Hello!

I´ve got some problems with the abs on my -89. The "ANTI LOCK" light comes on as i turn on the ignition, and then stays that way. I can hear both the modular and the solenoid relay clicking. The solenoid relay clicks two times "ClickAClick" . As that happens the antilock light flashes. ???????

This is what i have done so far: Fuses are ok. Checked the relays and swiched the modularrelay with a new one. Checked the cabels and the wheelsensors, all four reads about 1000 ohms. I drove the car to a GM repairshop, but their computer would not comunicate with the abs controlmodule..
Any suggestions on what my next step would be?

Thanks in advance!

:seeya

 

That could be a big problem. I'd try another dealership or just jumper the ports yourself to see if you get anything.

BTW, welcome to the forum.

 

That is exactly what the dealership I went to told me. Then they told me they needed to replace the ABS brain which according to them costs around $1150. Definately take it to another dealership. You can get the ABS brain for your car for around $100 here or on EBAY. I have seen the pump and brain sold for $150 so just keep an eye out.

 

Thank you!

About the ECM: According to them, that was nothing unusual for corvette? Isn´t Corvette the only GM car equipped with Bosch absrelays and controlmodule?

 

Hi Chosen.

Yes, its about $1150
But i´m not so sure thats the problem.
have you replaced yours? and if so, is it working now?

 

Zeb,

Ive been having the same problems and I went to a Quick Align and Brakes and the guy printed out the entire manual diagnostic testing proceedures for our brakes. I dont have a scanner, but I can make copies and mail them to you if it will help. If you want a copy, IM me your addy and I'll mail it out tomorrow.

Oh and I bought an used Control Module and a Pump off ebay for $50+shipping. They are easy to find. The hard stuff to find are the sensors.


[Modified by VetteNoob, 6:13 PM 3/17/2004]

 

I can't find an abs wheel speed sensor for a 1987! Any ideas? :mad

 

'89 requires a special tool to interface with the module - some dealers don't have them and since you're in Sweden, you may be out of luck. You could try Contemporary Corvette for a used module - http://www.contemporarycorvette.com - (I think?).

 

No it did nothing for mine. The dealership told me that they couldn't communicate with mine, and that I would have to replace it before they could even do any further diagnostics. Typical GM dealerships approach, throw parts at it until you fix it. I bought one off EBAY for $100, put it in, and it didn't make a difference. To be honest I didn't do much of anything. I plugged the original ABS module back in, and kept driving. It just started working again after about 500 miles. I really think it was just from not being run for the last 5 years.

In no way, shape of form am I suggesting that the same will work for you (nothing), or that the ABS computer in your car isn't bad (might be), but DO NOT GIVE GM $1150 FOR A PART YOU CAN BUY FOR $100! Autozone has a ABS meter that you can hook up to your system and get codes. I would start with that, then check wheel speed sensors, fluid level, and THEN start tracing wires and thinking somethings wrong. IMHO, if the ABS pump cycles, the ABS computer is fine, but I could be wrong. If I am I'm sure someone will bring it up.
Also, check the GM service bulletins. There was something about the pump binding in some models, but don't know which ones.

 

That's probably why they couldn't communicate with it

 

Found this:

Flash Code Diagnosis

1986-91 Vehicles

The flash code diagnosis can only be used on 1986-91 vehicles to read ABS codes except for codes 41, 45, 55, 61, and 61. Those codes can only be read with the use of a Tech 1® or equivalent scan tool, as outlined later in this section.

On these vehicles, you can "flash" the ABS trouble codes through the SERVICE ABS indicator light on the dash panel as follows:

1.

Ground terminal "H" of the ALDL connector, then turn the ignition to the ON position. The flash code diagnostics will stay enabled as long as the terminal is grounded, serial data line communication has not been initialized and the vehicle speed is less than 4 mph.

Link to the page:
http://www1.autozone.com/servlet/UiB...3d80213ffc.jsp

I thought this wasn´t possible ?

 

I don't think so. Module doesn't interface with the ECM, there isn't any connection to the DLC, nor are there any trouble codes. The light is illuminated when the control module provides a ground. That happens when the vehicle starts or if the functional test fails after the vehicle gets rolling. The tester plugs into the module harness after it is disconnected and performs a sequence of tests with the results displayed in a text format. There are about a dozen or so troubleshooting charts in the Shop Manual and if you could get the module powered up, you could probably troubleshoot each one with a test light and DVM, but the ABS light isn't going to tell you anything. If the light is staying on after it's started, but before the functional test, you might suspect the module. If it comes on after the functional test, wheel sensor, pump & relay or the module.

 

Hrmmm.....

Didnt think that was possible, but I guess it couldnt hurt to try it.

 

Zeb,

Do a search for ABS posts with my username in them and you should find my previous long winded response that should help. I've had a LOT of experience diagnosing an early C4 ABS problem on my 88. I purchased the GM Training video for 86-90 ABS and also the the official GM Kent-Moore ABS test system. I can assure you that the Autozone article was written by someone who used those techniques on a 91, but NOT on an earlier version ABS C4. The 91 has a completely different controller than was used in 86-90, but the GM Dealer Guide lists the 91 ABS system parts in with the 86-90, so they probably "assumed" it was all the same. As the others have already mentioned, the 86-90 C4 ABS does not store codes or interact with the ECM so jumpering the ALDL for ABS codes is a waste of time on an 89.

You say that you tested the sensor resistance and all are at 1000 ohms which is correct for static testing. The ABS controller cycle tests the sensors and pump at 4~6 mph forward or reverse. In my previous posts I detail how to check the sensor gap voltages when moving, but you describe a fault prior to the car moving so it is my guess that it is an electrical problem and not a bad sensor gap voltage issue.

I would guess it is one of the 3 ABS relays, a bad diode, or a wiring short somewhere. Since you have already replaced a module relay, there are only 2 left to test/replace. The 3 ABS relays in an 89 are:
1636973 .... RELAY, ELEK CONT
14105967 ... RELAY, PRESS MOD VLV SOLENOID
14105968 ... RELAY, PRESS MOD VLV PUMP MTR => Replaced with GM part # 12513302

The 14105968 relay was replaced with a GM unit of different internal design. It is the first relay I would replace and then follow that with a new 1636973 unit. Forum member Chris at Superior Chevy 800-728-8267 can get all 3 for you at a major discount to the usual GM dealer price. Approx $35 each from Chrris, $54 each from dealer in US.

Wired to the ABS controller is a single external diode. It is usually covered in tape from the factory and if my late night memory is still good the diode is located on the feed wire to the ABS SYS light in the console tell-tale. If the diode goes bad, you will see a constant ABS light.

There is also an ABS accelerometer onder the AC control unit in the center of the instrument pane. If you pull out the carpeting on the pasenger side of the console you will see it under the AC controller unit. It has 2 wires going into it and is a bit of a pain to remove and replace. It is essentially a mercury switch which tells the ABS controller when the car is in a turn, so that the controller will know that the voltage difference between the outer wheel sensors and the inner sensors is due to the turn radius difference and not a skid condition. If this unit is bad, it could cause a fault light from statup. Most junkyards have several since they aren't that expensive new and don't fail that often.

Let us know how it turns out,
Mike

 

This can seems stupid, but worked for me.
These symptoms were the same I had with my 90. I repeat: same symptoms.
Solution ?
The level on brake fluid was a little low. I flushed the system and putted in new dot 3 oil to the max level.
No more light, no more problem.
I hope is the same for you!
-Beppe-