C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Anti-Lock module or pump

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Old Jun 24, 2013 | 12:56 PM
  #1  
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Default Anti-Lock module or pump

I have an anti-lock code on my '87..how can I diagnose the module
or the pump..all else checks out.
Bon Air
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Old Jun 24, 2013 | 02:17 PM
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Originally Posted by Bon Air
I have an anti-lock code on my '87..how can I diagnose the module
or the pump..all else checks out.
Bon Air
What code are you chasing?

What are the symptoms?

Define the "All Else" that check's out.
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Old Jun 24, 2013 | 05:05 PM
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Require more information.
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Old Jun 24, 2013 | 08:18 PM
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Default Anti-lock,'87

Let me qualify that post; the ABS is inoperable and I have the dash light
signaling anti-lock trouble. My scanner is too new to give an exact code
but my mechanic checked the wheel sensors, reluctor rings but stopped
at the control module (not having any special tools). I understand Bosch
made the module and the trail ends there. I would like to find the actual
cause before replacing parts; used module is about $250 +-.
Bon Air
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Old Jun 24, 2013 | 08:38 PM
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I guess it is safe to assume you don't have a Factory Service Manual. It is hard to do much troubleshooting without one. Even without a scan tool, you can troubleshoot quite a bit with a multimeter *IF* you have a schematic.

Without an FSM, a good place to start is to check all fuses.
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Old Jun 25, 2013 | 12:50 AM
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Bon air read this article it will get you going on trouble shooting your system. http://www.corvettefever.com/howto/19239/ This article will help you TS the module relays which are normally at fault.
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Old Jun 25, 2013 | 10:08 AM
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Thanks for the reply-I read the article, but where would I look for the relays mentioned--
GM is a dead end. I would like to cover everything before I open it up.
thanks,
Bon Air
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Old Jun 25, 2013 | 10:37 AM
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Originally Posted by Bon Air
...but where would I look for the relays mentioned--
Are you asking where on the car the relays are located, or where can you obtain a replacement? If you Google "87 Corvette ABS relay" you will find answers to both questions.

Originally Posted by Bon Air
...I read the article, . I would like to cover everything before I open it up...
Did you check all fuses as previously suggested? I read the article too, and the troubleshooting sequence seemed a bit bass ackwards to me. They run you through troubleshooting the relays and THEN have you check for power. First things first. Check your fuses. A blown pump motor fuse means no pump motor, which causes a failed power on self test, which triggers the ABS IDIOT light.

Last edited by Just BOB; Jun 26, 2013 at 10:12 AM.
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Old Jun 25, 2013 | 08:12 PM
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Originally Posted by Bon Air
Thanks for the reply-I read the article, but where would I look for the relays mentioned--
GM is a dead end. I would like to cover everything before I open it up.
thanks,
Bon Air
Bon: I have some good used relays available if you wind up determining that they are the cause of your ABS light. I just did a bunch of troubleshooting on my '86, and it turned out to be a bad connection at one of the sensors......

Regards, Chris
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Old Jun 25, 2013 | 08:26 PM
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Hey Chris/BOB:
Thanks again for the help, I just checked all fuses, and with limited knowledge, tested the voltage to all the relays, removed them and listened for any loose rattle and re-checked
all the ground connections. Sometime you just live right; when I started it for a test the
trouble light was OUT. Amen
Bon Air
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Old Jun 26, 2013 | 08:06 AM
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Originally Posted by Bon Air
Hey Chris/BOB:
Thanks again for the help, I just checked all fuses, and with limited knowledge, tested the voltage to all the relays, removed them and listened for any loose rattle and re-checked
all the ground connections. Sometime you just live right; when I started it for a test the
trouble light was OUT. Amen
Bon Air
Bon: Awesome; it's always nice when you find a loose conenction or whatever and it clears things right up..........
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Old Jun 30, 2013 | 01:30 PM
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Default Chris 1

Light still on-Did you say you had some good used relays?
Seems like the best way to go--Let me know how we can make a deal.
Bon Air
('87 Anti-Lock-light on)
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Old Jul 3, 2013 | 02:19 PM
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Originally Posted by Bon Air
Light still on-Did you say you had some good used relays?
Seems like the best way to go--Let me know how we can make a deal.
Bon Air
('87 Anti-Lock-light on)
Bon: I have 5 or 6 of the Control Module Relays, either part #: 14084083, or 1636973; both operate the same, however one has a little bit of a shroud on it where the harness connects to it. Both have long since been discontinued with no one in the aftermaket reproducing them. Not sure if you want to try one or not before actually testing yours first. I wound up paying top dollar for them, $40 each, since the guy I got them from knew what he had, and how tough they are to find. If you want one, I'll give it to you for my cost plus just a couple of bucks to cover the shipping cost. Let me know when you get a moment.....

Regards, Chris
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Old Jul 3, 2013 | 07:22 PM
  #14  
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Chris:
I sent something earlier but it was through my phone (I don't trust the connection).
I tested the relay #1636973, the larger one with the connector, each wire reads 11volts
+- and the ground reads zero. There two smaller relays on top of the pump but they simply
plug in, one is a RY-304, the other is silver colored..I assume you just swap in a good one
just to check. Do you also have these smaller plug-ins?
Bon Air (by the way BonAir is the golf club where I belong..easy to remember)
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Old Jul 3, 2013 | 09:17 PM
  #15  
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Originally Posted by Bon Air
Chris:
I sent something earlier but it was through my phone (I don't trust the connection).
I tested the relay #1636973, the larger one with the connector, each wire reads 11volts
+- and the ground reads zero. There two smaller relays on top of the pump but they simply
plug in, one is a RY-304, the other is silver colored..I assume you just swap in a good one
just to check. Do you also have these smaller plug-ins?
Bon Air (by the way BonAir is the golf club where I belong..easy to remember)
Bon: From all the reading I have done, and my personal experience, 95% of the time it's either the Control Module Relay, or 1 of the ABS wheel sensors, with more times it being a wheel sensor if the ABS light is off when you first start the car, and then comes on after you reach 6 or 7 mph. Rarely is it one of those other 2 relays, the solenoid relay, or the pump motor relay. According to the manual, with the key in the "Run" position, and the wiring connector disconnected from the relay, you should have battery voltage between 30 (orange and black) and ground, battery voltage between 15 (pink and black) and ground, and battery voltage between 15 (pink and black) and 31 (black). If those check out, then the voltages getting to the relay are correct, and it eliminates the wiring portion. Next, on the wiring harness side, if you take a jumper wire and jump pins 87 to 30, the pump should run. Try these tests first and let me know how you make out.......
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