
Install J 35592 Pinout Box
Measure resistance bet Pinout Box pin 17 & 20. Continuity: Repair Short to GND in CKT 998. OPEN CIRCUIT: Measure resistance bet Pinout Box pin 17 & Modulator CON pin 10. 0-2 OHMS: Replace EBCM. OUTSIDE 2 OHMS: Repair OPEN in CKT 998.

YES:
IGN OFF
Install J 35592 Pinout Box
Measure resistance bet Pinout Box pin 28 & 20. Continuity: Repair Short to GND in CKT 913. OPEN CIRCUIT: Measure resistance bet Pinout Box pin 28 & Modulator CON pin 11. OUTSIDE 2 OHMS: Repair CKT 913. 0-2 OHMS: Measure voltage bet Pinout Box pin 28 & GND. Approx 12v? YES: Repair Short to voltage in CKT 913. NO: Measure resistance bet Pinout Box pin 14 & 20. Continuity: Repair Short to GND in CKT 985. OPEN CIRCUIT: Measure resistance bet Pinout Box pin 14 & Modulator CON pin 9. OUTSIDE 2 OHMS: Repair OPEN in CKT 985. 0-2 OHMS: Measure voltage bet Pinout Box pin 14 & GND. Approx 12v? YES: Repair Short to voltage in CKT 985. NO: Replace ECBM. Replace Hydraulic Modulator.

CorvetteInfo
08-10-2004, 07:45 PM
Originally posted by Roadrunr
... the use of the J35890 ABS tester...

In 1986 Corvette introduced ABS Bosch II as standard equipment. 1987 through 1992 GM was using the Bosch III ABS system. By 1998, Corvette was running Bosch 5.3.

On the 5.3, the EBTCM or BPMV can both be replaced separately, but neither component is considered serviceable. So if an ABS solenoid valve, the pump or a relay fails, the whole BPMV assembly must be replaced.

http://www.babcox.com/editorial/bf/elements/20136b.gif

Here's a general guide for the Bosch III NOT CORVETTE SPECIFIC:

Overview

The ABS system consists of:
Electronic Brake Control Module (EBCM)
A hydraulic pump
ABS unit
Wheel sensors
About 1990, the Traction Control was integrated with the ABS system.
ABS pump relay
Stop light switch.

The ABS unit has several major components:
Sensor Block
Accumulator
Pressure Control Switch
Fluid Reservoir
Valve Body
Hydraulic Unit.

SYS Operation

Each time the car is started, messages and warning lights are tested. With IGN ON, 12v is realyed to the ABS pump. The pump pressurizes the hydraulic assist to operate the ABS system. The EBCM monitors pressure via the Pressure Control Switch, and signals (by relay) the pump ON/OFF to control pressure.

The accumulator stores pressurized fluid to assist braking. When the brake pedal is applied, the EBCM operates/monitors the system using various sensors from around the car. Under normal braking, the pump runs for a short time.

ABS braking occurs only when a wheel starts to skid. The wheel sensor detects the skid and signals the EBCM. The ABS opens the corresponding wheel valve to allow the wheel to roll. Then the wheel valve closes and braking is reapplied.

ABS Failure

There are four general categories of failure:

Loss of power assist.
Due to the ABS pump's not running, or insufficient pump pressure to run the ABS system.

Symptoms are a hard pedal with decreased stopping ability.

Loss of fluid as a result of a blown seal or ruptured brake line.
The pedal travel increases and/or goes to the floor, with corresponding fluid leakage under the car.

Error messages/warning lights illuminate with normal braking ability.

Error messages/warning lights illuminate with abnormal braking ability (reduced or inconsistent braking).

Simple Troubleshooting[b]
ABS PUMP AND ACCUMULATOR

To determine if the ABS pump and accumulator are functioning within normal limits:

When the key is turned ON, the pump should run long enough to repressurize the system, and then shut off.

