ABS on H-reg 1990/91 SRi

[Telegram Sam]

During the last cold snap I all but had an accident as a result of losing control at low speed on what I suppose was a hidden icy patch. Subsequently it occurred to me that the ABS might have been (partly) responsible - the light had been coming on and the system needs to be checked out. Which triggered the thought: Are all ABS's equally good? One could upgrade to the most powerful brakes but without the means to control them in borderline situations (other than by prudence, driving skill and / or trusting to luck) the expense would be wasted. Can one upgrade the standard ABS?

[Robsey]

There are two specific ABS set ups on the Cavalier.
The early version has the control unit next to the passenger seat under a hump in the carpet.

Later ABS set ups are wholly located in the engine bay.

If your's has been flashing for some time, then it is obviously struggling with a speed pulse signal from one of the wheels, a damaged cable or in the worst cases, damp in the module.

I personally would stick with repairing the existing set up.
It is a lot of faff stripping out the old set up and fitting the later version.

When the ABS works, it works well regardless of which version you are using.

[Telegram Sam]

Tks, noted. I seem to remember that some time back there was some corrosion on the pick-up (?) near the road wheel and when this got sorted it was back to normal service. At least as far as removing the flashing was concerned though there is always the lingering suspicion that the system itself might not be 100%. Can this be tested (independent of the indicator?)

[Robsey]

I believe the older version cannot be diagnosed with the flash code / paper clip method of testing.

But the later version can be.
I will just check my diagnostic site notes.

[Robsey]

He is my post verbatim.

This is the general listing for the ABS Modules

(Courtesy of Andy Kirwan's Technical site - updated and edited)
Cavalier Mk3 and Calibra

To carry out a flash code diagnostic of the ABS system, short pins A and K on the diag plug and then turn on the ignition (engine not running).

If there are any stored fault codes, then the ABS Tell-tale light should flash out a two digit numerical sequence.

Early models which have the old ABS system where the control unit is located at the side of the passenger seat in a lump in the carpet do not usually have this fault code facility.

Check whether the diag plug has a wire at location K.

Calibra 2WD H reg (1990) models should have the facility to read out the codes.


16 LH Front Solenoid ( Relay & Connections )
17 RH Front Solenoid ( Relay & Connections )
18 Rear Solenoids ( Relay & Connections )
19 Solenoids Relay Circuits
25 Faulty Sensor toothed Ring
35 Pump Relay Circuits
37 Stop Lamp Switch ( Pedal Switch )
39 LH Front Speed Sensor ( Air Gap & Operation )
41 LH Front Speed Sensor ( Resistance & Connections )
42 RH Front Speed Sensor ( Air Gap & Operation )
43 RH Front Speed Sensor ( Resistance & Connections )
44 LH Rear Speed Sensor ( Air Gap & Operation )
45 LH Rear Speed Sensor ( Resistance & Connections )
46 RH Rear Speed Sensor ( Air Gap & Operation )
47 RH Rear Speed Sensor ( Resistance & Connections )
48 System Voltage High/Low ( Alternator & Battery )
55 Faulty ECU

[Envoy CDX]

If you're luck it will be the rings on the drive shaft have rotten and need replaced. £6 a side plus your time usually.

[Envoy CDX]

However - if you're reshelling into the N reg cav - you can pick and choose your bits.

[Telegram Sam]

I believe that I've got the lump between the passenger door and the sill But the man who has been servicing the car for the past umpteen years has got an electronic gizmo that can read fault codes and the like so hopefully he will be able to test it. At present the indicator is not showing whilst previously it was.

[Robsey]

Most diagnostic equipment looks at "powertrain" or P codes. It does not support early ABS diagnostics.

If anything, you are looking at Vetronix Tech 1 or the latest version of VauxCom / OpCom to read this module.

I cannot think of any off the shelf kit reading the abs codes using a 10 pin ALDL connector.
Most use 16 pin EOBD connectivity.
(Vauxcheck, Torque Pro and so on).

And as final consideration.
If pin K is not populated in the diagnostic plug, there will be no point of connection to the ABS module.

[James McGrath]

Sorry to hear about the accident, it wasn't serious I hope?

Am I right in saying there were 3 ABS systems? The original Bosch system with the module next to the passenger seat, a mid spec Bosch unit and a much cheaper unit introduced in 1994.

[Robsey]

There is the ABS-2E system in the early cars.
The relays for this are in a plastic box at the back of the engine bay.
This relay box also houses the relays and fuses for the air-con systems where fitted.
This is also the system where the control unit is in the space between the sill and the passenger seat.

Then there are two versions of the later ABS-2EH.
One with a sloped casing and one with a squarer / flat casing.
The sloped casing has relays that can be removed.
The fatter topped casing, the relays are non-removable.

[Telegram Sam]

Sorry to hear about the accident, it wasn't serious I hope?

It was a low-speed slow-motion loss of control near-miss - the kind where you have time to get a flash-back of your sinful life to date before the crunch, which in this case in spite of me being @ 45° to the intended direction of travel mercifully never came.

There is the ABS-2E system in the early cars.
This is also the system where the control unit is in the space between the sill and the passenger seat.

If this is what I think I've got, is it checkable?

[Robsey]

Haynes advises that the dealer has "dedicated equipment" to do this.

I will have to check in to TIS later to see what tests if any can be carried out.

