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ABS codes, is my EBCM dead?

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
A few weeks ago the "service abs" light lit up on the DIC in my 90 Corvette. I have checked the fault codes several times and have found several codes, they are:

Code 31 (right rear sensor)
Code 25 (left front sensor)
Code 61 (relay)
Code 63 (relay)
Code 71 (EBCM error)

At first I only had the code 31 and code 25 and the right rear sensor showed high resistance so I replaced this sensor though that code still shows.
I couldn't believe that two sensors could fail at the same time so I started to check the wiring and as far as I could measure there were no shorts in the wires to the sensors (checked resistance at the sensors and at the connector in the compartment behind the seat and the readings were within limits.

The codes 61 and 63 have disappeared but the 31 and 25 are always present. The 71 has only appeared today. I have a feeling that this is the one that tells the true story - that my brake ECM (EBCM) is shot!

Has anyone experienced similar problems. Is the multitude of codes I'm seeing likely to be due to the EBCM going AWOL?

Anyone have any idea what an EBCM costs (not cheap probably)
I don't mind replacing it if that's definitely the problem.

Thanks fellow Corvette people.

See www.mm-2000.co.uk/corvette/
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
I'd replace the relay first

Instead of the whole E thing-a-mac-bobby


Looking in book!

Be back


Vig!
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Consider the following

The EBTCM Could have a bad ground it self!

1) Remove all the ABS wheel sensors and verify the wiring makes it from point to point.

2) Verify the GROUND for the ABS computer.


Considering your in the UK and the climate...

I would re check your electrical connections first!



Vig!
 

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
ABS EBCM

I have checked the ground connector, that seems OK and it felt secure where it is attached to the modulator (I had to do that last part by feel as it is hard [impossible?] to see with the modulator in place.

I no longer get the fault codes for the relays although previously I had 2 relay codes (!!!???)

The resistance at the white connector between sensor wires is tha same as at the sensors. I was presuming from this that the wiring is continuous and that there are no shorts. I have looked at the contacts on all the connectors on the modulator/ EBCM and all looks OK.

One thing I haven't been able to do is remove that huge connector to the EBCM itself. I guess it's possible that a pin or two might not be making contact (clutching at straws here!)

I've had quite a few electrical faults with this car though they've all been down to loose connections or something similarly trivial. I know the solution to this ABS thing is out there somewhere!
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
OK

remove the big connector & clean it!

We will proceede from there.


Vig!
 

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
ABS fault codes

Vig, I've just taken off the big connector. The pins on the EBCM look clean as do the contacts in the connector. I sprayed some WD40 into the connector but the codes persist!

The codes I get all the time now are:

31 right rear sensor
71 EBCM internal fault
25 Left front sensor

However I don't know which are current and which are history. Rabbit suggested a procedure to clear codes but I couldn't get it to work. I'm pretty sure the code 71 is current because that is the most recent.

I wonder if you or anyone else could answer this question:

The wires I have identified as leading to the sensors (connected to the white connector in the ABS compartment) are:

A pair of green wires
A pair of red wires
A pair of yellow wires
A pair of white wires

Does anyone know which colour wires lead to which sensor?

Thanks, Malc.
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
EEEKKKKK!

WD-40 that's OIL

Oil is an insulator!!!!
You are betting the mechanical contact between connectors is 100%

You need a contact cleaner!!!!!!!

When you pull error codes
the H is history
the C is current


The relay is special...get that from the dealer

I do not have a 90 book here

for an 93

( on the smaller connector )
C) Light blue LFW to pin 51 on EBCM
B) Yellow to LFW to pin 49 on EBCM

D) Dark Green to RFW to pin 47 on ECBM
E) Tan to RFW to pin 46 on ECBM

F) Light Grn to LRW to pin 45 on ECBM(RED)
G) Light Grn to LRW to pin 44 on ECBM(BLK)

H) White to RRW to pin 43 on ECBM (BRN)
J) White to RRW to pin 42 on ECBM (WHT)

LFW= Left front wheel
RFW= Right front
LRW= Left rear wheel
RRW=Right rear wheel
 

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
WD40

Sorry Vigman, I'll get the right stuff (contact cleaner) and do it again! I'll also try and see if each contact is real tight.

When I pull codes I only get the numbers, there's no C or H prefix. I'm using a tool (Gordon Killebrew's manual and shorting plugs) and reading the codes in the DIC.

I know that on a later car (92 or 93 on?) it's possible to read the codes disp[layed in the speedo area but I don't think that's possible on a 90 (?)

Malc.
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Wishing I had a 90 shop manual

I hate stupid things......

Oh well I would hate fo you to replace the ABS computer only to find that wasn't the problem!


Vig!
 

Rabbit

Well-known member
Joined
Dec 19, 2001
Messages
956
Location
sonoma ca usa
Corvette
2004 C5 coupe, MSGM & 2014 Cad SRX Crystal red
I don't know if this pertains as I am perusing the 95 manual. It seems that a code 71 will be set by a bad fuse on the underhood fuse block #1. Fuse #3 abs/asr ecu. For whats its worth.....:confused :confused :s
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
For a 93

It's pretty plain

Get a 71

Wiggle the wires
If that doesnt cure it
Replace it.


Youve replaced the ABS fuse correct, and verified power is at the fuse block?


Looking BAD at this point!


Vig!
 

malc350

Well-known member
Joined
Jul 6, 2002
Messages
337
Location
Essex, UK
Corvette
1996 LT-4 Z51 CE
ABS EBCM

I'll check the fuse and verify power at the fuse block. I'll also get some contact cleaner but I've already looked up the cost of a new EBCM (holy #*!!#~+*!!! batman, looks like $400-$500) and prepared myself for the worst!
 

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