Locate the pump:
Turn the key ON (the pump may/may not run).
Completely depressurize the ABS system by turning the IGN OFF, then pump and release the brake pedal firmly at least 25 times. Normally, the pedal will go to the floor when you first starting pressing it. After a number of applications, it will come off the floor, and feel like you are building pressure. This is the point at which the system is depressurized.

Once the SYS is depressurized:
Using a watch with a second hand, turn IGN ON, without starting the car. The ABS pump should run 25-30 seconds, before turning OFF.

Depressurize the SYS by turning the key OFF, then count the number of times the brake pedal is pressed before you experience the change in pedal pressure (stops going all the way to the floor). [b]A good accumulator should store 15 to 20 pumps before it is depressurized.

Further evaluation requires ABS pump to run for the above test. If the pump fails to run, the cause must be found and corrected before any further analysis can be performed.

HOW TO REPLACE THE ACCUMULATOR

Accumulators were originally designed as throwaways, but can be modified to be rechargeable. Recharged accumulators are available for much less than the price of a new accumulator. With new seals, they will give the same service as a brand new one, at less than half the price.

Tools you will need:
¼" drive ratchet, w/ ¼" drive 3" extension
¼" drive THIN WALL ¼" hex socket
#30 Torx bit (comes with magnetic Torx screwdriver with multiple bits)

If bleeding brakes: clear hose, glass jar, new brake fluid, DOT 3, 4, 5.1 only. DO NOT use SYNTHETIC brake fluid, it is not compatible with ABS.

To replace:
Key OFF
Depress brake pedal 25 times to completely depressurize system.

There are two Torx screws holding accumulator to hydraulic unit from up underneath.

Check size of Torx bit in screw head for proper fit. Assemble ratchet handle, 3" extension, ¼" socket, and #30 Torx bit to remove both screws. Be careful not to drop screws. Once the screws have started to come loose, ratchet can be removed, and screws turned out by gripping the end of the extension and turning them out much like a screwdriver. Be careful not to strip the screw heads. Keep the ratchet as straight as possible into the Torx head.

Wipe off plate on top of hydraulic unit after old accumulator is removed. Put new O-ring into port on bottom of recharged accumulator. Reinstall two screws and tighten. Very little brake fluid is lost. Turn key ON, and check for leaks. Time the length of time pump runs before it shuts off. It should be around 25 to 30 seconds.

To bleed hydraulic unit, which is a good idea, shut key OFF and depressurize system by pumping brake pedal 25 times.

Attach clear hose to bleeder fitting on passenger side of hydraulic unit. Take a glass jar. Add about 1" of new brake fluid to jar. Submerge end of clear hose in brake fluid in jar. Open bleeder screw, turn key ON, let fluid run until no bubbles are present, then shut off bleeder. Turn key OFF. Add brake fluid as necessary to full line on reservoir.

HOW TO REPLACE THE BOSCH III ABS SYSTEM
General description/overview ONLY:

Depressurize the SYS by depressing the brake pedal 25 times with the key OFF.
Disconnect BAT - TERMINAL
Disconnect the electrical connector to the ABS pump.
With a jar, pull the hose off the bottom of the brake fluid reservoir where it feeds the ABS pump.
Drain the reservoir drain into the jar.
Disconnect all brake lines.
Disconnect the two hoses to and from the ABS pump. Disconnect the electrical connector that goes to the top of the sensor block.
Disconnect the connector to the brake fluid reservoir.

If you have traction control, there will be more lines, and a traction control valve assembly. That stays in place and is reused. With traction control, there would also be an adapter on the bleeder screw port that must be reused from your old unit. Just make sure you reuse anything that’s different.

Remove/replace the ASSEMBLY.

When reattaching the lines, be very careful not to cross thread anything. Work with fingers only until the connection is started straight.

Go around all connections before powering up the system to make sure they are all tight. Make sure you use only DOT 3, 4, or 5.1 brake fluid to refill the systems. The seals in ABS systems are not compatible with silicone (synthetic) brake fluid.

Reconnect electrical wiring connectors and BAT GND.

