C4 ABS lateral accelerometer - alternate options?

[jklumpp]

Hi All,
I'm new to the forums, but hoping the brains trust on here might have the expertise to help me out.
I brought my first corvette just over 12 months ago (a 1991 C4), and have had an ongoing problem with the ABS.
The 'Service ABS' light was on when I brought the car. My mechanic diagnosed the problems and we ended up replacing the ECU, Pump & Lateral accelerometer sensor.
With limited parts available in Australia of course I had to source the parts from US salvage yards. After the first faulty ECU, I ended up buying 2 of everything I needed from different suppliers, so that I had an alteranate should anything turn out to be faulty, so that I didn't have to wait another 2 weeks to receive parts....
Anyway, shortly after getting it all up & running, we had the Lateral Accelerometer (LA) throw another fault code, and we swapped it out with the 2nd sensor and all was good for a few weeks.
The that LA failed as well...
The Auto electrician has pulled all 3 sensors apart (original & 2 replacements), and all have failed in different ways, so we don't think it's being caused by something else in my system - just appearrs to be bad luck & 26 year old electronics....

I'm hoping to find another solution, other than buying more second hand sensors & hoping to find a good one.
Bosch have been no help, noting only that they discontinued manufacture of these parts in 1993! (as soon as they were no longer being installed in new cars!)
No other specs or details appear to be available to help us try & find an alternate.

Has anyone else been through this and found a solution, or does anyone have any suggestions that might assist?

The rego inspector refused to pass the car with the ABS warning light on, so I'm without a corvette until I can get this resolved!

FYI, the part numbers are:
Bosch P/N: 0-265-005-101
GM P/N: 1009602

[bfit]

There is a member who will see this in due course who will most likely be ale to give you some ideas.
but first question  Is the car still LHD.
bfit

[jklumpp]

No, the car has been RHD converted.... one of the problems my mechanic found when resolving the issues was that the LA had been installed backwards in the conversion!!!
That issue has of course been rectified now...

[sirfixalot]

SR Performance Arncliffe Club sponsor would be a good starting point

[toyvet]

SR performance--15 argyle st Wolli creek - call Steve Sharkey on 0439901560 👍👍

[Vettech]

I've got an 87, and I must admit, I've never had a code or any issues.

We are talking the unit screwed to the trans hump just in front of the shifter arent we. Covered in carpet, ac and radios etc etc.

Having typed the above and then going surfing, I now see plenty of people on the web with issues.

Because LA's started back in 84, they were rudimentary devices, now years later they have amplfiers, pizo's etc etc and are micro small.

So being a person who loves to pull things apart and see how they work, I'd love see inside the unit
The basic C4/87 electrical supp book, shows two switches in line, short or open, two wires, whilst other years use three wires.
There is also suggestion of mercury switches being used. The LA appears to be riveted together.

Without getting my hands on one, I find it difficult to understand how mercury switches and or a resister can go faulty.
More likely to have HR connectors or joints esp earths.

Do you have the LA the  guy pulled apart !?!?!??......

[jklumpp]

yes, that's the one.... though in my car it was relocated in the conversion (which made it a real headache to locate at first), and as I said before it was actually installed backwards!
I'll see if I can get some pictures.... haven't seen them for myself, but have been told they had a 'brown spot' in different locations.... I was picturing a circuit board, but could be wrong....

[Vettech]

Ummm thats interesting, my little knowledge makes me think it should be mounted as flat as possible on the centre lateral line of the vehicle.

I suppose now with their evolution, miniturization etc and their use in everything from cars to mobile phones, they could I suppose be, purpose build to conform to any requirement.

Pics would be good, if like me you cant get pics on our forum, feel free to email me.

Regards
Doug

[bfit]

  its one of these problems. 

[Hallsy]

I hope this is helpful.
I typed in “C4 corvette” in the C4 Corvette parts section of eBay (my son bought an 86 two weeks ago) and there’s a bloke (in the US) selling lots of parts...abs system,etc. It’s a donor car for a hot rod. He has a diagram of the wiring under the console with the part he is selling. He said he doesn’t know it’s purpose.
It’s listed as
“1994 Corvette C4 Parts -Sensor”
AU $53.19
obo

Hope it’s of interest, even just for the diagram.
Cheers,
Pete.

P.s. The diagram is in the “Item description” part.

[sabre]

I've got an 87, and I must admit, I've never had a code or any issues.

We are talking the unit screwed to the trans hump just in front of the shifter arent we. Covered in carpet, ac and radios etc etc.

Having typed the above and then going surfing, I now see plenty of people on the web with issues.

Because LA's started back in 84, they were rudimentary devices, now years later they have amplfiers, pizo's etc etc and are micro small.

So being a person who loves to pull things apart and see how they work, I'd love see inside the unit
The basic C4/87 electrical supp book, shows two switches in line, short or open, two wires, whilst other years use three wires.
There is also suggestion of mercury switches being used. The LA appears to be riveted together.

Without getting my hands on one, I find it difficult to understand how mercury switches and or a resister can go faulty.
More likely to have HR connectors or joints esp earths.

Do you have the LA the  guy pulled apart !?!?!??......

Unlikely to have a code error in an 87. No readable diagnostics in the early units. LA introduced in 93 with LT1. Output is analog signal with max and min at +/- 0,5 g. I believe 95/96 had a different sensor to 93/94.. Definitely not just switches or mercury contacts.

[jklumpp]

OK, here's some pics of the inside of the unit.
Looks like a small counterweight on a spring steel pendulum - moves left of right with G loads, within an electrical field which I guess varies the output/resistance... or something
the slight discolouring is on the mounts, not the board - so I'm not sure if that actually means anything or not.
I would need to desolder the joints to remove the board & look at the other side....

[Vettech]

Now thats why I have not seen a code, they only go from ~13 thru 53, and yours is different looking (externally) to the one fitted to the 87.

The 87 is clearly designated "Lateral Acceleration Switch" and its basic cct is shown as two (2) series switches (open at 》0.5g's). 

Now yours looks like its full of goodies, more goodies equates to more pieces that can fail. Obviously at least three wire connection.

[jklumpp]

I forgot to mention - I spoke to Steve @ SR Performance.
...good guy, and very willing to help, but unfortunatly he had no answers for me.... Said he has a customer who was having similar problems, but just decided to live with the ABS light on....

....The search for solutions continues - "The truth is out there"!

[jklumpp]

Rediscovered an interesting article I had forgotten I had read a while ago, from the QLD Corvette Club
http://www.qldcorvetteclub.com.au/tech/tech_talk/abs.htm

Most interestingly the author writes:
"The ABS goes through a self diagnostic routine the first time the vehicle passes through 5 kph after turning on the ignition. You have probably heard the pumps operating during this BITE test. (Built In Test Equipment operation) The lateral accelerometer will give a voltage of about 1.2V at 1g right, 4.2V at about 1g left and about 2.6V when the car is running straight ahead. If the control module reads in excess of 0.6g either way for more than 120 seconds, an error is indicated. Either the lateral accelerometer is faulty, or the car is lying on its side"

The readings at 1g would be simple to test - it's just a question of how to measure the voltage.... Anyone have any ideas? Or a wiring diagram that might help?

I have sent an email to the Queensland Corvette Club to see if I can get in contact with the author of the article, and see if he can provide any further advice on the accuracy of the specs he mentions, and how to measure the voltage.

[Vettech]

Yes - the self test is similar to my 03 Fairmont, as soon as it reaches ~5kph.