According to the 1989 / 90 wiring schematics, there is no diagnostic line to Pin K in the X13 diagnostic plug.
So maybe they daisy-chain a specialist connector between the loom and the module.

[Robsey]

This is what TIS has to say -

Driving with ABS, Maintenance
Instructions
When the ignition is switched on, the "ABS" symbol in the instrument housing illuminates and then extinguishes after approx. 4 seconds. If the ABS telltale does not go out or if it comes on sporadically or stays on permanently during driving, there is a fault in the system.

Diagnosis of Fault:
With ABS-2S With Universal Checking Adapter KM-566-1, Checking Cable KM-566-2 or KM-566-11 and Multimeter MKM-587-A.

With ABS-2E / ABS-2EH With Diagnostic Switch KM-640 in switch position "K" or with TECH 1 in conjunction with Programme Module "OPEL / VAUXHALL 91-94 ECU or 87-94 ECU". After driving off, the ABS carries out further self-tests, which may be audible from noise from the return pump.
When braking hard, the vehicle remains free from wheel lock until it almost stops (approx. 4 km/h/2.5 mph), thus guaranteeing manoeuvrability.

Braking in the control range of the ABS is indicated to the driver by pulsing of the brake pedal, combined with noises from the return pump, warning him/her to adjust his/her speed to the road surface conditions.
If a defect occurs in the ABS, the ABS telltale lights up, however the conventional braking system remains fully operational. The vehicle should then be checked or repaired as soon as possible by a Franchised Opel/Vauxhall Dealer or by an authorised Opel/Vauxhall Service Workshop.

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Judging by this - If you have no wire at pin K of the diagnostic plug you must have the 2S set-up.
This will require a purpose built tool that connects to the ABS module directly.
So unless your garage has the correct Tech 80 / Tech 1 adapter, it will not be testable.

If you do have the wire at pin K, then you can flash up the fault codes as described in my earlier post.

[Telegram Sam]

Tks for the extensive research which you will understand that I will copy and paste to my garage man rather than try to figure it out for myself.

[Telegram Sam]

If electronic diagnosis proves to be impossible for the reasons stated then it ought to be possible to do a lo-tec mechanical check involving spinning the wheels individually (having removed any corrosion on the sensors) if I have understood correctly. I suppose that the ABS either works or doesn't work, that there is no half way house. The indicator light can't make up its mind whether to light up or not depending on what day it is.

[Telegram Sam]

Hopefully replacing what has now turned out to be a broken / corroded front o/s sensor ring will solve the problem without having to resort to K pins and paper clips and things. I am told that it is not possible to upgrade my ABS

[Robsey]

I would beg to differ with your garage.

I cannot see why you cannot upgrade to a later specification ABS.

The question is cost effectiveness and being worth the hassle.

I would say stick with what you have.

I suppose the easiest method of upgrade, is to strip out ALL of your current ABS system except the wheel sensors and the wires going to them.

Then go through all the hassle of fitting and bleading the necessary modulator and control unit along with associated relays and fuses.

At the end of the day, all that you would probably gain is diagnostics via the paper clip method.

All other aspects of the system will work exactly the same.

[Telegram Sam]

As you say it's probably not worth the hassle if at the end of the day there would be no greater effectiveness and if most if not all failures can be identified by having a quick look at the front sensor rings when the car is on a ramp. I believe that with more modern systems you can get traction control and other goodies which are out of bounds for cars of my vintage.

[Robsey]

Indeed on modern systems, you can have traction control, cornering brake control and electronic stability programs.

My Vectra-C has all these functions, but 15 seconds of wheel spinning on snow or ice, and the whole lot shuts down.

I live on a steep hill, so wheel spinning in wintery conditions is not particularly rare.

So - some modern systems are not particularly any better than the old ones.

I can say that the ABS on my Cav has worked perfectly every time it has been called into action.
Although the noise and pulsing pedal did give me a few brown trouser moments in the early days. But only because I thought I had broken the car.

[Telegram Sam]

My Vectra-C has all these functions, but 15 seconds of wheel spinning on snow or ice, and the whole lot shuts down.

ABS sensor ring replaced. Hopefully problem solved.

[Robsey]

Hopefully job done.

Regarding traction control.
Some of the bigger engined models did have an option of traction control.
I have a "TC" button in my Cav - In standard Cav configuration it is usually mounted between the heated seat switches below the ashtray.

Alas my TC switch button acts as a total closure button for my Meta / Toad car alarm system.

[Telegram Sam]

My humble SRi doesn't have as far as I know traction control, heated seats / switches, Meta self destruct or ejector seat buttons. There is an ashtray somewhere.

[Robsey]

I would not sat that SRi is a "humble" spec.
It is one of the highest specifications in the "standard range" sales brochures.

Non-standards being Diplomat, Turbo and GSi.

The SRi is 2 or 3 places above my LS model.
In my model year the hierachy in the brochure was,
Envoy, Expression, LSi, GLSi, CD, SRi

And as we speak, my LS does not have an interior, rear doors or tail gate.

Not quite sure the relevance to Traction Control and Teleport... but hey ho.
Ha ha.

[Telegram Sam]

Does wonders for my personal ego that

"And as we speak, my LS does not have an interior, rear doors or tail gate." May be after we have finished our speak? Worth a check.