P38A Intermittent ABS pump fault - hence no brakes, fitted new R17 and accumulator

Hi folks,

So the other day I was driving to work and had to pass some vehicles parked on my side of the road. As I went along a car started coming in the opposite direction, so I looked for somewhere to pull in. Anyway, imagine my shock when I had no brakes (turns out I had no power assist), with a car coming towards me!!!

Managed to get it stopped and noticed that the yellow ABS and red brake warning lights were on (1995 DT model so don't think I have TC, it's manual too just so you know).

Parked it up at home and had a look that night. Ignition on and ABS pump fired up, for about 30 seconds and then cut out. Every press of the brake results in the pump coming on for about 1-2 seconds. So I thought it was an accumulator issue. Ordered one and fitted it but when I switched on the ignition, no pump, even after multiple pushes of brake pedal it would not come on.

So I'm now thinking an intermittent power issue. So ordered a new PRC9566 relay 17. When I came to fit it last night I checked the old one by switching on ignition. Sure enough ABS pump came on. Changed the relay and tried afterwards, still working. So took it for a little drive. All fine, no lights, plenty of brakes.

Tried it this morning and again no pump on ignition switch on! Tried pumping brakes to see if it would cut in but nothing.

So.......my next thing to consider would be a failing pressure switch (the green one), or; and maybe cheaper, a new fuse box??? I've read that the fuse box contacts can burn out and cause this issue. Would it be worthwhile trying to wiggle the relay at all or is this pointless (won't cost me anything ).

Is there anything else to consider? I don't think it's the ABS pump, it sounds fine when working, my thoughts are intermittent electrical or hydraulic pressure issue. Would it be worthwhile giving the brakes a good bleed, as per manual?

All the discs/pads are in good nick as I've changed them in the last couple of years and don't do many miles (15,000 in 6.5 years).

Any thoughts greatly appreciated.

Gary

Try relay 2 fuse 27.

Tried them both Wammers.

Tried a new relay 2 and fuse 27 is fine. In fact all fuses look fine.

Tonight there is no getting the pump on at all

Just wondering if I can bypass the circuit to apply 12v straight to pump to see if it’s electrical or hydraulic/pressure related???

gazcabs said:

Tried them both Wammers.

Tried a new relay 2 and fuse 27 is fine. In fact all fuses look fine.

Tonight there is no getting the pump on at all

Just wondering if I can bypass the circuit to apply 12v straight to pump to see if it’s electrical or hydraulic/pressure related???

Click to expand...

Try relay 15 ignition relay.

If relay 15 was the culprit, would I be able to start the car? The car starts fine you see, just no ABS pump....

gazcabs said:

If relay 15 was the culprit, would I be able to start the car? The car starts fine you see, just no ABS pump....

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Try it.

Well did relay 15 sort it?

Not had a chance to look into it yet. Probably not till weekend now.

Deep joy!!!

Nothing.......it’s not relay 15. Apparently there’s a test where you can earth out the pressure switch to see if the pump runs, if it does then chances are it’s the pressure switch.

I just hope it is that now and not the pump. Going to spend the next week fault finding the electric side to double check it’s not that. In other words make sue that 12v is getting to the pump/switch.

gazcabs said:

Nothing.......it’s not relay 15. Apparently there’s a test where you can earth out the pressure switch to see if the pump runs, if it does then chances are it’s the pressure switch.

I just hope it is that now and not the pump. Going to spend the next week fault finding the electric side to double check it’s not that. In other words make sue that 12v is getting to the pump/switch.

Click to expand...

The pressure switch is a known failure item. Hard to source a new one and expensive, but if memory serves me correctly, there is a SAAB part that does the job. (very old so memory not too good these days!)

Yeah I can get one from the states for £108 all in, brand new. Reviews left on Amazon have mentioned a lot of buyers fitting it to P38's, so pretty confident it's the right one, ACDelco, mentions GM which to be honest is who owned SAAB anyway.

Just gonna try and see if there's a fault come up, if I can get it read anywhere.....

gazcabs said:

Yeah I can get one from the states for £108 all in, brand new. Reviews left on Amazon have mentioned a lot of buyers fitting it to P38's, so pretty confident it's the right one, ACDelco, mentions GM which to be honest is who owned SAAB anyway.

Just gonna try and see if there's a fault come up, if I can get it read anywhere.....

Click to expand...

Should have had it on diag a long time ago may have saved you few bob. Guessing on these is a bank balance drainer.

Maybe, although I've only actually bought a new accumulator so far, which it needed anyway (pump on every time brake pedal was pushed), so not a complete waste.

I don't want to spend anything else until I'm certain what it is.................trying to get someone nearby to read the faults isn't that easy.

gazcabs said:

Maybe, although I've only actually bought a new accumulator so far, which it needed anyway (pump on every time brake pedal was pushed), so not a complete waste.

I don't want to spend anything else until I'm certain what it is.................trying to get someone nearby to read the faults isn't that easy.

Click to expand...

Are you absolutely sure it is not relay 15. How did you check it?

I just swapped it with a different one, the wipers I think are the same, well same pin layout and numbering and same diagram.

Had the faults read tonight (by the way the pump was working last night, for about 15 mins, then went again).

I’ll put a picture of the faults up later tonight.....

This was the first read:

ECU failure and no voltage etc, also 2 sensors with air gap too large

But we then cleared them and there was nothing recorded, even went for a little drive.

All 4 wheel speed signals reading very similar values

But still the 2 lights (abs and brake warning) were on. I might not have TC on mine as it’s an early 95 model

Even came up with cruise control switch fault - don’t even have it, and glow plug fault, which wasn’t there initially

gazcabs said:

I might not have TC on mine as it’s an early 95 model

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What's the code on your brake modulator?

I’ll have to check that one another day, cars at my mates still.

Will that tell me if it has TC?

gazcabs said:

I’ll have to check that one another day, cars at my mates still.

Will that tell me if it has TC?

Click to expand...

Yes.