P38A 'ABS pump pressure sensor fault'

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JeremyAldermartenQC

JeremyAldermartenQC

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Lincolnshire
My 2000 2.5 DSE Auto shows the above fault when scanned. It won't clear. The brakes work fine and the pump is working fine and stopping starting as it should. I'm not sure where to go from here. Is there a sensor on the pump or is it just the pressure switch? The switch is clearly working. Someone had removed the three bulbs from the instrument cluster and muggins has only just twigged! Too busy looking at the glow-plug light!
 
What diag was used, if its flashing up abs fault one of the first things to check is the brake peddle switch it is double switching and needs the plunger setting, ie push peddle down and hold, pull out plunger then let peddle back up.
 
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It was a Snap-On professional scanner. Are you saying that the fault might not be with the pressure switch at all? You think that if I hold the plunger out and let the pedal up, it will reset something in the ECU control unit?
 
The p38`s are not really obd compliant and very few diags work on them and some throw up phantom faults, the switch is worth a try, cost nowght just pull the plunger out then let the peddle up, do you have a copy off Rave the workshop manual its a free download.
 
Update. I have replaced the warning light bulbs for ABS, traction control and brake. They are all lit all the time, as I expected. I still can't find Rave. I now know that a Saab owner (with the same ABS system) had the same fault message when the plunger on the brake light switch was sticking, so that confirms what you said about pulling the plunger down. Could you possibly give me a bit more info on that? Doesn't the plunger come down anyway, under spring pressure, when the brake pedal is depressed? I just want to be clear exactly what I'm trying to do there. From what you have said I just press the pedal, pull the plunger down, let go of it and let the pedal back up. Is that right? What does that do? If that doesn't do any good, what would you suggest I do next? Should I follow the error message 'ABS pump pressure sensor fault' and change the pump pressure switch, which , I understand, incorporates the sensor? If I change that, will I need to bleed the system? If it is easy to do, I could just try a known good sensor and then give it back if it doesn't sort it, I suppose. They seem to be very expensive. Thanks!
 
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The peddle switch is a two stage switch when the peddle is up it is completing one circuit for cruise control and something else then when you push peddle down it brakes that one and make another one for lights and abs, they do go wrong and for the cost of under £15 would rule that out.
if you have access to a known good pressure switch then worth a go, they do not go wrong that often hence the price if you can find one, a good second hand one is the way to go.
 
I got a second hand one for £95 12mnths ago. Touch wood been fine. Quite easy to change. Only needed to bleed at the resevoir
 
Regarding the brake pedal switch, have you checked it works correctly ? There should be 12V on pin-1 and then 12V on pins 2+3 when you press the pedal.
The connections are the same on pre-1999, and post-1999 models, but the connector number changed from C227 to C0075.

For the pressure sensor, check the wiring is below. Pins 2, 3, & 4 should be grounded depending on the system pressure.

upload_2021-2-4_11-36-43.png



Brake pedal Switch
upload_2021-2-4_11-30-18.png


Remove & Refit

upload_2021-2-4_11-28-45.png



upload_2021-2-4_11-28-16.png
 
Maybe. Check the switches work first. Not sure if the oil burner cruise has the vacuum pipe, but if it does check that too.

When refitting the switch hold the brake pedal down while you fit it. It's easier that way, and when you release the pedal the pedal will push the plunger to the correct depth.

It's probably easier the check the switching using a multimeter at the other end of the loom.
 
You can possibly check the switch off the car with a multi meter.
One circuit will go open circuit switch untouched and the other circuit closed.
The opposite will happen when the switch is compressed. ;)
 
JeremyAldermartenQC said:
Thanks, that is all excellent stuff. After fiddling with the brake light switch, the cruise has stopped working, so it looks like I need one!
Click to expand...

Have you downloaded and installed RAVE from the Technical Section. It has everything in it.

Pressure switches can be had cheaper from another car but I cannot remember which one.

When the bulbs on my dash were acting up I needed diag to clear the fault before they would go out.
 
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