To manually bleed (without a power bleeder or vacuum bleeder) the system after reinstallation:

First the ABS pump gets bled, key ON, until bubbles are gone. A clear hose gets attached to the pump bleeder screw, the end of this hose submerged in a jar with about an inch of clean brake fluid in the bottom. Open the bleeder screw on the pump, and let it run until it clears up. About 30 seconds at a time is all you should let the pump run. Let it rest for a minute, then another 30 seconds, etc. Generally three cycles of this will be enough. Keep the reservoir full, within 1/4 inch of the full line.

Next you bleed through the bleeder screw on the master cylinder. Again, have a clear hose on the bleeder, end submerged into a glass jar with clear brake fluid. Open the bleeder screw. Turn the key on, and let it run until fluid is clear of bubbles. 30 seconds on cycle, then rest.

With two people, turn the key OFF. The order of wheels is RR, LF, LR, RF. Attach clear hose to bleeder, end submerged in glass jar with 1" of brake fluid in it. Have an assistant pump pedal a few times, then hold, and open bleeder screw until flow stops. Tighten screw before pedal is released. Repeat as needed until fluid is clear and there are no more bubbles. Keep an eye on the fluid level in the reservoir.

C'ya
D

Patrick
08-10-2004, 07:48 PM
For the love of God, that is the most incredible tech reply ever!

:surprised

:thud:

moore_rb
08-10-2004, 10:46 PM
Zzzzzzzzzzzzzzzzzzzzzzz..........

Zzzz, Huh?, Wha? (wipes sleep out of eyes)


Oh, Sorry, D. I thought I heard you say somethin about ABS............


Zzzzzzzzzzzzzzzzzzzzzzzzzzz............. ....

Roadrunr
08-10-2004, 11:23 PM
Good morning D,

Hold on there Bro :D I need to read all of this and try to understand it all but I first have to go to work.

The J35890 tester I have on the way from the US (Ebay buy) is the tester that is the correct one for my 88, it's in the GM manual (big red bible)

After I have read it all I try to write a response.

off to work now,

Thanks, Pim

Roadrunr
08-14-2004, 07:09 AM
Many thanks D, man you are good :thumbsup:

The tester I have on the way is not the same as you talk about, and the Bosch III system is not what I have, but your info helps me to understand and all helps.

Thanks,

CorvetteInfo
08-14-2004, 01:25 PM
Originally posted by Roadrunr
... the Bosch III system is not what I have...

What SYS do you have, and is that stock? :huh:

TIA
D

Roadrunr
08-14-2004, 02:25 PM
Originally posted by c5d
What SYS do you have, and is that stock? :huh:

TIA
D

yes totaly stock, may be your are right about the Bosch III system but this is wat it looks like

http://i6.ebayimg.com/02/i/01/4b/16/f4_1.JPG

and this is the tester I have on the way

http://i12.ebayimg.com/02/i/02/38/22/da_1_b.JPG
http://i21.ebayimg.com/02/i/02/37/d6/9c_1.JPG

I hope it will be in soon so I can start testing.

Geetz, Pim

G Peterkin
08-15-2004, 10:22 AM
Roadrunr- Just want you to know that on Ebay there is an ABS manual for 1987& 1988 corvettes. Current bid is $9.99. If you want to check it out go to Ebay Autos and Parts go to manuals and literature ( in the sub menu). Then put in 1988 corvette. There is a little more than a day left on the bidding.

Roadrunr
08-15-2004, 11:15 AM
Originally posted by G Peterkin
Roadrunr- Just want you to know that on Ebay there is an ABS manual for 1987& 1988 corvettes. Current bid is $9.99. If you want to check it out go to Ebay Autos and Parts go to manuals and literature ( in the sub menu). Then put in 1988 corvette. There is a little more than a day left on the bidding.

Thank you much G, but do you see the one bidder on this item :D

Pim is my first name and NL stands for Netherlands, so pim-nl is me :smokin:

But this is what digital corvettes makes a great place to be, people you don't even know help you.
You guys are the best .

:cheers: :thumbsup: :thumbsup: :thumbsup:

Thanks, Pim (nl) :laughing: :partyon: